Physics 207 Exam 2
Two masses, M and 5M , are at rest on a horizontal frictionless table, with a compressed spring of negligible mass between them. The spring is then allowed to expand and accelerate the two masses. (A) The two masses receive equal magnitudes of momentum. (B) The larger mass gains a larger magnitude of momentum than the lighter mass. (C) The smaller mass gains a larger magnitude of momentum than the heavier mass. (D) The two masses receive equal amounts of kinetic energy from the spring. (E) The larger mass gains more kinetic energy than the lighter mass. (F) The smaller mass gains more kinetic energy than the larger mass.
(A) The two masses receive equal magnitudes of momentum. (F) The smaller mass gains more kinetic energy than the larger mass.
There is a 500 N block initially at rest on a smooth horizontal surface. You apply a constant 500 N force at an angle 45◦ above the horizontal. You apply this force for a displacement of 10 m and then the block encounters a uniformly rough patch. It slides a bit further and then stops. The coefficients of static and sliding friction are 1.00 and 0.50 respectively. How far, from the point at which you stopped applying the force, does the block slide? (A) 7.0 m (B) 10 m (C) 14 m (D) 20 m (E) 28 m
(C) 14 m
Two objects are moving at equal speed along a level, frictionless surface. The second object has twice the mass of the first object. They both slide up the same frictionless incline plane. Which object rises to a greater height?
The two objects rise to the same height.
A jar is completely filled with water, and then it is sealed with a lid. If you push down on the lid with a pressure of 1000 Pa, what happens to the water pressure at the bottom of the jar?
The water pressure at the bottom of the jar will increase by 1000 Pa.
Water flows through a horizontal pipe. The diameter of the pipe at point B is larger than the diameter of the pipe at point A. Where is the water pressure the greatest?
The water pressure is the greatest at point B.
A graph depicts force versus position. What represents the work done by the force over the given displacement?
The work done is equal to the area under the curve. Submit
An astronaut in deep space, far from Earth, wants to measure the mass of a large wrench. Which one of the following techniques will work? (A) Let it slide down an incline and measure its acceleration. (B) Put it on a scale and weigh it. (C) Measure the radial force needed to keep it moving in a circle with a known radius and speed. (D) Turn on the rocket engines so the rocket is accelerating at a know rate and measure the backward acceleration of the free floating wrench relative to the rocket. (E) None of these methods will work.
(C) Measure the radial force needed to keep it moving in a circle with a known radius and speed.
Suppose the experiment shown in the video is repeated with objects having masses of 1/2m, m, and 2m, dropped from heights of h and 2h. Rank the following objects from the lowest kinetic energy at the point of impact with the box to the highest kinetic energy at the point of impact. If two objects have the same kinetic energy, place one on top of the other. 2m, 2h; m, 2h; 2m, h; 2m, 2h; 0.5m, 2h; m, h; 0.5m, h
(highest) 2m, 2h; m, 2h = 2m, h; 0.5m, 2h = m, m, h; 0.5m, h (lowest)
The amount of kinetic energy an object has depends on its mass and its speed. Rank the following sets of oranges and cantaloupes from least kinetic energy to greatest kinetic energy. If two sets have the same amount of kinetic energy, place one on top of the other. 4m, 1/4v; 2m, 1/2v; m, v; 4m, v; 4m, v
(least) 4m, 1/4v; 2m, 1/2v; m, v; 4m, v = 4m, v (most)
For an elastic collision, which of the following statements are true?
- Kinetic energy is conserved. - Momentum is conserved.
In the opening scenes of the prelecture video, we outlined some of the key properties of momentum. Which of the following statements are consistent with these properties?
- Momentum is a vector quantity. - An object's momentum is equal to the product of its mass and its velocity.
Bumper cars A and B undergo a collision during which the momentum of the combined system is conserved. Which equation(s) correctly states the principle of conservation of momentum?
- Pai + Pbi = Paf + pbf - deltaPa + deltaPb = 0
When a constant force acts on an object, what does the object's change in momentum depend upon?
- The change in momentum depends upon the magnitude of the force. - The change in momentum depends upon the change in the velocity of the object. - The change in momentum depends upon the mass of the object. - The change in momentum depends upon the time interval during which the force acts.
On what does the magnitude of an applied torque depend?
- The distance between the point of force application and the axis of rotation of the object. - The magnitude of the force. - The orientation of the force.
Which of the following statements are true? - The gravitational force between two objects is proportional to the square of the distance between the two objects. - The gravitational force between two objects is inversely proportional to the distance between the two objects. - The gravitational force between two objects is inversely proportional to the square of the distance between the two objects. - The gravitational force between two objects is proportional to the product of the masses of the two objects. - The gravitational force between two objects is proportional to the distance between the two objects. - The gravitational force between two objects is inversely proportional to the product of the masses of the two objects.
- The gravitational force between two objects is inversely proportional to the square of the distance between the two objects. - The gravitational force between two objects is proportional to the product of the masses of the two objects.
A girl moves quickly to the center of a spinning merry-go-round, traveling along the radius of the merry-go-round. Which of the following statements are true?
- The moment of inertia of the system decreases. - The angular speed of the system increases.
Which of the following statements are true? - The Sun is located at the center of the of the planets' circular orbits. - The path of the planets around the Sun is elliptical in shape. - The path of the planets around the Sun is circular in shape. - The Sun is located at one of the foci of the planets' elliptical orbits.
- The path of the planets around the Sun is elliptical in shape. - The Sun is located at one of the foci of the planets' elliptical orbits.
If a metal wire is 4m4m long and a force of 5000N5000N causes it to stretch by 1mm1mm, what is the strain?
0.00025
A contestant in a game show spins a stationary wheel with radius of 0.50 m so that it has a constant angular acceleration of 0.40 rad/s^2. What is the tangential acceleration of a point on the edge of the wheel?
0.20m/s^2
Suppose that we attach Velcro to the non-magnetic ends of the two carts in the video and remove the mass bars, so that both carts have the same mass. We repeat the experiment shown in the video, and the carts stick together after they collide. If the launch cart travels at a speed v0, then how fast will the combined two-cart system travel after the collision?
0.5v0
A turntable begins to rotate from rest with a constant angular acceleration. If a point on the edge of the turntable travels 9 radians during a 3 second time period, the angular acceleration of the turntable is:
2.0s^-2
On a snowy day, Max (mass = 15 kg) pulls his little sister Maya in a sled (combined mass = 20 kg) through the slippery snow. Max pulls on the sled with 12 N of force, directed at an angle of 15° above the ground. When he comes to a recently plowed section of road, he continues to pull the sled with the same force across the road while the road exerts a frictional force of 4 N on sled. If the sled's speed is 1.5 m/s as Max pulls it onto the road, what is the sled's speed after Max pulls it 5 m across the road?
2.5 m/s
a thin wire that is 2.5 meters long is measured to be 2.505 meters long under tensile stress. Its Young's modulus is 800 N/m^2. The tensile stress is now tripled and the wire remeasured. The wires length is now:
2.515m
A perfect Hooke's Law spring with a spring constant of 200 N/m has an equilibrium length of 0.50 m. The spring starts from a initial length of 1.00 m (stretched) and you now stretch the spring further so that it is 2.0 m long. How much work did you do? (A) 50 J (B) 150 J (C) 200 J (D) 300 J (E) 400 J
200J
A 3.6kg chihuahua charges at a speed of 3.3m/s. What is the magnitude of the average force needed to bring the chihuahua to a stop in 0.50s?
24 N
On a snowy day, Max (mass = 15 kg) pulls his little sister Maya in a sled (combined mass = 20 kg) through the slippery snow. When Max pulls on the sled with 12 N of force, directed at an angle of 15° above the ground, how much work does Max do on the sled as he pulls his sister 25 m in the snow?
290 J
Two children want to balance horizontally on a seesaw. The first child is sitting one meter to the left of the pivot point located at the center of mass of the seesaw. The second child has one-half the mass of the first child. Where should the second child sit to balance the seesaw?
2m to the right of the pivot
On a snowy day, Max (mass = 15 kg) pulls his little sister Maya in a sled (combined mass = 20 kg) through the slippery snow. Max pulls on the sled with 12 N of force, directed at an angle of 15° above the ground. When he comes to a recently plowed section of road, he continues to pull the sled with the same force across the road while the road exerts a frictional force of 4 N on sled. What is the net work done on the sled while Max pulls it 5 m across the road?
38 J
A spring has an equilibrium length of d. If I start with an initial length of 2d and increase the length to 3d then by what factor (Usf / Usi) does the potential energy change? 1.5 2. 2.25 4 9
4
A 1700kg rhino charges at a speed of 50.0km/h. What is the magnitude of the average force needed to bring the rhino to a stop in 0.50s?
4.7×10^4 N
A metal bar is elongated by 2mm when put under a certain amount of tension. How much will it be elongated if the tension is doubled?
4mm
A person of mass 70kg runs up a flight of stairs with a vertical height of 5m. If the trips takes 7s to complete, the person's power is
500W
Shown below is a graph of a force applied to a small object as a function of time. If the object has a mass of 5.0kg and is at rest at t=0s, how fast is the object moving at t=4.0s?
7.2 m/s
A traveler pulls on a suitcase strap at an angle 36° above the horizontal. If 908 J of work are done by the strap while moving the suitcase a horizontal distance of 15 m, what is the tension in the strap ? 92 N 61 N 75 N 85 N
75 N
Cheryl is riding on the edge of a merry-go-round, 2m from the center, which is rotating with an increasing angular speed. Cheryl's tangential acceleration is 3.0m/s2. At the instant that Cheryl's linear speed is 4.0m/s, what is Cheryl's total acceleration?
8.5 m/s^2
Consider a uniform solid sphere of radius R and mass M rolling without slipping. Which form of its kinetic energy is larger, translational or rotational?
A) Its translational kinetic energy is larger than its rotational kinetic energy.
Consider a uniform solid sphere of radius R and mass M rolling without slipping. Which form of its kinetic energy is larger, translational or rotational? A) Its translational kinetic energy is larger than its rotational kinetic energy. B) Its rotational kinetic energy is larger than its translational kinetic energy. C) Both forms of energy are equal. D) You need to know the speed of the sphere to tell.
A) Its translational kinetic energy is larger than its rotational kinetic energy.
You have three identical balls, and three beakers containing different liquids. Each ball has a density of 600 kg/m3 . You place one ball in each beaker. In beaker A the ball floats with 50% of its volume submerged. In beaker B the ball floats with 25% of its volume submerged. In beaker C the ball sinks to the bottom. Rank these liquids based upon the buoyant force felt by the ball, from largest to smallest.
A=B>C
Object A has a mass m and a speed v, object B has a mass m/2 and a speed 4v, and object C has a mass 3m and a speed v/3. Rank the objects according to the magnitude of their momentum. Rank from smallest to largest.
A=C < B
Bernoulli's principle can be used to explain the lift force on an airplane wing. How must an airplane's wing be designed to ensure that Bernoulli's principle is applicable?
Airplane wings must be designed to ensure that air molecules move more rapidly over the top surface of the wing, creating a region of lower pressure.
In a collision between two objects having unequal masses, how does magnitude of the impulse imparted to the lighter object by the heavier one compare with the magnitude of the impulse imparted to the heavier object by the lighter one?
Both objects receive the same impulse.
A girl and a boy are riding on a merry-go-round that is turning at a constant rate. The girl is near the outer edge, and the boy is closer to the center. Who has greater tangential acceleration?
Both the girl and the boy have zero tangential acceleration.
Which of the following shapes would have the slowest acceleration down a ramp? A) a solid sphere B) a solid cylinder C) a hollow cylinder D) a hollow sphere
C) a hollow cylinder
A solid bowling ball rolls down a ramp. Which of the following forces exerts a torque on the bowling ball about its center? A. the weight of the ball B. the normal force exerted by the ramp C. the friction force exerted by the ramp D. more than one of the above E. depends on whether the ball rolls without slipping
C. the friction force exerted by the ramp
A heavy boy and a lightweight girl are balanced on a massless seesaw. If they both move forward so that they are one-half their original distance from the pivot point, what will happen to the seesaw? Assume that both people are small enough compared to the length of the seesaw to be thought of as point masses. A) It is impossible to say without knowing the masses. B) It is impossible to say without knowing the distances. C) The side the boy is sitting on will tilt downward. D) Nothing will happen; the seesaw will still be balanced. E) The side the girl is sitting on will tilt downward.
D) Nothing will happen; the seesaw will still be balanced.
What is the relationship between mass, volume, and density?
Density is proportional to mass and inversely proportional to volume.
Now, consider the collision between two happy balls described in Part A. How much of the balls' kinetic energy is dissipated?
None of it
Two objects with different masses collide with and bounce off each other. Compared to before the collision, the system of two objects after the collision has
Not enough information is given to decide. (we do not know the type of collision)
The video shows an animated billiards experiment in which a cue ball strikes a glued-in-place eight-ball. Which of the following explains why the momentum of the eight-ball is conserved?
The "glue force" cancels the collision force.
While goofing off at the ice skating rink, a student takes off her shoes and places each of them on the ice. Her friend, a hockey player, then shoots a hockey puck at each shoe. The first puck immediately comes to rest after it collides with the left shoe. The second puck rebounds after it collides with the right shoe. If each hockey puck has the same incoming speed, which shoe has greater speed after the collision?
The right shoe
How would reversing the wheel's initial direction of rotation affect the result?
The seated demonstrator would rotate clockwise at the same angular speed.
A heavy boy and a lightweight girl are balanced on a massless seesaw. The boy moves backward, increasing his distance from the pivot point. What happens to the seesaw?
The side the boy is sitting on will tilt downward.
Water flows through a horizontal pipe. The diameter of the pipe at point B is larger than the diameter of the pipe at point A. Where is the speed of the water the greatest?
The speed of the water is the greatest at point A.
A block of mass m is attached to a horizontal spring and rests on a flat, smooth surface as seen in the figure. If you push on the block in the negative x-direction and compress the spring, what is true about the work done by the spring on the block during this motion?
The spring does negative work on the block because the spring force is in the opposite direction of the block's displacement.
Three block have masses of m1=8kg, m2=6kg, and m3=4kg are on a frictionless floor. There is a 36N horizontal force the the right of the left face of m1. What is the magnitude and direction of the force by the second block (m2) on the first block? a) 20N b) 24N c) 28N d) 32 N e) 36N aa) to the left bb) to the right
a) 20N aa) to the left
A 2.0kg mass is attached to two collinear horizontally mounted perfect Hooke's law springs with spring constants of 33 and 66 N/m. The net force on the mass is zero and this is considered the equilibrium position. The mass is now displaced 1.0m to the right of its equilibrium position. What is the magnitude of the total restoring force by the two springs? a) 99N b) 66N c) 33N d) 22N
a) 99N
A large stone disk is viewed from above and is initially at rest as seen in the figure below. The disk has a mass of 215.0 kg and a radius of 1.600 m. A constant force of 40.0 N is applied tangent to the edge of the disk for 58.0 s, causing the disk to spin around the z axis. What is (the magnitude of) the angular acceleration of the stone? a. 0.23 rad/s2 b. 1.57 rad/s2 c. 0.42 rad/s2 d. 2.01 rad/s2
a. 0.23 rad/s2
A student sits on a freely rotating stool holding two dumbbells. While rotating, he is changing between two poses. In pose A, he holds the dumbbells close to his body and in pose B, he extends his arms (see figures). In comparing the kinetic energy (KE) of the (student+stool+dumbbells) system between the two poses, which of the following relationships is true? a. KEA>KEB b. KEA<KEB c. KEA=KEB
a. KEA>KEB
Suppose we replace both hover pucks with pucks that are the same size as the originals but twice as massive. Otherwise, we keep the experiment the same. Compared to the pucks in the video, this pair of pucks will rotate
at the same rate.
The graph shows the potential energy curve of a particle moving along the x-axis under the influence of a single conservative force. At which values of x is the magnitude of the force a minimum?
at the top or bottom of a peak, when the slope is 0
a box is sitting in the back of a truck which accelerates forwards after a traffic light turns green. The road and the truck bed are horizontal. Which of the following statements is correct if the box begins to slip? a) the force of the kinetic friction by the truck on the box is in the backwards direction. b) the force of the kinetic friction by the truck on the box is in the forwards direction. c) the force of the static friction by the truck on the box is in the backwards direction. d) the force of the static friction by the truck on the box is in the forwards direction.
b) the force of the kinetic friction by the truck on the box is in the forwards direction.
During a dorm rearrangement, a TV of 10 kg, initially rests on a stand of 0.2m high, is being gently relocated to a table of 1.2m high. What is the work done by the mover on the TV during the process? (Assume an orderly moving process. The TV is not dropped or otherwise damaged.) a. 0 b. 98 J c. -98 J d. Can not be determined as the question does not specify the relative position of the table and the stand. (besides, the exact path is not given either.) e. none of above is correct.
b. 98 J
For a multi-particle system, which of the following conditions can never exist? a. The system's linear momentum is zero but its kinetic energy is not zero. b. The system's linear momentum is zero but its angular momentum is not zero. c. The system's linear momentum is zero but the total external force is not zero. d. The system's linear momentum is zero but its center of mass velocity is not zero e. Two or more of above cannot possibly happen.
d. The system's linear momentum is zero but its center of mass velocity is not zero
Your spaceship is approaching a ring of asteroids. The trajectory of the ship coincides with the line perpendicular to the plane of the ring and passes through its center. Consider that the asteroids are evenly distributed in the ring and the ship is close to the center of the ring. How does the gravitational force exerted by the ring on the ship change?
decreases
an object moves with decreasing speed. Which one of the following statements is true? a) the external/net work done on the body is positive and the kinetic energy is increasing. b) the external/net work done on the body is positive and the kinetic energy is decreasing. c) the external/net work done on the body is zero and the kinetic energy is decreasing. d) the external/net work done on the body is negative and the kinetic energy is increasing. e) the external/net work done on the body is negative and the kinetic energy is decreasing.
e) the external/net work done on the body is negative and the kinetic energy is decreasing.
Two racecars are driving at constant speeds around a circular track. Both cars are the same distance away from the center of the track, but car 2 is driving twice as fast as car 1. The acceleration of car 2 is ___________ the acceleration of car 1.
four times
Two blocks of masses m1=3.0 kg and m2 = 2.0 kg are connected by a cord that passes over a pulley as shown in the figure below. They are released from rest at the same height of 3.0m (from the bottom of the incline) and m1 starts to move lower. As the blocks are moving, what can we say about the potential energy of the m1-m2-Earth system? (ignore all frictions) a. The system's potential energy must be increasing. b. The system's potential energy must be decreasing. c. The system's potential energy must be remaining at a constant. d. We can not draw a firm conclusion as the exact value of angle θ is not given. e. none of above is correct.
b. The system's potential energy must be decreasing.
Two children are riding on a merry-go-round that is rotating with a constant angular speed. Abbie is one meter from the center of the merry-go-round, whereas Zak is two meters from the center. Abbie's acceleration is ___________ Zak's acceleration.
half of
In a perfectly ELASTIC collision between two perfectly rigid objects
both the momentum and the kinetic energy of the system are conserved.
An extended object is in static equilibrium if __________.
both the net force acting on the object is zero and the net torque acting on the object is zero
two people are at opposite ends of a massless rope. The first person is pulling the rope to the left with a force of 200N. The second person is pulling the rope to the right with a force of 200N. The tension in the rope is ___ a) 0N b) 100N c) 150N d) 200N c) 400N
d) 200N
A motorcycle drives up a steeply inclined ramp. The work done on the motorcycle by the Earth's gravitational force is ____.
negative
Block A has mass 1.00 kg and block B has mass 3.00 kg. The blocks collide and stick together on a level, frictionless surface. After the collision, the kinetic energy (KE) of block A is: one-ninth the KE of block B. one-third the KE of block B. three times the KE of block B. nine times the KE of block B. the same as the KE of block B.
one-third the KE of block B.
A constant force, F , pushes on a mass, M , which slides on a frictionless surface. At time t = 0, the mass is at rest. Which graph best shows the power delivered by the force to the mass as a function of time?
positive, increasing slope
Two boxes, one heavier than the other, are initially at rest on a horizontal frictionless surface. The same constant force F acts on each one for exactly 1 second. Which box has the most momentum after the force acts ? heavier lighter same can't tell
same
A solid sphere and a hollow sphere have the same mass and radius. They are rotating with the same angular speed. Which one has the higher angular momentum?
the hollow sphere
The sketch below shows an energy diagram in which U (x) is the potential energy of a particle of mass m as a function of location x. The particle is slowing down as it moves to the right at this location.
the least steep slope before the slop is 0
During a certain time interval, the net work done on an object is zero joules. We can be certain that ____.
the object's final speed was the same as its initial speed
a baseball abt of uniform density is cut at the location of its center of mass as shown in the figure. Which piece has the smaller mass?
the piece on the left
Two objects with different masses collide with and stick to each other. Compared to before the collision, the system of two objects after the collision has: the same amount of total momentum and the same total kinetic energy. the same amount of total momentum but less total kinetic energy. less total momentum but the same amount of total kinetic energy. less total momentum and less total kinetic energy. Not enough information is given to decide.
the same amount of total momentum but less total kinetic energy.
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 identical cars are driving in opposite directions at the same speed. Their kinetic energies have ____.
the same magnitude and sign
A solid sphere and a hollow sphere (spherical shell) of the same mass and same radius rotate with the same amount of kinetic energy. Which one is rotating faster?
the solid sphere
A ball is attached to a string and undergoing uniform circular motion on a frictionless horizontal surface. Suddenly the string breaks (in the position shown) and the ball continues on. Which of the trajectories, shown at right, best describes the motion of the ball after the string has broken?
the trajectory tangent to the point of breakage
The figure shows a system of hour particles joined by light, rigid rods. Assume all rod lengths are the same (a=b) but mass M is larger than m. About which of the coordinate axes does the system have the smallest moment of inertia?
the x axis
You observe two helium balloons floating next to each other at the ends of strings secured to a table. The facing surfaces of the balloons are separated by 1 to 2 cm. You blow through the small space between the balloons. What happens to the balloons? a. they move towards each other b. they move away from each other c. they are unaffected
they move towards each other
The Young's modulus of aluminum is 69GPa, of nylon is 3GPa, of tungsten is 400GPa, and of copper is 117GPa. If equal-size samples were put under equivalent tensile stresses, how would you rank the materials by the degree to which they would be elongated?
tungsten < copper < aluminum < nylon
The graph shows the potential energy curve of a particle moving along the x-axis under the influence of a single conservative force. At which positions of x is the speed of the particle a minimum?
when slop is 0 at the tallest part of the graph
The graph shows the potential energy curve of a particle moving along the x-axis under the influence of a single conservative force. In which intervals of x are the forces on the particle to the right?
when the slop is negative
The graph shows the potential energy curve of a particle moving along the x-axis under the influence of a single conservative force. At what one value of x is the magnitude of the force a maximum?
when the slope is at a maximum (at the steepest point)
The sketch below shows an energy diagram in which U (x) is the potential energy of a particle of mass m as a function of location x. The particle experiences the maximum magnitude force at this location
when the slope is the steepest
The sketch below shows an energy diagram in which U (x) is the potential energy of a particle of mass m as a function of location x. The particle has its maximum potential energy at this location ___
when the slope is the steepest
a small ball, hanging from the end of a rope, swings back and forth. Positions a and e are the turnaround points. Which of the following sketches best depicts the total acceleration of the ball at the specified points?
with e pointed to the right, d up and to the right, c up, b up and to the left, a to the left
Three blocks are connected as shown. The ropes and pulleys are of negligible mass. When released, block C moves downward, block B moves up the ramp, and block A moves to the right. After each block has moved a distance d, the force of gravity has done: positive work on A, B, and C. positive work on A and B, and negative work on C. zero work on A, positive work on B, and negative work on C. zero work on A, negative work on B, and positive work on C. none of these.
zero work on A, negative work on B, and positive work on C.
You have three identical balls, and three beakers containing different liquids. Each ball has a density of 600 kg/m3 . You place one ball in each beaker. In beaker A the ball floats with 50% of its volume submerged. In beaker B the ball floats with 25% of its volume submerged. In beaker C the ball sinks to the bottom. What is the density of the liquid in beaker A?
1200kg/m^3 -> displacing 1/2 volume of liquid balances whole weight of ball and liquid density = 2x ball density
A girl spins around in a circle trying to make herself dizzy. Without changing her position, she starts spinning twice as fast. By how much did her rotational kinetic energy change?
It quadrupled.
Suppose our experimenter repeats his experiment on a planet more massive than Earth, where the acceleration due to gravity is g=30 m/s2g=30 m/s2. When he releases the ball from chin height without giving it a push, how will the ball's behavior differ from its behavior on Earth? Ignore friction and air resistance. (Select all that apply.)
It will take less time to return to the point from which it was released.
A ball is thrown straight upward. How does the sign of the work done by gravity while the ball is traveling upward compare with the sign of the work done by gravity while the ball is traveling downward?
Work done by gravity is negative while the ball is traveling upward and positive while the ball is traveling downward.
If the elephant were to snorkel in salt water, which is more dense than freshwater, would the maximum depth at which it could snorkel be different from that in freshwater?
Yes, that depth would decrease, because the pressure would be higher at a given depth in salt water than in freshwater.
Suppose that we repeat the experiment in the video, but this time (1) the loop's diameter is twice that of the original loop and (2) the ball's starting position is twice as high above the table as that in the video. The initial height is sufficiently high as to allow the ball to travel all the way around the loop. How will the ball's speed at the top of the loop compare with the speed at the top of the loop in the video (v0)? Assume that we can ignore friction, and use the table as the level of zero potential energy.
sqrt(2v0)
A spring has a spring constant of 200 N/m and an equilibrium length of 5.0 m. If the final length of the spring is 9.0 m then how much potential energy does the spring have? 1600 J 2500 J 5600 J 8100 J
1600 J
Which of the following statements is true for a perfectly elastic collision in a system of particles with no net external force? (A) Both momentum and kinetic energy are conserved. (B) Momentum is conserved but kinetic energy is not conserved. (C) Kinetic energy is conserved, but momentum is not conserved. (D) The amount of momentum lost by one object is the same as the amount gained by the other object. (E) The amount of kinetic energy lost by one object is the same as the amount gained by the other object.
(A) Both momentum and kinetic energy are conserved. (D) The amount of momentum lost by one object is the same as the amount gained by the other object. (E) The amount of kinetic energy lost by one object is the same as the amount gained by the other object.
Suppose that we repeat the experiment shown in the video, but we replace one of the cylinders with a cylinder that has twice the radius (and use larger containers of water). If the height of the original cylinder is h, how deeply must we submerge the new cylinder to get the same weight reduction as in the video?
1/4 h
Consider three drinking glasses. All three have the same base area, and all three are filled to the same depth with water. Glass A is cylindrical. Glass B is wider at the top than at the bottom, so it holds more water than glass A. Glass C is narrower at the top than the bottom, so it holds less water than glass A. Which glass has the greatest liquid pressure at the bottom?
All three glasses have equal pressure at the bottom.
Which of the following situations satisfies both the first condition for equilibrium (net force = 0) and the second condition for equilibrium (net torque = 0)? A) an automobile crankshaft turning at an increasing angular speed in the engine of a parked car B) a seagull gliding at a constant angle below the horizontal and at a constant speed C) a thrown baseball that does not rotate as it sails through the air D) more than one of the above E) none of the above
B) a seagull gliding at a constant angle below the horizontal and at a constant speed
Some helicopters have two large rotors that rotate in opposite directions as shown. If instead they both rotated in the clockwise direction as seen from above, what would happen to the body of the helicopter if the pilot increased the rotation speed of both rotors?
B. The body would rotate counterclockwise.
You have three identical balls, and three beakers containing different liquids. Each ball has a density of 600 kg/m3 . You place one ball in each beaker. In beaker A the ball floats with 50% of its volume submerged. In beaker B the ball floats with 25% of its volume submerged. In beaker C the ball sinks to the bottom. Rank the liquids based on their densities, from largest to smallest.
B>A>C
If two forces of equal magnitude act on an object that is hinged at a pivot, the force acting farther from the pivot must always produce the greater torque about the pivot.
False (also depends on the angle)
Imagine that you replace the block in the video with a happy or sad ball identical to the one used as a pendulum, so that the sad ball strikes a sad ball and the happy ball strikes a happy ball. The target balls are free to move, and all the balls have the same mass. In the collision between the sad balls, how much of the balls' kinetic energy is dissipated?
Half of it
The experimenter from the video rotates on his stool, this time holding his empty hands in his lap. You stand on a desk above him and drop a long, heavy bean bag straight down so that it lands across his lap, in his hands. What happens?
He spins slower. Submit
A strong wind blows over the house shown in the figure. The wind is much stronger over the house's roof than lower down, and the house has an open chimney. A window on the ground floor is open, and so are the doors inside the house. Which way will air flow through the house?
In the window and out the chimney. Air pressure is lower at the chimney and higher outside the window, so air will flow in through the window and out through the chimney.
A DVD is rotating with an ever-increasing speed. How do the centripetal acceleration arad and tangential acceleration atan compare at points P and Q? (where Q has a larger radius than P)
Q has a greater arad and a greater atan than P.
A Ping-Pong ball hangs from a string that is attached to the rear view mirror of a parked car. The driver side window is open, and the passenger side window is closed. A strong breeze blows along the driver side of the car. What happens to the Ping-Pong ball? Assume the breeze is laminar and that Bernoulli's equation applies.
The ball swings towards the driver side. Submit
How is the angular displacement θ related to the angular velocity ω?
The change in the angular displacement over the change in time is the angular velocity.
Equal masses are suspended from two separate wires made of the same material. The wires have identical lengths. The first wire has a larger cross-sectional area than the second wire. Which wire will stretch the LEAST?
The first wire will stretch the least.
A girl and a boy are riding on a merry-go-round that is turning at a constant rate. The girl is near the outer edge, and the boy is closer to the center. Who has greater linear speed?
The girl has greater linear speed.
Two objects attract each other gravitationally. If the mass of each object doubles, how does the gravitational force between them change?
The gravitational force increases by a factor of 4.
Two identical balls are thrown vertically upward. The second ball is thrown with an initial speed that is twice that of the first ball. How does the maximum height of the two balls compare?
The maximum height of the second ball is four times that of the first ball.
The maximum stress a bone can experience before it fractures is around 10^8N/m^2 . How much stress could the bone experience if it were twice as large in diameter?
The maximum stress would be no different.
Which statement must be true for the momentum of a system to be conserved?
The net external force on the system is zero.
A constant net torque is applied to a rotating object. Which of the following best describes the object's motion?
The object will rotate with constant angular acceleration.
In both figures, a particle of mass m, is released from rest at a height, h. In figure (a), the particle is dropped straight downward and in figure (b) the particle is released from rest and slides down a ramp with a rough surface. Which particle, the one in figure (a) or (b), will have more kinetic energy at the bottom?
The particle in figure (a) will have more kinetic energy than the particle in figure (b) at the bottom.
A planet is discovered orbiting around a star in the galaxy Andromeda at the same distance from the star as Earth is from the Sun. If that star has four times the mass of our Sun, how does the orbital period of the planet compare to Earth's orbital period?
The planet's orbital period will be one-half Earth's orbital period.
Two iceboats (one of mass m, one of mass 2m) hold a race on a frictionless, horizontal, frozen lake. Both iceboats start at rest, and the wind exerts the same constant force on both iceboats. Which iceboat crosses the finish line with more kinetic energy (KE)? The iceboat of mass m: it has twice as much KE as the other. The iceboat of mass m: it has four times as much KE as the other. The iceboat of mass 2m: it has twice as much KE as the other. The iceboat of mass 2m: it has four times as much KE as the other. They both cross the finish line with the same kinetic energy.
They both cross the finish line with the same kinetic energy.
The cans have essentially the same size, shape, and mass. Which can has more energy at the bottom of the ramp? Ignore friction and air resistance. the milk, the refried beans, or they both have the same energy.
They both have the same energy.
A uniform solid sphere and a uniform hollow sphere are placed side by side at the top of an incline. If they are simultaneously released from rest and roll without slipping, which object reaches the bottom first? (ignore air friction) a. The solid sphere b. The hollow sphere c. It's a tie d. Not enough information to determine as the sizes and masses are not given.
a. The solid sphere
Consider two uniform discs A and B of the same radius. Disc A is 4 times as massive as disc B (iMA=4MB). When the discs roll down without slipping on the same incline, what can we say about their center-of-mass acceleration aCM_A and aCM_B? a. aCM_A = aCM_B b. aCM_A =2.0 aCM_B c. aCM_A = 0.5 aCM_B d. aCM_A = 4.0 aCM_B e. None of above or not enough information to determine.
a. aCM_A = aCM_B
consider an object on a rotating disk a distance r from its center, held in place on the disk by static friction. Which of the following statements is not true concerning this object? a. if the angular speed is constant, the object must have constant tangential speed b. if the angular speed is constant, the object is not accelerated c. the object has a tangential acceleration only if the disk has an angular acceleration d. if the disk has n angular acceleration, the object has both a centripetal acceleration and a tangential acceleration e. the object always has a centripetal acceleration except when the angular speed is zero
b. if the angular speed is constant, the object is not accelerated
A very massive particle M, initially at speed v, is making an elastic (1-D) collision with a very light particle m initially at rest. What is the speed of the particle m after the collision? a. ~ v b. ~ 2v c. expected to be very large, roughly equals to M/m times v d. expected to be very large, roughly equals to (M/m)2 times v e. None of above is true
b. ~ 2v
the pressure at the bottom of a filled glass of water if P. The water is poured out and the glass is filled with ethyl alcohol (density = 806). What is the pressure at the bottom of the glass? a. smaller than P b. equal to P c. larger than P
smaller than P