PHYS 221 UTK Final Elston
What is the approximate period of the sound waves shown here? (The speed of sound in air is ~340 m/s.)
0.0037 s
A point source of sound waves emits a disturbance with a power of 50 W = 50 J/s into a surrounding homogeneous medium. What is the intensity of the sound at a distance of 10 m from the source?
0.04 W/m2
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
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
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
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
The temperature on a nice summer day is 84 oF. What is the temperature on the absolute (Kelvin) temperature scale?
302 K
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
A sine wave and a square wave cannot have the same
tone quality
Sound does not pass through
vacuum
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.
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 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.
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 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?
½mv2 + ½ky2 + mg(L - y) = mgL
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
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
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 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
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.
Is it possible to have motion in the absence of a net force?
Yes
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.
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.
In the figure below, two point sources S1 and S2, which are in phase, emit identical sound waves of wavelength 2.0 m.If L1 = 39 m and L2 = 36 m, what type of interference occurs at point P?
destructive interference
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
In a mixture of hydrogen, oxygen, and nitrogen gases at a given temperature, the molecules having the greatest average speed are those of
hydrogen
In any process, the maximum amount of mechanical energy that can be converted into thermal energy
is 100%
A string is clamped at both ends and then plucked so that it vibrates in a standing mode between two extreme positions a and c. Let upward motion correspond to positive velocities. When the string is in position b, the instantaneous velocity of points along the string
is zero, positive, or negative, depending on the position along the string.
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
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
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
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.
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.
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.
(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 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
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 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.
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 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
The fundamental dimensions of pressure are
M L-1 T-2
Sound waves
are longitudinal waves
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
A hypothetical engine operates in a cycle taking in 10,000 J from a hot reservoir and 5000 J from a cold reservoir. In the cycle it performs 15,000 J of work. Such an engine
obeys the first law but violates the second law of thermodynamics.
Rockets receive their forward propulsion through
pushing against the exhaust.
The longer the wavelength of a sound wave
the lower is its pitch
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
An ideal reversible engine takes in 5 kJ of energy via heat transferred in from a 500 K burner and exhausts heat at 300 K during each closed cycle in the PV plane. The amount of heat exhausted at 300 K each cycle is
3 kJ
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
Pressure vs. volume graphs for a certain gas undergoing five different cyclic processes are shown to the right. During which cycle does the gas do the greatest positive work?
IV
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 (3) and (4) 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.
(a)
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
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
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
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/s2
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
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
A 0.5 kg mass oscillates about the equilibrium position on a vertical spring with spring constant 10 N/m. Where is its equilibrium position measured from the unstretched spring position (without the hanging mass)?
0.49 m
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?
0.72 s
The temperature in a furnace used to melt Aluminum is 660 oC. What is the average kinetic energy of the air molecules in the furnace?
1.93*10-20 J
A vector of magnitude 20 is added to a vector of magnitude 25. The magnitude of this sum might be
12
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
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
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 box with a total surface area of 1.2 m2 and a wall thickness of 4 cm is made of an insulating material. A 10 W electric heater inside the box maintains the inside temperature at 15 oC above the outside temperature. What is the thermal conductivity of the insulating material in units of kcal/(s oC m)?
5.3 x 10-6
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 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
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
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 ω0of the system?
9.7 cm
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
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
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
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
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.
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
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.
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 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.
In an inertial frame, an object cannot remain at rest unless which of the following holds?
The net force acting on it is zero
Which of the statements below is wrong?
The net force acting on the pendulum bob is F = -mgsinθ. The period increases with amplitude because this force increases faster than harmonic restoring force F= -mgθ.
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
Two carts collide on a nearly frictionless track. (See lab 6, experiment 3.)Cart 1 has mass m1 = 2 kg and cart 2 has mass m2 = 1 kg. For the velocities of the carts before and after the collision we obtain the following data. v1i = 6 cm/s and v2i = -12 cm/s. v1f = -3.599 cm/s and v2f = 7.2 cm/s. To within 1% uncertainty, which of the statements below are true?
The total momentum of the two carts is conserved.
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.
Why do elastic balls bounce so well?
They store energy through compression, like a spring.
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.
The volume of a gaseous sample is increased from V1to 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.
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.
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
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