PHYS 221 Multiple Choice Questions
A bass has a gas-filled sac or air bladder that allows it to float motionless below the surface of the water. What is the bass's average density?
The density of water.
Compare the flight of two golf balls given the same impulse by the club. Which ball will travel a larger distance?
The dimple ball
Assume a disk and a ring with the same radius roll down an incline of height h and angle theta. If they both start from rest at t = 0, which one will reach the bottom first?
The disk
Which of the following observations about the frictional force is incorrect?
The magnitude of the force of static friction is always proportional to the normal force.
During a July 4th firecracker party, a pop bottle rocket lying still on the ground explodes, sending fragments everywhere. If the momentum of the pop bottle rocket (ignore friction!) initially at rest is conserved during an explosion, what can be said about the kinetic energy of various fragments after the collision?
The total kinetic energy afterwards is greater than what it was initially.
The P-V diagram below shows six curved paths (connected by vertical paths) that can be followed by a gas. Which two of them should be part of a closed cycle if the net work done by the gas is to be at its maximum positive value?
c and e
When water flows smoothly in a straight hose, its viscosity causes the water to
convert some of its kinetic energy into thermal energy.
In any process, the maximum amount of mechanical energy that can be converted into thermal energy
is 100%.
Heat is added at a rate of 10.0 kJ/min to a 0.5 kg solid sample starting at t = 0 min. What is the melting temperature of the sample? Note the units of the answers!
283 K
When a tube of diameter d is placed in water, the water rises to a height h.If the diameter were half as great, how high would the water rise?
2h
A car accelerates down a straight highway. Which of the free-body diagrams shown best represents this situation?
3
The position of a mass on a spring as a function of time is shown below.Consider the time corresponding to point P.At this time the mass
positive velocity and negative acceleration
Substance A has a density of 2.0 g/cm3and substance B has a density of 3.0 g/cm3. In order to obtain equal masses of these two substances, the ratio VA/VBof the volume of A to the volume of B has to be equal to
3 : 2
Three identical wheels are all spinning with the same angular velocity ω. The total angular momentum of the 3-wheel system has magnitude L. One of the three wheels is flipped upside-down, while the magnitude of its angular velocity remains constant. What is the magnitude of the new angular momentum of the 3-wheel system ?
(1/3) L
Rockets receive their forward propulsion through
pushing against the exhaust.
Pure sound notes from two sources make the molecules of air at a location vibrate simple harmonically in accordance with the equations y1 = 0.008 sin (604 π t) and y2= 0.007 sin (610 π t), respectively. The number of beats heard by a person at the location will be
3
Two dice are thrown. Let the macrostatebe the sum of the two numbers on the top faces. What is the multiplicity of the macrostate"4"?
3
Heat is added at a rate of 10.0 kJ/min to a 0.5 kg solid sample starting at t = 0 min.A temperature versus time diagram is shown.In which region(s) is the liquid phase present?
B and C
Heat is the transfer of disordered energy from one system to another. Is it possible for heat to enter a system while the temperature of the system does not change?
Yes
Is it possible to have motion in the absence of a net force?
Yes
Two balls of putty of equal mass approach each other from opposite directions with equal speeds. They stick together and come to rest. Was momentum conserved in this collision?
Yes
Suppose you are on a cart, initially at rest on a frictionless, horizontal track. You throw a series of identical balls against a wall that is rigidly mounted to the cart. If the balls are thrown at a steady rate and bounce straight back, is the cart put into motion?
Yes, it starts to move to the left keeps on gaining speed.
Can an object's velocity change direction when its acceleration is constant?
Yes, this is possible, and a rock thrown straight up is an example.
The radius of the aorta is ~ 10 mm = 10-2 m and the blood flowing through it has a speed ~ 300 mm/s = 0.3 m/s. A capillary has a radius ~ 4×10-3 mm = 4×10-6 m, but there are literally billions of them. The average speed of blood through the capillaries is ~ 5×10-4 m/s. (i) Calculate the effective cross sectional area of the capillaries and (ii) the approximate number of capillaries.
(i) 0.188 m^2, (ii) 3.75*10^9
A vector of magnitude 20 is added to a vector of magnitude 25. The magnitude of this sum might be
12
At which temperature do the molecules of an ideal gas have 3 times the kinetic energy they have at 32oF?
546 oC
A star with a surface temperature of 6000 K appears yellow in color. A star with a surface temperature of 4000 K will
appear reddish on color.
In any process, the maximum amount of heat that can be converted into mechanical energy
depends on the intake and exhaust temperatures.
In order to do a positive amount of work you must
exert a force and move in the direction of the force.
A drum major is given two batons, one gold and one plastic. He is told that both batons have the same mass. He tries spinning each one and finds that the plastic one is much easier to start and stop spinning. He correctly concludes that the plastic baton, in comparison to the gold baton
has more of its mass distributed towards the center.
Your class is rather unhappy with the instructor, and they pitch in and decide to fund a sabbatical for him to go to Mars. Unbeknownst to the students the following semester, the instructor has made long distance course arrangements so the "show can go on". The instructor begins talking about mass, weight and related things. He correctly makes which following statement:
his mass is still essentially unchanged but his weight is less than on earth.
The SI units for viscosity are
kg/(m-s)
A hand moves to produce a periodic wave. You are making a movie. You freeze the movie and get this snapshot. If you advance the movie one frame, the knot at point A would be
lower.
The volume of a gaseous sample is increased from V1 to V2 in three different ways. A-->B: isobaric process A-->C: isothermal process A-->D: adiabatic process Then the work done by the gas is
maximum in the isobaric process.
Two thermometers, one calibrated in oF and one in oC, are used to measure the same temperature. The numerical reading on the Fahrenheit thermometer
may be equal, higher or lower than that on the Celsius thermometer, depending on the temperature.
Dimples on a golf ball hit without spin
reduce drag.
Two cylindrical artificial bones are made of the same material and length, one with twice the radius as the other. When the two have the same tension force applied, the larger bone stretches by what factor compared to the smaller bone
0.25
Another scheme to catch the roadrunner has failed and a safe falls from rest from the top of a 30.0 m high cliff toward Wile E. Coyote, who is standing at the base. Wile first notices the safe after it has fallen 15 m. How long does he have to get out of the way?
0.72s
In how many of the following situations does the car have a westward acceleration? -- The car travels westward at constant speed. -- The car travels eastward and speeds up. -- The car travels westward and slows down. -- The car travels eastward and slows down. -- The car starts from rest and moves toward the east.
1
An apple at rest weighs 1 N. Now assume the same apple is in free fall near the surface of Earth. Neglect friction. The net force on the apple while it is in free fall is
1 N
The mass of atoms is often given in atomic mass units (u). (1 u = 1.66*10-27 kg) The mass of a hydrogen atom is 1 u, the mass of a carbon atom is 12 u, and the mass of a oxygen atom is 16 u. Calculate the mass, in kg, of a water molecule, H2O.
2.99*10^-26
Detergents or wetting agents
reduce the angle of contact.
When blood flows into an aneurysm
the speed decreases and the pressure increases.
Two carts A and B are moving towards each other as shown in the diagram. They collide and come to rest at the point of impact. From this observation we can conclude that the carts
were moving with momenta equal in magnitude and opposite in direction.
A mass m is lowered gently onto a vertical spring of length L with spring constant k until it just touches the spring. Let y be the distance the spring is compressed and v be the velocity of the mass. The mass is released from rest. Which of the following is the equation for conservation of energy?
½mv^2 + ½ky^2 + mg(L - y) = mgL
A 2 kg block of wood is floating in water. What is the magnitude of the buoyant force acting on the block?
19.6 N
In an inertial frame, an object cannot remain at rest unless which of the following holds?
The net force acting on it is zero.
While a guitar string is vibrating, you gently touch the midpoint of the string to ensure that the string does not vibrate at that point. The lowest-frequency standing wave that could be present on the string
vibrates at twice the fundamental frequency.
As a bacterium swims through water it propels itself with its flagella so as to overcome the frictional drag forces and move at, more or less, constant velocity of 100 micrometer/s for periods of time. If the frictional drag force on a bacterium is 0.1 N, how much work does the bacterium do in 1 s?
10 microJoule
Two blocks of mass M and 3 M are placed on a horizontal frictionless surface. A light spring is attached to one of them, and the blocks are pushed together with the spring between them. A cord holding them together is burned, after which the block of mass 3 M moves to the right with a speed of 5 m/s. What is the speed of the block of mass M?
15 m/s to the left
A bicycle's wheels have a radius of 33 cm. The bicycle is traveling at a speed of 6.5 m/s. What is the angular speed of the front tire?
19.7 rad/s
A 1 kg rock is suspended by a massless string from one end of a meter stick at the 0 cm mark. What is the mass m suspended from the meter stick at the 75 cm mark if the system is balanced?
2 kg
Suppose you do 1000 J of work on a 4 kg object, and all the work goes into lifting it above the ground. How high above the ground will the object be when all the work has been done?
25 m
A person walks first at a constant speed of 6 m/s along a straight line from point A to point B and then back along the line from B to A at a constant speed of 4 m/s. What is her average speed over the entire trip? Hint: Assume the distance between A and B is d. How much distance does the person cover on her trip? How long does it take her to cover this distance?
4.8 m/s
A beaker containing 5.0 kg of water is on a weighing scale. A 0.8 kg block of metal that has density 8*103 kg/m3 that is attached to a string is lowered completely into water without touching the bottom. Assume that the beaker is massless, and water has density 103 kg/m3, and g = 10 m/s2. What is the reading on the scale?
51 N
A 2 kg mass is at x = 0 m, y = 2 m, and a 3 kg mass is at x = 2 m, y = 0 m. The x- and y-coordinates, respectively, of the center of mass of this system are
6/5 m, 4/5 m
A microwave oven is rated at 1000 W. At sea level, how long will it take to bring a cup of water (250 ml) to boil from room temperature (20 °C)? Assume the specific heat capacity of the cup itself is negligible. (for water: cw = 4190 J/(kg K), 1 ml = 1 cm3 = 1 g)
84 s
A gas is in a container with a piston lid and is taken from thermodynamic state, 1, to a new thermo-dynamic state, 2, by several different paths, A, B, and C, in the P-V plane. The internal energy of the gas increases during the process. The work done by the gas is largest for path
A
The picture below shows 5 blocks. The blocks have equal volumes but different masses. The blocks are placed in an aquarium tank filled with water and blocks 2 and 5 come to rest as shown in the figure. Which answer is correct?
Block 3 will come to rest in the same position as block 5.
You drop an object from a bridge and simultaneously, you throw a-other object downwards at 10 m/s. As the objects are falling, which object has the larger acceleration? (Ignore air resistance.)
Both objects have the same acceleration.
A small metal cylinder rests on a circular turntable, rotating at a constant speed, as illustrated in the diagram above. Which of the sets of vectors best describes the velocity, acceleration, and net force acting on the cylinder at the position indicated in the diagram?
D
Suppose you are riding on a merry - go - round and you move out to the edge. What happens to the rotational rate of the system?
It decreases because angular momentum is conserved and the moment of inertia increases.
A clever physics student is able to sneak a scale on a popular ride at an amusement park. Before the ride begins to move, the scale reads 700 N for the student's weight. As the ride lifts, it initially accelerates upward at 3 m/s2. At the top, the riders are held in suspense before the gondola is allowed to free fall downward with acceleration equal to g. What should the scale read for the student's apparent weight during the lift and the fall?
Lift: 910N, Fall: 0 N
A DVD is rotating with an ever increasing speed. How do the angular velocity, angular acceleration, tangential velocity, and tangential acceleration compare at points P and Q?
Points P and Q have the same angular velocity and the same angular acceleration.
An object on the end of a spring is oscillating in simple harmonic motion. If the amplitude A of oscillation is doubled, how does this affect the oscillation period T and the object's maximum speed vmax?
T remains the same and vmax doubles.
A gas is in a container with a piston lid and is taken from thermodynamic state, 1, to a new thermo-dynamic state, 2, by several different paths, A, B, and C, in the P-V plane. The internal energy of the gas increases during the process. The internal energy change is largest for path
The internal energy change is the same for the three paths.
You fill two identical mugs with coffee, but the coffee in one mug is at a higher temperature than that in the other mug. You place the two mugs simultaneously in a microwave oven and turn it on briefly. As a result, you add 1 Joule of thermal energy to each mug. Which mug experiences the larger increase in entropy (if any)?
The mug containing the colder coffee experiences the larger increase in entropy.
A box is at rest on a flat table. Which of the following is true?
The normal force and the gravitational force are equal in magnitude and opposite in direction.
Suppose that there is a partial blockage of the aorta, which normally pumps about 5 L of blood per minute. If the diameter of the aorta were reduced by 30%, what increase in blood pressure gradient would be needed to obtain the normal flow rate? (Assume that Poiseuille's law applies.)
The pressure gradient would have to increase by a factor of 4.2.
Blood flows through a section of a horizontal artery that is partially blocked by a deposit along the artery wall. A hemoglobin molecule moves from the narrow region into the wider region. What happens to the pressure acting on the molecule as it moves from the narrow to the wider region?
The pressure increases.
Which of the following assumptions is not made in the derivation of Bernoulli's equation?
There is negligible gravity.
Why do elastic balls bounce so well?
They store energy through compression, like a spring.
At a given temperature
all the molecules in a gas have the same average kinetic energy.
A grandfather clock is running slow. The period of its pendulum is too long. To shorten the period and make the clock run faster, you should.
decrease the length of the pendulum.
Assume we can change the equilibrium state of a system via two different processes. Assume that the initial and the final state are the same. Which of the quantities ΔU, ΔQ, ΔW, and ΔT must be the same for the two processes?
only ΔU and ΔT
After clearing the bar on a high jump, you land softly on a giant mattress. Landing on a mattress is more comfortable than landing on a sand heap of equal size because
the force the mattress exerts on you to stop your descend is much less than the force the sand heap would exert on you.
A beaker is filled with water to the rim. Gently you place a toy duck in the beaker and some of the water spills out. The duck floats. The weight of the beaker with the duck floating in it is
the same as its weight before adding the duck.
You are watching a semi truck bounce up and down on a spring. (Yep it's a toy.) At the topmost point in the truck's path,
the truck's velocity is zero but its acceleration is downward.
An object is thrown straight up. At the top of its path
the velocity is zero and the acceleration is equal to g pointing down.
Newton's 3rd law is also called the law of action and reaction. The "reaction" force does not cancel the "action" force because
they act on different bodies.
How many nodes and antinodes are shown in the standing wave below?
three nodes and two antinodes
The four things that affect the amount of water flowing through a hose are
water viscosity, hose length, inlet and outlet pressure difference, and hose diameter.
A man jumps off of a bridge towards a river below. As he falls, he feels himself spinning forward (clockwise in diagram). To keep from hitting the water head-first, the man should
windmill his arms clockwise to keep upright.
Suppose you have a very long straw that can reach from a cup of water on the ground level to the top of a very tall building. When you use a pump to suck on the straw in order to bring water up,
you can bring the water up to only a maximum height in the straw, when the pressure of the water column is approximately equal to the atmospheric pressure.
The graph shows the acceleration of a cart with mass m = 0.555 kg, moving initially with constant speed, as a function of time, as a force F = ma stops the cart. Estimate the initial momentum of the cart in units of kgm/s.
~0.6
Refer to the diagram below. Blocks I and II, each with a mass of 1 kg, are hung from the ceiling of an elevator by ropes 1 and 2. What is the force exerted by rope 1 on block I when the elevator is travelling upward at a constant speed of 2.0 m/s?
~10 N
A string is clamped at both ends and plucked so it vibrates in a standing wave between two extreme positions as shown by the dashed lines below.If the string has length L and the frequency of oscillation of this mode is f, the speed of the waves on that string is
(2/3)fL
A container with a piston-lid contains an ideal gas at temperature Ti = 27 oC (300 K) and a volume V0. The temperature is increased to Tf = 127 oC while the pressure is kept constant. What is the new volume?
(4/3) V0
(A) Can two force vectors of unequal magnitude sum to zero net force? (B) Can three force vectors of equal magnitude sum to zero net force?
(A) no, (B) yes
A ball is thrown vertically upward, and as it comes down, it is caught at its initial position. Which of the following graphs best represents the velocity of the ball as a function of time?
(C)
Sam and George are riding in separate cars on the freeway. The lanes they are driving in are adjacent. We choose our coordinate system so that both are traveling into the positive x-direction. Sam travels at 65 mph and George travels at 72 mph. (a) What is Sam's velocity relative to George? (b) What is George's velocity relative to Sam?
(a) -7 mph, (b) 7 mph
A block slides on a track from A to B to C to D. The section from A to B to C is frictionless, but for the section from C to D the coefficient of friction is not zero. Is the block's mechanical (ordered) energy increasing, decreasing, or constant in (a) region AB, (b) region BC, and (c) region CD?
(a) constant (b) constant (c) decreasing
An object is dropped from rest at t = 0 into a viscous fluid. Which of the following best describes the object's speed as a function of time?
(b)
Refer to the heat engine experiment in Studio session 11. The PV diagram for one cycle of the engine is shown below. The path on the diagram connection points (1) and (2) corresponds to which part of the cycle? (a) The air chamber is placed into the ice water. The temperature decreases and the gas contracts. The volume of air in the chamber decrease. (b) A mass is placed on the platform. The weight of the mass increases the pressure at constant temperature. The volume of air in the chamber decrease. (c) The air chamber is placed into hot water. The temperature rises and the gas expands. The volume of air in the chamber increases (d) The mass is removed from the platform. Removing the weight decreases the pressure at constant temperature, The volume of air in the chamber increases.
(c)
Two identical carts labeled A and B are initially resting on an air track. The coordinate system for describing the system is shown. The cart on the right, cart B is given a push to the left and is released. The clock is then started. At t = 0, cart B moves in the direction shown with a speed v0. They hit and stick to each other. The graphs below describe some of the variables associated with the motion as a function of time. For the experiment described and for each item in the list below, identify which graph is a possible display of that variable as a function of time assuming a proper scale. "The system" refers to carts A and B together. (i) the momentum of cart A (ii) the momentum of cart B (iii) the total momentum of the system (iv) the total kinetic energy of the system
(i) #1, (ii) #3, (iii) #6, (iv) #2
A wave travelling in the +x direction is described by the equationy = 0.1 sin (10 x − 100 t),where x and y are in meters and t is in seconds.Calculate(i ) the wavelength, (ii) the period,(iii) the speed, and(iv) the amplitude of the wave
(i) 0.63 m, (ii) 0.063 s, (iii) 10 m/s, (iv) 0.1 m
For a sound wave of frequency 440 Hz, what is the wavelength (i) in air (propagation speed, v = 3.3 * 102 m/s)? (ii) in water (propagation speed, v = 1.5 * 103 m/s)?
(i) 0.75 m, (ii) 3.41 m
A wave travelling in the +x direction is described by the equationy = 10 m sin (5 x − 20 t)where x and y are in meters and t is in seconds.Calculate(i) the wavelength, (ii) the period,(iii) the speed, and(iv) the amplitude of the wave.
(i) 1.26 m, (ii) 0.314 s, (iii) 4 m/s, (iv) 10 m
Organ pipe B is open at both ends and is half as long as organ pipe A, which is open at one end, as shown. What is (i ) the ratio of their fundamental wavelengths λA: λBand(ii) the ratio of their fundamental frequencies fA: fB?
(i) 4:1 (ii) 1:4
A ball is launched up a ramp by a spring as shown in the figure. At the time when the clock starts, the ball is near the bottom of the ramp and rolling up the ramp as shown. It goes to the top and then rolls back down. For the graphs shown below, the horizontal axis represents the time. The vertical axis is unspecified. Select the number of the graph that could correctly represent (i) the x-component of the ball's position, (ii) the x-component of the ball's velocity, (iii) the x-component of the ball's acceleration.
(i) 8, (ii) 3, (iii) 2
Four different mice (labeled A, B, C, and D) ran the triangular maze shown below. They started in the lower left corner and followed the paths of the arrows. The times they took are shown below each figure, (i) Which mouse had the greatest average speed?(ii) Which mouse had the greatest average velocity?
(i) B, (ii) A
A toy car is moving on a straight track along the positive x-axis. It stays to the right of the origin. For the situations described below, choose the letter of the correct acceleration vs. time graphs that corresponds to the motion described. (i) The car speeds up at a constant rate, moving away from the origin. (ii) The car slows down at a constant rate, moving away from the origin. (iii) The car moves at a constant speed toward the origin.
(i) B, (ii) D, (iii) E
Two carts on an air track are pushed towards each other. Initially, cart 1 moves in the positive x direction and cart 2 moves in the negative x direction. They bounce off each other elastically. The graphs at the right describe some of the variables associated with the motion as a function of time. For the experiment described and for each item in the list below, identify which graph is a possible display of that variable as a function of time. If none apply, choose N (for none). (i) the momentum of cart 1 (ii) the position of cart 1. (iii) the position of cart 2.
(i) D, (ii) B, (iii) N
A cart can move to the right or left along a horizontal track (the positive part of the x axis) as shown in the figure below. Neglect friction. A force is applied to the cart. Choose an appropriate force versus time graph for each statement below. (i) The cart moves toward the right (away from the origin) with constant velocity. (ii) The cart moves toward the right and is speeding up at a steady rate (constant acceleration). (iii) The cart moves toward the left and is speeding up at a steady rate (constant acceleration). (iv) The cart moves toward the right, speeds up and then slows down.
(i) E, (ii) A, (iii) B, (iv) G
The position versus time graph represents the motion of an object moving along a straight line. What is the instantaneous velocity of the object at t = 14 s?
-(5/3) m/s
By how much does the entropy of 100 g of water at 0 oC change if the water is slowly converted into ice at 0 oC? The latent heat of fusion is 80 kcal/kg.
-0.029 kcal/K
Suppose you are standing on a bathroom scale while riding in an elevator. For a moment the scale reads 160 lb = 712 N while your actual weight is 180 lb = 800 N. What is your (and the elevator's) acceleration? (Let g = 10 m/s2.)
-1.1 m/s2
A centrifuge in a medical laboratory rotates at an angular speed of 3600 rev/min. When switched off, it rotates 50 times before coming to rest. What is the constant angular acceleration of the centrifuge?
-226.2/s^2
A boy holds a 40 N weight at arm's length for 10 s. His arm is 1.5 m above the ground. The work done by the force of the boy on the weight while he is holding it is
0
If you double the radiating surface area of a star while keeping its temperature constant, its power output increases by a factor of
2.
What is the approximate period of the sound waves shown here? (The speed of sound in air is ~340 m/s.)
0.0037 s
Blood and water have the same contact angle with glass. The density of blood is 5% higher than that of water. (ρblood= 1.05 ρwater) While you make your capillary action measurements you find that water rises in the same tube a factor 1.69 higher than a blood sample. The surface tension of water at the same temperature is 0.073 N/m. What is the surface tension of the blood sample?
0.045 N/m
A 40 kg child standing on a frozen pond throws a 0.5 kg stone to the east with a speed of 5 m/s. Neglecting friction between the child and the ice, what is the recoil velocity of the child?
0.0625 m/s west
A ball initially at rest is hit by a club. It is in contact with a club for 6.0*10-3seconds. Just after the club loses contact with the ball, the ball's velocity is 2.0 m/s. If the ball's mass is 50 g, what is the magnitude of the impulse the club gives to the ball?
0.1 kg m/s
A 5.00 kg mass sliding along a horizontal frictionless surface at 2.00 m/s collides with a 1.00 kg stationary mass. After the collision the two masses stick together and contact a light Hooke's-law spring with spring constant k = 1000 N/m. What is the maximum compression (in m) of the spring?
0.13 m
A horizontal external force of 10 N acts on a 4 kg box that slides across a surface with constant velocity. What is the coefficient of kinetic friction μk between the box and the surface? (Let g = 10 m/s2.)
0.25
A 65 kg physics student is at rest on a 5 kg sled that also holds a chunk of ice with a mass of 2 kg. The student throws the ice horizontally with a speed of 10 m/s relative to the ground. If the sled slides over a frozen pond without friction, how fast (in m/s) are the sled and student traveling with respect to the ground after throwing the chunk of ice?
0.286 m/s
An intravenous blood plasma drip enters a vein in the patient's arm from a bag raised a height h above the vein. If the diameter of the 5 cm long needle is 0.5 mm, use Poiseuille's law to find the height h that results in a 5 cm^3/min flow rate. (Assume the blood pressure in the arm is 18 torr = 2392 Pa and the viscosity of the blood plasma is 1.5*10^-3 Pa-s.)
0.66 m
The velocity versus time graph to the right represents the motion of an object moving in one dimension. What is the object's average acceleration between t = 0 and t = 6 s?
0.67 m/s2
A boy has a mass of 20 kg. He is standing on an icy pond, when a "friend" throws a 2 kg ball at him with horizontal velocity of 8 m/s.If the boy catches the ball, how fast will he be moving?
0.727 m/s
Suppose the earth's polar ice caps melted, sending water towards the equator and increasing the moment of inertia of the earth to 1.1 times its present value. The angular velocity of the earth would be
0.909 times its present value.
A 90 kg man and a 10 kg girl are initially 10 m apart. They are connected by a massless rope, and are sitting on a frictionless horizontal surface. The man pulls on the rope until they meet. Where do they meet?
1 m away from the initial position of the man.
Angular speed is measured in units of s-1, which is rad/s.How many degrees correspond to 1 radian?
1 rad = 57.3 degrees
Which of the following wave functions describe a wave that movesin the -x-direction? 1. y(x,t) = A sin (-kx-ωt) 2. y(x,t) = A sin (kx+ ωt) 3. y(x,t) = A cos(kx+ ωt)
1, 2, and 3
When the body requires an increased blood flow rate in a particular organ or muscle, it can accomplish this by increasing the diameter of arterioles on that area. By what factor must the diameter of an arteriole increase to double the volume flow rate of blood, all other factors remaining the same?
1.19
A sample of water at 0 oC is slowly converted into ice at 0 oC? The entropy of the sample changes by ΔS = -0.586 kcal/K. What is the mass of the sample?The latent heat of fusion is 80 kcal/kg.
2 kg
When the body requires an increased blood flow rate in a particular organ or muscle, it can accomplish this by increasing the diameterof arterioles on that area. By what factor must the diameter of an arteriole increase to double the volume flow rate of blood, all other factors remaining the same?
1.19
Two particles of masses 2 g and 8 g are separated by a distance of 6 cm. The distance of their center of mass from the heavier particle is
1.2 cm
How much negative pressure, with respect to atmospheric pressure, do your lungs have to produce, so you can you suck water through a straw to a height of 12 cm?
1.2 kPa
An ideal spring has a spring constant of 400 N/m. It is compressed by 0.1 m.How much work must an external force do to further compress the spring from 0.1 m to 0.13 m?
1.38 J
A vibrating source generates a harmonic wave on a string under constant tension. If the power delivered to the string is doubled, by what factor does the amplitude change?
1.41
Two particles of masses 2 g and 6 g are separated by a distance of 6 cm. The distance of their center of mass from the heavier particle is
1.5 cm
A car has a maximum acceleration of 4.5 m/s2. What would be its maximum acceleration while towing a second car twice its mass?
1.5 m/s2
This pocket watch is keeping perfect time. What is the angular speed ωof its minute hand in units of rad/s?
1.75*10^-3rad/s
A gardener is watering her garden from a hose. With the water pressure full blast holding the hose horizontally she can just reach a distance of 12 m, but needs to water an area up to 15 m away. By what fraction must she reduce the cross-sectional area of the hose, still keeping the hose horizontal, to be able to water this area?
1/5
A ball is thrown horizontally from the top of a 125 m tall tower with a speed of 20 m/s. What is its horizontal distance from the building when it strikes the ground?Let g = 10 m/s2.
100 m
A 500 N weight sits on the small piston of a hydraulic machine in equilibrium. The small piston has area 2.0 cm2. If the large piston has area 40 cm2, how much weight does the large piston support ?
10000 N
100 dB corresponds to what intensity, in W/m2?
10^-2 W/m^2
If the intensity of a 40 dB sound is increased to 80 dB, the intensity in W/m^2 increases by a factor of
10^4
Assume that a naked human body has a surface area of 1.5 m2and a surface temperature of 32oC. If the surroundings are at a temperature of 16oC, calculate the net rate of heat loss by the body due to radiation. Assume an emissivity of 1.
143 W
A Boeing 737 jet plane lands with a speed of 60 m/s (about 135 mi/h) and can decelerate on a wet runway at a maximum rate of 4 m/s2 as it comes to rest. What is the minimum time needed before the plane will come to rest?
15 s
A pure sound notesfrom a sources make the molecules of air at a location vibrate simple harmonically in accordance with the equationy1= 0.008 sin (302 π t ).What is the frequency of the sound wave?
151 Hz
A ball initially at rest is hit by a club. It is in contact with a club for 6.0*10-3seconds. Just after the club loses contact with the ball, the ball's velocity is 2.0 m/s. If the ball's mass is 50 g, what was the magnitude of the average net force acting on the ball while in contact with the club?
16.7 N
A crane lifts a 100 kg object to a height of 10 m in 5 s. What is its power output?
1960 W
Use g = 10 m/s2. Water descends from the top of a tall hydroelectric dam. Its gravitational potential energy is eventually converted into electric energy. How much gravitational potential energy is released when 1000 kg of water descend 200 m to the generators?
2 MJ
A fan rotating with an initial angular velocity of 1000 rev/min is switched off. In 2 seconds, the angular velocity decreases to 200 rev/min. Assuming the angular acceleration is constant, how many revolutions does the blade undergo during this time?
20
A person walks from A to B along a circular path of radius 10.00 m around 1/2 of the circle. What is the magnitude (in m) of the displacement vector?
20 m
A 10^4 N car is lifted by a manually operated hydraulic lift. The area of the shaft of the lift is 80 cm^2; the area of the piston that forces liquid into the system is 2 cm^2. What minimum force must be exerted on this piston to lift the car?
250 N
A ring shaped space station with a radius of 2 km is spinning, so that the speed of the rim is 100 m/s. A 50 kg woman sits on the inside of the rim. What is the magnitude of his apparent weight?
250 N
A block of wood of uniform density floats so that exactly ¼ of its volume is underwater. What is the density of the block?
250 kg/m3
A racecar has a speed of +90 m/s when the driver releases a drag parachute. If the parachute causes a uniform deceleration of -15 m/s2, how far will the car travel before it stops?
270 m
Your friends decide to play a prank on you and lock you in a room with two speakers making an incessant hum at 680 Hz. Which of the following locations would deafen the hum the most? (Take the speed of sound to be 340 m/s.)
3.00 m away from speaker A; 3.75 m away from speaker B
A standing wave is established on a 1.2 m long string fixed at both ends. The string vibrates in four segments when driven at 120 Hz. What is the fundamental frequency?
30 Hz
A force of magnitude 10 N compresses an ideal spring by 4 mm. How much force is needed to stretch the same spring by 12 mm?
30 N
A girl pulling a sled exerts a 20 N force horizontally for 40 s. How much power does she generate while moving the sled 60 m?
30 W
5 moles of a monatomic gas has its pressure increased from 105Pa to 3*105Pa. This process occurs at a constantvolumeof 0.1 m3. Determine the change in the internal energy of the gas.
30000 J
A pure sound notesfrom a sources make the molecules of air at a location vibrate with simple harmonic motion in accordance with the equationy1= 0.008 sin (604 π t).What is the frequency of the sound wave
302 Hz
A ball (mass 0.40 kg) is initially moving to the left at 40 m/s. After hitting the wall, the ball is moving to the right at 40 m/s. What is the impulse of the ball receives during its collision with the wall?
32 kg m/s to the right
Suppose you have a tube 0.25 m long with a speaker at one end and with the other end open. If you gradually increase the frequency of the speaker from zero at about what approximate frequency will you hear the first resonance?
350 Hz
Mercury has an unusually large surface tension γ= 0.465 N/m. Calculate the excess pressure inside a drop of mercury 5 mm in diameter.
372 Pa
A junior lifter lifts his 80 kg weight bar three times straight up off the ground a distance of 1.6 m before releasing it. How much work does he do?
3763 J
A stationary source S generates circular outgoing waves on a lake. The wave speed is 5.0 m/s and the crest-to-crest distance is 2.0 m. A person in a motorboat heads directly toward S at 3.0 m/s. To this person, the frequency of these waves is:
4 Hz.
A piece of clay with mass m = 0.01 kg collides with the floor at speed of 8 m/s and sticks. The collision takes 0.02 s. The magnitude of the average force the piece of clay experiences during the collision is
4 N
In the cyclic process on an ideal gas shown in the adjoining PV diagram, what is the net work done by the gas during the cycle?
4 PV
You walk in a given direction for 15 m during the first 4 seconds of a trip and then 25 m during the next 6 seconds. Your average speed is equal to
4 m/s.
A string of length 100 cm is held fixed at both ends and vibrates in a standing wave pattern. The first harmonic is shown. The wavelengths of the standing waves making up the pattern cannotbe
400 cm
A rock is kicked horizontally at 10 m/s off a cliff. The rock strikes the ground 30 m from the cliff as shown in the figure. What is the approximate height of the cliff H?
45 m
A 300 kg roller coaster cart starts from rest at a point 45 m above the bottom of a dip. Neglect friction. What will be its kinetic energy at the top of the next hill, which is 30 m above the bottom of the dip?Let g = 10 m/s2.
45000 J
Mercury has an unusually large surface tension γ = 0.465 N/m. Calculate the excess pressure inside a drop of mercury 4 mm in diameter.
465 Pa
When a tuning fork is sounded together with a 492 Hz tone, a beat frequency of 2 Hz is heard. Then a small piece of putty is struck to the tuning fork, and the tuning fork is again sounded along with the 492 Hz tone. The beat frequency decreases. What is the frequency of the tuning fork
494 Hz
Ice initially at -20 oC is to be turned into steam at 130 oC.To figure out how much heat is required, how many separate terms will there be
5
Which position versus time graph does NOT represent motion with constant acceleration?
5
We flip a fair coin 10 times. Define a macrostateto be the number of heads. Which macrostateis most likely to occur?
5 heads
A ball is dropped from the top of a 125 m tall tower. How long after it has been released does it hit the ground?Let g = 10 m/s2.
5 s
A fast pulsed laser emits a series of brief ps (10^-12s) pulses of light, one pulse per microsecond (10^-6s). If the average power of the laser is 50 W, what is the energy per pulse?
5*10^-5J
A fast pulsed laser emits a series of brief ps (10^-12s) pulses of light, one pulse per microsecond (10^-6s). If the energy per pulse is 5*10^-5J, what is the power of a pulse?
5*10^7W
An object rotates initially with a period of 1.0 s. It accelerates with constant angular acceleration for 10 s. Its final rotation period is 0.1 s. What was the magnitude of its angular acceleration?
5.65 rad/s2
A block of wood of uniform density floats so that exactly half of its volume is underwater. What is the density of the block?
500 kg/m3
Use g = 10 m/s2. A crane lifts a 200 kg object to a height of 20 m in 8 s. What is its power output?
5000 W
A CD spins at 5500 rpm (revolutions per minute). What is its angular speed in units of rad/s or s-1?
576
Beats are produced when two tuning forks, one of frequency 240 Hz and another of frequency 246 Hz are sounded together. The frequency of the beats is
6 Hz
A racecar has a speed of +90 m/s when the driver releases a drag parachute. If the parachute causes a uniform deceleration of -15 m/s2, how long will it take the racecar to stop?
6 s
A 50 kg woman balances on one heel of a high-heel shoe. If the heel is circular with radius 0.5 cm, what pressure does she exert on the floor?
6.2 MPa
A horizontal pipe, 10 cm in diameter, has a smooth reduction to a pipe 5 cm in diameter. If the pressure of the water in the larger pipe is 8.00*104 Pa and the pressure in the smaller pipe is 6.00*104 Pa, what is the flow speed of the water (in m/s) in the smaller pipe?
6.53 m/s
A 1200 kg car's speed changes from 0 to 20 m/s in 4 s. What is the average power of the car motor during this time period? Neglect friction.
60 kW
A 1400 kg car accelerates uniformly from rest to 60 mph in 6 s. Find the net force needed to produce this motion. 1 mile = 1609.344 m
6259 N
A train whistle is blown by the driver who hears the sound at 600 Hz. If the train is heading towards a station at 25.0 m/s, what will the whistle sound like to a waiting commuter? Take the speed of sound to be 340 m/s.
647 Hz
The magnitude of the force vector with (x, y) components (5 N, 5 N) is
7.1 N.
A non-constant force is applied to a 40 kg object over a distance of 20 m. (See diagram.) How much work does the force do?
80 J
An alarm clock makes a sound that has intensity 60 dB at a distance of 1 m. What is the sound intensity of 100 such clocks which are all 1 m away?
80 dB
The brake system in most cars makes use of a hydraulic system. This system consists of a fluid filled tube connected at each end to a piston. Assume that the piston attached to the brake pedal has a cross sectional area of one half a square inch and the piston attached to the brake pad has a cross section area of two square inches. When you apply a force of 20 pounds to the piston attached to the brake pedal, the force at the brake pad will be
80 pounds.
A 0.500 kg mass is attached to a spring of constant 150 N/m. A driving force F(t) = (12.0 N)cos(ωt) is applied to the mass, and the damping coefficient b is 6.00 Ns/m. What is the amplitude of the steady-state motion if ω is equal to half of the natural frequency ω0 of the system?
9.7 cm
A steel bridge is built in several segments, each 20 m long. The gap between segments is 2 cm at 18 oC.What is the maximum temperature that the bridge can manage before buckling?
95 oC
A particle is moving with constant speed along the circular path shown. Its velocity vector is shown at two different positions. What is the direction of the acceleration when the particle is at point X?
A
Three forces labeled A, B, C are applied to a rod which pivots on an axis through its center.Which force produces the torque with the largest magnitude about this axis?
A
Which system is in a state of stable equilibrium?
A marble in the bottom of a spherical bowl
Which of the following statements about vectors and scalars are TRUE?
A vector quantity has a direction and a scalar does not.
Fluid is flowing from left to right through the pipe. Points A and B are at the same height, but the cross-sectional areas of the pipe differ. Points B and C are at different heights, but the cross-sectional areas are the same. Rank the pressures at the three points, from highest to lowest.
A, B, C
We observe the harmonic motion of an object. Its position as a function of time shown in the graph below is given by x = 1* cos(π t), where x is measured in meter and t is measured in seconds. What are the amplitude (A), the period (T), and frequency (f) of the motion?
A: 1 m, T: 2 s, f: 0.5 Hz
Consider two carts, of masses m and 2m, at rest on an air track. You push on each cart for 3 s, exerting equal force Fnet on each.
After the push, the momentum of mass m is the same as the momentum of mass 2m.
If ∆ = 1 m and the speed of sound is 340 m/s, which statement is correct?
All of the above statements are correct.
Which sounds travel the fastest through air?
All sound travels at the same speed through air.
Consider three drinking glasses. All three have the same area base, and all three are filled to the same depth with water. Glass A is wider at the top than at the bottom, glass B is cylindrical and so holds less water than A. Glass C is narrower at the top than at the bottom, and so holds less water than B. Which glass has the greatest liquid pressure at the bottom?
All three have equal pressure at the bottom.
Three trajectories labeled A, B, and C are shown below. For which trajectory is the vertical velocity component at launch the greatest?
All three trajectories have the same initial vertical velocity component at launch.
Consider motion in one dimension along the x-axis.Which statement is TRUE?
An object that is slowing down while traveling in the negative x-direction always has a positive acceleration.
Arnie and Wimpy are playing tug-of-w a r. They have the same weight, but Arnie wins, pulling Wimpy into the mud puddle. Why did Arnie win?
Arnie exerted a greater magnitude force on the ground than Wimpy exerted on the ground.
A ball is fired by a cannon from the top of a cliff as shown in the figure below. Which of the path would the cannonball most closely follow?
B
Two pitchers are standing side by side, and simultaneously throw baseballs A and B. The balls follow the parabolic trajectories shown. Which of the following statements is true?
Ball B his the ground before ball A.
When I bake a sweet potato in the oven, I always put it on a thin sheet of aluminum foil. This is because sometimes the potato exudes a sugary juice that burns and makes a hard-to-clean-up mess if it drips on the bottom of the oven. When I'm ready to take the potato out of the hot (400o F) oven after an hour of cooking, I find I can pick up the aluminum foil with my bare hands without getting burned. Why?
Because the aluminum foil has a low specific heat and not much mass, so even at a high temperature it doesn't have a lot of thermal energy in it to burn me.
Two objects, A and B, have the same volume and are completely submerged in a liquid, although A is deeper than B.Which object, if either, experiences the greater buoyant force?
Both objects experience the same buoyant force.
You have heard the tried and true phrase "it is like running in to a brick wall". Now it is time to dig a little deeper and modify the phrase. Assume you are in a car driving and come in contact with this proverbial brick wall. Your car can do three things after the strike: it can go through, come to stop or bounce back. Select the option which will be the most dangerous to you assuming similar collision times.
Bouncing back
You need to loosen a very tight bolt. You have one wrench and you exert maximum force. Which configuration shown below gives you maximum chance of success?
C
A disk is spinning with angular velocity ωas shown. It begins to slow down. While it is slowing, what are the(i) directions of its angular velocity ω (ii) and its angular acceleration α?
C, D
Car 1 starts from rest along a straight highway with constant acceleration a = 1 m/s2. Car 2 passes car 1 with constant velocity of 120 km/hr. Which car is acted on by a larger net force?
Car 1
An object moves with constant speed in the clockwise direction along the circular path shown below. At the point indicated by the black dot, in which direction is the angular velocity vector ω pointing?
D
Consider the following five graphs (note the axes carefully). Which of these represent(s) one-dimensional motion at constant acceleration, including a = 0?
I, II, IV and V only.
You have watched one too many old cartoons and decide to drive around town with a giant spring that is 4 m long and attached to the front of your car. You decide to help a semi truck that is stuck and try to push them with your car. You take a running start, and when you contact the truck the spring in your car compresses 3 m. During which portion of the compression did you do the most work on the spring?
During the third meter.
In the figure, a 100 N weight is suspended from two spring scales, each of which has negligible weight. What is the reading of the scales?
Each scale will read 100 N
Why are good thermal conductors generally good electric conductors also?
Electron motion is responsible for determining both properties.
Modeling a meter stick as a forearm, compare the force FB that the biceps has to exert to keep the forearm horizontal to the weight of the forearm FW = mg. Let d = 10 cm and the distance from where the biceps muscle attached to the center of mass be d' = 40 cm.
FB = 5 mg
The velocity versus time graph to the right represents the motion of an object moving in one dimension along the x-axis. Between t = 12s and 15 s, the velocity of the object is negative.
False
Two flutists are tuning up. If the conductor hears the beat frequency increasing, are the two flute frequencies getting closer together or father apart?
Farther apart
A woman exerts a constant horizontal force pulling a box across a rough floor at a constant speed. What can you say about the work done by friction?
Friction does negative work
Referring to the graph below, which phase has the smallest specific heat capacity?
Gas
In soap box car races, the cars are boxes with wheels. They begin at rest at the top of a hill, and at the start of the race they all begin rolling down the hill. The soap box car that reaches the bottom of the hill first is the winner. You have entered a soap box car race where the rule is that all the wheels and cars must have equal mass. Since you have taken Physics, you know that it is worse to have wheels with spokes (where the mass is mostly on the rim) rather than solid wheels because
Given the same torque, the wheels with spokes have a higher rotational mass or moment of inertia and therefore will have a smaller angular acceleration.
Consider two masses, each of size 2m at the ends of a light rod of length L with the axis of rotation through the center of the rod. The rod is doubled in length and the masses are halved. Compare IA and IB.
IA < IB
Consider a rod of uniform density with an axis of rotation through its center and an identical rod with the axis of rotation through one end. Which has the larger moment of inertia about its axis of rotation?
IC< IE
Orange growers in Florida spray their trees with water when they expect a freeze. Why does this work?
If a mixed phase of water and ice is present, the temperature does not drop below 0 oC.
A "motion diagram" is shown. It is a series of snapshots of a bunny's position taken every 1.0 seconds. What is the direction of the acceleration vector if the bunny ismoving to the left?
In the positive x-direction
A simple pendulum of length L oscillates back and forth 10 times per second. By what factor do you have to change its length to make it oscillate back and forth only 5 times per second?
Increase the length by a factor of 4.
One mole of monatomic gas undergoes an adiabatic process (i.e. one where no heat enters or leaves the system). A pressure versus volume graph of the process is shown to the right. The initial and final volumes are given in the table below What are the initial and final temperatures
Initial T: 361 K; final T: 144 K
A metal body of mass 31.6 g occupies a volume of 4 cm3. Identify the metal.
Iron with density = 7.9 g/cm3
Consider the change a gas undergoes as it transitions from point c to point ain the PV diagram. What type of process is this?
Isobaric
A young girl wishes to select one of the frictionlessplayground slides illustrated above to give her the greatest possible speed when she reaches the bottom of the slide. Which of the slides illustrated in the diagram should she choose?
It does not matter, her speed would be the same for each.
When you fly a kite, there is a time when you must do positive work on the kite.
It is the time when you pull the kite in.
A gas, confined to an insulated cylinder, is compressed adiabatically(and reversibly) to half its original volume. Does the entropy of the gas increase, decrease, or remain unchanged during this process?
It remains unchanged
A stone is dropped from the roof of a single story building to the surface of the earth.
It speeds up because of an almost constant force of gravity acting upon it.
A car's speed changes from 20 mph to 60 mph. By what factor does its kinetic energy change?
It will increase by a factor of 9.
The fundamental dimensions of pressure are
M L^-1 T^-2
Consider the earth spinning from west to east on its axis. It is slowing down in its rotation due to friction with the air. Using the right hand rule, in what direction is the frictional torque?
N pole to S pole
Consider the earth spinning from west to east on its axis. It is slowing downin its rotation due to friction with the air. Using the right hand rule, in what direction is the frictional torque?
N pole to S pole
An ice-cube sits in a bath of water. The water, the ice and the surrounding air are all at 0 oC.Does heat enter the ice cube?
No
Is it possible to cool down a well insulated room on a hot summer day by leaving the refrigerator door open, and using the refrigerator as an air conditioner?
No
When a car is at rest, its horn emits a sound wave of wavelength 0.55 m. A person standing in the middle of the street hears the horn with a frequency of 560 Hz. If the speed of sound is 330 m/s, should the person jump out of the way?
No
Your friend asks you to stand perfectly still holding up a weight bar with weights while he takes a picture. Are you doing work during this time?
No
Velocity versus time graphs are shown for 4 objects, A, B, C, and D. Which statement is true?
None of the above
A 50 N force and a 100 N force both act on the same object. What is the net force (total force) acting on the object?
Not enough information is given.
Two objects have masses m1and m2, respectively. If m2= 4m1, and both have the same kinetic energy, which has more momentum (magnitude)?
Object 2 with mass m2
Two moving objects have masses m1 and m2, respectively. If m2 = 4m1, and both have the same kinetic energy, which has more momentum?
Object 2 with mass m2.
A ball is thrown straight upward. It rises in the air and then falls back to earth. Neglect friction.
On the way up, kinetic energy is converted to potential energy.
Which of the following statements about distance and/or displacement are TRUE? (1) Distance is a vector quantity and displacement is a scalar quantity. (2) If a person walks in a straight line and never changes direction, then the distance and the magnitude of the displacement are exactly the same. (3) The diagram below depicts the path of a person walking from position A to B back to C to and then to D. The distance traveled is 90 yds. (4) For the same diagram below, the displacement of the person walking from A to B to C to D is 50 yds.
Only statements 2 and 3 are true.
The positions of two blocks at successive 0.20-second time intervals are represented by the numbered squares in the figure below. The blocks are moving towards the right. Are the blocks accelerating?
Only the upper block is accelerating.
Which of the following statements is false?
Plaque deposit on an artery or arteriole wall causes an increase in local blood pressure and can lead to bursting of that vessel.
In the constellation Orion, you can easily observe the difference between the reddish looking star Betelgeuse and the bluish looking star Rigel. Which of the two has the hotter surface temperature?
Rigel
Consider a rod of uniform density with an axis of rotation through its center and an identical rod with the axis of rotation through one end. Which has the larger moment of inertia about its axis of rotation?
Rod B with the axis through one end.
A rock is thrown straight up from the surface of the Earth. Which one of the following statements describes the energy transformation of the rock as it rises? Neglect air resistance.
The KE decreases and the PE increases
The positions of two blocks at successive 0.20-second time intervals are represented by the numbered squares in the figure below. The blocks are moving towards the right. The accelerations of the blocks are related as follows:
The acceleration of a equals the acceleration of b. Both accelerations are zero.
On a humid summer day, perspiration does not cool you off much. Why?
The air is almost saturated with water vapor and there is almost no net evaporation.
A block and a rod are joined together. Each object is of uniform density. The center of mass of the combined object is at the position shown by the "X." Which has the greater mass, the block or the rod?
The block has the greater mass.
Suppose you work in the E.R. and a choking patient comes in with their trachea obstructed. The diameteris 1/3 of what it was before the obstruction. You manage to correct the problem and send them on their way safely, explaining that such obstructions are particularly dangerous because
The blocked airway passes only 1/81 the regular amount of air.
Determine the character of the collision. The masses of the blocks, and the velocities before and after are given.
The collision is not possible because momentum is not conserved.
An ideal, non-compressible fluid is used in the system of pipes shown below. The cross sectional area of pipe 1 is 4 m2, that of pipe 2 is 3 m2, and that of pipe 3 is 2 m2. The fluid enters pipe 1 at 2 m/s, and leaves pipe 2 at 3 m/s. What is the speed of the fluid in pipe 3 and in which direction does it flow?
The fluid leaves pipe 3 (downward) with speed 0.5 m/s.
A mass M, attached to a piece of string OM, is whirled round over a person's head in a horizontal circle. At the position shown in the diagram below, the string suddenly breaks. In which direction does the mass M move horizontally after the string breaks?
The mass M moves in the direction III.
A chair has a wooden seat but metal legs. The chair legs feel colder to the touch than does the seat. Why?
The metal has a higher thermal conductivity than the wood
A force of 20 N in the positive x-direction accelerates an object with acceleration a = 2 m/s2. When the object is moving with velocity v = 10 m/s, an additional force of 10 N in the negative x-direction is applied.Which statement is true?
The object now accelerates with acceleration a = 1 m/s2 in the positive x-direction.
Blood flows through a section of a horizontal artery that is partially blocked by a deposit along the artery wall. A hemoglobin molecule moves from the wider region into the narrower region. What happens to the pressure acting on the molecule as it moves from the wider into the narrower region?
The pressure decreases
Water is flowing smoothly through the pipe shown in the diagram.
The pressure is lowest in section B
A 10 kg and a 4 kg mass are acted on by the same magnitude net force (which remains constant) for the same period of time. Both masses are at rest before the force is applied. After this time, the 10 kg mass moves with a speed v1 and the 4 kg mass moves with a speed v2. Which of the following is true?
The ratio v1/v2 is equal to 2/5.
Both the disk and the ring have the same mass, and the same radius. Which has the larger moment of inertia I about the center?
The ring
Two bubbles are connected by a hollow tube plus a valve. What will happen once the valve between the two is opened?
The small bubble will drain into the big bubble.
In your dorm room you watch the Vols play in an out-of -town game. It is a cliff hangers and the winner will be determined in the last few seconds of play. Everybody is taking their bathroom break right after the game ends. As the toilets flush and hands are washed, the faucet pressure is noticeably reduced, even though the supply pipe to the rooms can carry all the water needed. Why?
The water has to speed up in the supply pipe and therefore the pressure drops in the pipe.
A woman pulls a crate up a rough, inclined plane at constant speed. Which one of the following statements concerning this situation is false?
The work done on the object by gravity is zero.
The diagram below depicts two pucks on a frictionless table. Puck II is four times as massive as puck I. Starting from rest, the pucks are pushed across the table from the start to the finish line by two equalforces.Which puck will have the greater kinetic energy upon reaching the finish line?
They both have the same kinetic energy.
A pocket watch and Big Ben are both keeping perfect time. Which minute hand has the larger angular speed ω?
They both have the same ω.
How will the wavelengths of the harmonics of an open tube compare with those of a string of the same length L?
They will be the same
Why can't you get all the dust off your car by just squirting water from a hose onto it? Why can't you simply remove dust just by blowing across a surface? Why does dust cling to a fast rotating fan? How can a leaf stay on a car moving at high speed?
This is a consequence of the formation of stationary boundary layer.
An ice cube is placed in a cup containing some liquid water. The water and ice exchange energy with each other but not with the outside world.Consider the following possibility: After awhile, we find that the water has increased in temperature and ice has gotten colder.Which statement is correct?
This process can satisfy the 1st law, but still does not happen in nature
Why does heat, of itself, not flow from a cold to a hot object, if it is allowed by Newton's laws?
This would require a large departure from equilibrium, which is extremely unlikely
It is possible for heat to flow across vacuum.
True
It is possible to change the temperature of a system when the system is insulated from its surroundings, so that no heat can flow into and out of the system.
True
When a car drives down a street full of fallen leaves, the leaves swirl around behind the car. What kind of flow is present behind the car?
Turbulent flow
The graph shows the net force acting on an astronaut during a rocket launch into a stable orbit. During which time interval was the acceleration of the rocket the greatest?
U-V
A boat floating in a lake contains a block of volume V0. The density of the block is 5000 kg/m3. If the block is thrown overboard, the volume of the water displaced by the block is
V0.
We flip a fair coin 10 times. Define a macrostateto be the number of heads. Define each microstate as a a particular sequence of heads and tails. Some microstates for coin flips are listed below. "H" stands for heads and "T" stands for tails. Rank the microstatesfrom most likely to least likely to occur
VI) = III) = II) = I)
Your dryer is broken, so you have to hang your wet clothes from the washing machine outside to dry. Under which conditions would your clothes dry fastest?
When it is 75°F with 50% relative humidity.
You are cutting wood with a hand saw. You have to push the saw away from you as it moves away from you and pull it towards you as it moves towards you. When are you doing positive work on the saw?
When pushing it away from you and when pulling it towards you.
You operate a 120 W light bulb for 1 hour. How much energy did you use? (1 W = 1 J/s)
You operate a 120 W light bulb for 1 hour. How much energy did you use? (1 W = 1 J/s)
Suppose you work in the E.R. and a choking patient comes in with their trachea half obstructed. (The diameteris half of what it was before the obstruction.) You manage to correct the problem and send them on their way safely, explaining that such obstructions are particularly dangerous because
a half - blocked airway passes only1/16 the regular amount of air.
As a sound source moving with constant velocity approaches and then moves past a stationary observer, the observer will hear
a sudden drop in pitch
Sound waves
are longitudinal waves.
Water with air bubbles flows through a pipe that becomes narrower. Compared to the wider region, the bubbles in the narrow region are
bigger
In an experiment water rose by capillary attraction through two columns of soils, one with coarse grains (column 1) and the other with fine gains (column 2).In which column did the water rise to greater height?
column 2
An object moves from one point in space to another. After it arrives at its destination, the magnitude of its displacement vector is __________________________________ (insert here)the distance it traveled. 1.either greater than or equal to 2.always greater than3.either smaller than or equal to4.always smaller thanHint: Does the object have to move along a straight line?
either smaller than or equal to
A rock is thrown from the roof of a tall building.While it is falling towards the ground, the force of gravity acting on it is
equal to its weight.
Two objects are traveling around different circular orbits with constant speed. They both have the same centripetal acceleration, but object A is traveling twice as fast as object B. The orbit radius for object A is
four times the orbit for object B.
Suppose you are standing on a bathroom scale when you are flying in a jet airplane. For a moment the scale reads more than your actual weight. During that moment, the scale is exerting an upward force on you that is
greater than your weight.
Two fluids have the same contact angle with glass. The density of fluid 1 is 1.2 times the density of fluid 2. (ρ1= 1.2 ρ2)The surface tension of fluid 1 is twice that of fluid 2. (γ1= 2γ2)Find the ratio h1/h2of the heights to which a liquid will rise through capillary action in the same capillary tube.
h1/h2 = 1.67
A woman exerts a constant horizontal force on a large box. As a result, the box moves across a horizontal floor at a constant speed v0. The constant horizontal force supplied by the woman
has the same magnitude as the total force which resists the motion of the box.
During a football game the ball is kicked and it travels across the field. If the ball is kicked away from its center of mass it will
have translational and rotational motion.
A heat engine extracts usable work by permitting
heat to flow from a hotter object to a colder object.
A man, with his arms at his sides, is spinning on a light frictionless turntable. When he extends his arms
his angular momentum remains the same.
Flowing honey is less likely to become turbulent than flowing water because
honey's large viscosity favors laminar flow
You paddle in a Kayak across a calm mountain lake. Each time you pull the paddle backward through the water, from the front of the boat to its rear, the water exerts a force on the paddle that is
in the forward direction, towards the front of the boat.
Consider a block of wood floating on water. If you push down on the top of the block untilit is completely submerged, the buoyant force on it
increases
When the kinetic energy of a moving object increases by a factor of 16, the magnitude of its momentum
increases by a factor of 4.
Blood is called a complex fluid because
its viscosity depends on the velocity of the flow,
The _______ the temperature difference between hot and cold, the larger the fraction of heat you can divert and transform into __________.
larger; work
In the absence of air resistance, a ball of mass m is tossed upward to reach a height of 20 m. At the 15 m position, 3/4 of the way up, the net force on the ball is
mg
A person sips a drink through a straw. At which of the following three positions is the pressure lowest? I. Inside the person's mouth II. At the surface of the drink III. At the bottom of the drink
only at position I
People fighting forest fires carry emergency tents that have shiny aluminum outer surfaces. If there is trouble, a fire fighter can lie under the tent to block the heat from burning trees overhead. The tent helps becaus
radiation carries heat downward toward the fire fighter and the aluminum tent reflects most of that radiation
A simple pendulum consists of a point mass m suspended by a massless, unstretchablestring of length L. If the mass is doubled while the length of the string remains the same, the period of the pendulum
remains unchanged
A refrigerator
removes heat from a cold region and delivers the more heat to a hotter region
One kilogram of iron (density ~7.8 gm/cm3) and 1 kilogram of aluminum (density ~2.7 gm/cm3) are dropped into a pool. Which is acted on by the largest buoyant force?
the aluminum
Some children are riding on the outside edge of a merry-go-round. Ignore friction in the rotation of the merry-go-round. Consider the "system" of the children plus the merry-go-round. At the same time, the children all move towards the center of the merry-go-round. When they do this
the angular momentum of the system stays constant.
Your hands push on a heavy box to slide it across the floor. The other force of the action/reaction pair is
the box pushing backward against your hands
You can balance a broom on your hand if you're careful. To do this trick well, you must look at
the broom's center of gravity.
When you sit facing a campfire outdoors, your face feels quite warm because
the campfire is radiating heat towards your skin.
It is correct to say that impulse is equal to
the change in momentum
As I apply the brakes in my car, books on the passenger seat suddenly fly forward. That is most likely because
the decelerating car is not an inertial reference frame.
The longer the wavelength of a sound wave
the lower is its pitch.
Consider a car at rest. We can conclude that the downward gravitational force Earth exerts on the car and the upward contact force the surface of Earth exerts on the car are equal in magnitude and opposite in direction because
the net force on the car is zero.
A baseball bat with uniform density is cut at the location of its center of mass as shown in the figure. The piece with the smaller mass after the cut is
the piece on the left.
Suppose you have an aquarium. You have a solid plastic decoration and a rock of about the same volume but the rock has twice the mass. Both are totally submerged in the water. The buoyant force on the plastic object is about
the same as that on the rock
A sinusoidal force with a given amplitude is applied to an oscillator. To maintain the largest amplitude oscillation, the frequency of the applied force should be
the same as the natural frequency of the oscillator.
A car traveling at 100 km/hr strikes an unfortunate bug and splatters it. The magnitude of the force of impact is
the same for both
Standing waves are produced by periodic waves of
the same frequency, amplitude, and wavelength traveling in opposite directions
Compared to a gear tooth on the rear sprocket (on the left, of small radius) of a bicycle, a gear tooth on the front sprocket (on the right, of large radius) has
the same linear speed and a slower angular speed.
Two objects with different masses collide and stick to each other. Compared to before the collision, the system of two objects after the collision has
the same total momentum but less total kinetic energy
The speed of sound waves having a frequency of 256 Hz compared to the speed of a sound wave having a frequency of 512 Hz is
the same.
A pitcher contains 0.50 kg of liquid water and 0.50 kg of ice at 0°C. You let heat flow into the pitcher until there is 0.75 kg of liquid water and 0.25 kg of ice. During this process
the temperature of the ice-water mixture remains the same.
Two blocks, one sitting on a table and the other heavier one hanging over its edge, are connected by a light string as shown in the figure. Which force makes the block on the table move, the tension in the string or the weight of the hanging block?
the tension
An elevator is being lifted up an elevator shaft at a constant speed by a steel cable as shown in the figure above. All frictional effects are negligible. In this situation, forces on the elevator are such that
the upward force by the cable is equal to the downward force of gravity.
Some engineers have suggested that we can simulate gravity in outer space by having a circular rotating space station where persons feel an outward-directed fictitious force due to the rotation of the station. The reason they feel such a force is because
they are accelerating toward the center of the space station and the walls of the space station provide the centripetal force, which they experience as an apparent weight.
A scuba diver descends to a depth of 20 m. At that depth, the pressure is approximately
three times atmospheric pressure.
A heavy box sits in the back of a pickup truck. The truck and the box are accelerating towards the left. What is the direction of the frictional force on the box?
towards the left
If you double the wavelength λ of a wave on a string under fixed tension, what happens to the wave speed v and the wave frequency f?
v is unchanged and f is halved.
Sound does not pass through
vacuum.
Consider two specimens of ideal gas at the same temperature.The molecules in specimen #1 have greater molar mass than the molecules in specimen #2. How do the root-mean-square or RMS speeds, vrms= √<v2>, of molecules and the average translational kinetic energy per molecule, <KE> = ½m<v2>, compare in the two specimens?
vrmsis greater in specimen #2; <KE>is the same in both specimens.
A woman exerts a constant horizontal force on a large box. As a result, the box moves across a horizontal floor at a constant speed v0. If the woman doubles the constant horizontal force that she exerts on the box, and the force resisting the motion of the box does not change, the box then moves
with constantly increasing speed.
Position, velocity and acceleration of an oscillating mass on a spring are shown as a function of time.What is the frequency of the oscillations?
~0.4/s
Position, velocity and acceleration of an oscillating mass on a spring are shown as a function of time. If the mass is 0.2 kg, what is the spring constant in N/m?
~1.2
You hear the sound of the ring of a distant cannon 5 seconds after seeing the flash. How far are you from the cannon
~1700 m
Measure the frequency or period of a 0.1 kgmass oscillating on a spring.What is the spring constant of this spring?
~3 N/m
An ideal gas in a closed container with a piston lid is taken from thermodynamic state, 1, to a new thermodynamic state, 2, by an isothermalpath as shown below in the P-V plane.Let ΔU be the internal energy changeduring this process, ΔQ be the heat transferred into the gas, and ΔWbe the work done by the gas.
ΔW is positive, ΔQ is positive and ΔU = 0
A student sees the following question on an exam:A flywheel with mass 120 kg and radius 0.6 m, starting at rest, has an angular acceleration of 0.1 rad/s2. How many revolutions has the wheel undergone after 10 s?Which single formula might the student use to answerthe question?
θf = θi+ ωi(tf- ti)+ ½ α(tf- ti)^2
A small wheel and a large wheel are connected by a belt. The small wheel is turned at a constant angular speed ωs. How does the angular speed of the large wheelωLcompare to that of the small wheel?
ωs>ωL