PHYS 234 EXAM 2 MC
15) Two objects of different mass have equal, non-zero kinetic energies. Which object has the greater magnitude momentum? A) the heavier object B) the lighter object C) They both have the same magnitude momentum.
Answer:
1) A tiger is running in a straight line. If we double both the mass and speed of the tiger, the magnitude of its momentum will increase by what factor? A) sqrt 2 B) 2 C) 4 D) 8 E) 16
Answer: 4
100) The density of material at the center of a neutron star is approximately 1.00 × 1018 kg/m3. What is the mass of a cube of this material that is on each side. (One micron is equal to 1.00 × 10-6 m.) A) 5.45 kg B) 4.74 kg C) 6.16 kg D) 6.70 kg
Answer: A
13) A rubber ball bounces off of a wall with an initial speed v and reverses its direction so its speed is v right after the bounce. As a result of this bounce, which of the following quantities of the ball are conserved? (There could be more than one correct choice.) A) the kinetic energy of the ball B) the momentum of the ball C) both the momentum and the kinetic energy of the ball D) None of the above quantities are conserved.
Answer: A
17) If you want to double the kinetic energy of a gas molecule, by what factor must you increase its momentum? A) sqrt 2 B) 2 C) 2 sqrt 2 D) 4 E) 16
Answer: A
19) A firecracker explodes in midair and breaks up into many fragments. Which of the following statements are true regarding conditions immediately before and immediately after the explosion: I. The total momentum of the fragments is equal to the original momentum of the firecracker. II. The total kinetic energy of the fragments is equal to the original kinetic energy of the firecracker. A) Statement I only B) Statement II only C) Both Statement I and Statement II D) Neither statement is true.
Answer: A
24) Consider a solid uniform sphere of radius R and mass M rolling without slipping. Which form of its kinetic energy is larger, translational or rotational? A) Translational kinetic energy is larger. B) Rotational kinetic energy is larger. C) Both are equal. D) You need to know the speed of the sphere to tell.
Answer: A
26) A disk and a hoop of the same mass and radius are released at the same time at the top of an inclined plane. If both are uniform, which one reaches the bottom of the incline first if there is no slipping? A) The hoop B) The disk C) Both reach the bottom at the same time.
Answer: A
27) A solid sphere, solid cylinder, and a hollow pipe all have equal masses and radii. If the three of them are released simultaneously at the top of an inclined plane and do not slip, which one will reach the bottom first? A) sphere B) pipe C) cylinder D) The pipe and cylinder arrive together before the sphere. E) They all reach the bottom at the same time.
Answer: A
34) Two forces produce equal torques on a door about the door hinge. The first force is applied at the midpoint of the door; the second force is applied at the doorknob. Both forces are applied perpendicular to the door. Which force has a greater magnitude? A) the first force (at the midpoint) B) the second force (at the doorknob) C) The two forces are equal.
Answer: A
35) Two equal-magnitude forces are applied to a door at the doorknob. The first force is applied perpendicular to the door, and the second force is applied at 30° to the plane of the door. Which force exerts the greater torque about the door hinge? A) the first force (applied perpendicular to the door) B) the second force (applied at an angle) C) Both forces exert equal non-zero torques. D) Both forces exert zero torque.
Answer: A
41) A merry-go-round spins freely when Diego moves quickly to the center along a radius of the merry-go-round. As he does this, it is true to say that A) the moment of inertia of the system decreases and the angular speed increases B) the moment of inertia of the system decreases and the angular speed decreases C) the moment of inertia of the system decreases and the angular speed remains the same D) the moment of inertia of the system increases and the angular speed increases E) the moment of inertia of the system increases and the angular speed decreases
Answer: A
46) A spinning ice skater on extremely smooth ice is able to control the rate at which she rotates by pulling in her arms. Which of the following statements are true about the skater during this process? (There could be more than one correct choice.) A) Her angular momentum remains constant. B) Her moment of inertia remains constant. C) Her kinetic energy remains constant. D) She is subject to a constant non-zero torque.
Answer: A
49) When you ride a bicycle, in what direction is the angular velocity of the wheels? A) to your left B) to your right C) forwards D) backwards E) up
Answer: A
5) A very light ping-pong ball moving east at a speed of 4 m/s collides with a very heavy stationary bowling ball. The Ping-Pong ball bounces back to the west, and the bowling ball moves very slowly to the east. Which object experiences the greater magnitude impulse during the collision? A) Neither; both experienced the same magnitude impulse. B) the Ping-Pong ball C) the bowling ball D) It is impossible to tell since the actual mass values are not given. E) It is impossible to tell since the velocities after the collision are unknown.
Answer: A
50) What is the angular speed, in rad/s, of a flywheel turning at 813.0 rpm? A) 85.14 rad/s B) 13.53 rad/s C) 63.84 rad/s D) 95.33 rad/s
Answer: A
51) A chicken is running in a circular path with an angular speed of 1.52 rad/s. How long does it take the chicken to complete one revolution? A) 4.13 s B) 2.07 s C) 118 s D) 4.77 s E) 8.26 s
Answer: A
55) An electrical motor spins at a constant of the edge of the rotor? A) 5707 m/s2 B) 281.6 m/s2 C) 572,400 m/s2 D) 28.20 m/s2
Answer: A
59) Tensile strain is A) the ratio of the change in length to the original length. B) the stress per unit area. C) the applied force per unit area. D) the ratio of stress to elastic modulus.
Answer: A
60) Which one of the following is an accurate statement? A) The ratio of tensile stress to tensile strain is called Young's modulus. B) "Strain" has a meaning very close to "force." C) "Stress" has a meaning very close to "stretch." D) Tensile stress is measured in newtons. E) Tensile strain is measured in meters.
Answer: A
71) Two blocks are made of the same material, but one has twice the volume of the other block. Which block will have the greater shear modulus? A) It will be the same for both of them. B) the larger one C) the smaller one
Answer: A
75) An air bubble underwater has the same pressure as that of the surrounding water. As the air bubble rises toward the surface (and its temperature remains constant), the volume of the air bubble A) increases. B) decreases. C) remains constant. D) increases or decreases, depending on the rate it rises.
Answer: A
81) A waiter fills your water glass with ice water (containing many ice cubes) such that the liquid water is perfectly level with the rim of the glass. As the ice melts, A) the liquid-water level remains flush with the rim of the glass. B) the liquid water level rises, causing water to run down the outside of the glass. C) the liquid-water level decreases.
Answer: A
87) A steel ball sinks in water but floats in a pool of mercury, which is much denser than water. Where is the buoyant force on the ball greater? A) floating on the mercury B) submerged in the water C) It is the same in both cases. D) It cannot be determined from the information given.
Answer: A
88) A 10-kg piece of aluminum sits at the bottom of a lake, right next to a 10-kg piece of lead, which is much denser than aluminum. Which one has the greater buoyant force on it? A) the aluminum B) the lead C) Both have the same buoyant force. D) It cannot be determined without knowing their volumes.
Answer: A
99) A compressed gas with a total mass of is stored in a spherical container having a radius of 0.521 m. What is the density of the compressed gas? A) 181 kg/m3 B) 110 kg/m3 C) 134 kg/m3 D) 161 kg/m3
Answer: A
79) A closed cubical chamber resting on the floor contains oil and a piston. If you push down on the piston hard enough to increase the pressure just below the piston by an amount Δp, which of the following statements is correct? (There could be more than one correct choice.) A) The pressure everywhere in the oil will increase by Δp. B) The pressure at the bottom of the oil will increase by more than Δp. C) The pressure at the top of the oil will increase by less than Δp. D) The pressure on the sides of the chamber will not increase. E) The increase in the force on the top of the chamber will be the same as the increase in the force on the bottom of the chamber.
Answer: A and E
45) A ballet dancer is spinning in the middle of a horizontal frictionless stage. Which of the following things could he change by moving parts of his body or his whole body? (There could be more than one correct choice.) A) his total kinetic energy B) his translational kinetic energy C) his rotational kinetic energy D) his angular momentum E) his moment of inertia F) the horizontal component of his linear momentum G) the location of his center of mass (or center of gravity)
Answer: A, B, C, D, E
11) If a quantity you calculated had units of kg ∙ m/s, what type of quantity could it be? (There could be more than one correct choice.) A) momentum B) kinetic energy C) work D) impulse E) force
Answer: A, D
12) A railroad car collides with and sticks to an identical railroad car that is initially at rest. After the collision, the kinetic energy of the system A) is the same as before. B) is half as much as before. C) is one third as much as before. D) is one fourth as much as before. E) is one quarter as much as before.
Answer: B
16) Two objects of different masses have momentum of equal, non-zero magnitude. Which object has more kinetic energy? A) the heavier object B) the lighter object C) They both have the same kinetic energy.
Answer: B
21) A 0.330-kg volleyball is thrown vertically downward with a speed of 0.150 m/s in a place where g = 9.81 m/s2. It takes it 0.0655 s to reach the ground. What is the magnitude of its momentum just before it hits the ground? A) 0.212 kg ∙ m/s B) 0.262 kg ∙ m/s C) 0.163 kg ∙ m/s D) 0.0216 kg ∙ m/s E) 0.0418 kg ∙ m/s
Answer: B
25) A solid sphere and a solid cylinder, both uniform and of the same mass and radius, roll without slipping at the same forward speed. It is correct to say that the total kinetic energy of the solid sphere is A) more than the total kinetic energy of the cylinder. B) less than the total kinetic energy of the cylinder. C) equal to the total kinetic energy of the cylinder.
Answer: B
3) A rocket explodes into two fragments, one 25 times heavier than the other. The magnitude of the momentum change of the lighter fragment is A) 25 times as great as the momentum change of the heavier fragment. B) The same as the momentum change of the heavier fragment. C) 1/25 as great as the momentum change of the heavier fragment. D) 5 times as great as the momentum change of the heavier fragment. E) 1/4 as great as the momentum change of the heavier fragment.
Answer: B
31) Suppose a solid uniform sphere of mass M and radius R rolls without slipping down an inclined plane starting from rest. The angular velocity of the sphere at the bottom of the incline depends on A) the mass of the sphere. B) the radius of the sphere. C) both the mass and the radius of the sphere. D) neither the mass nor the radius of the sphere.
Answer: B
32) A uniform ball is released from rest on a no-slip surface, as shown in the figure. After reaching its lowest point, the ball begins to rise again, this time on a frictionless surface. When the ball reaches its maximum height on the frictionless surface, it is A) higher than when it was released. B) lower than when it was released. C) at the same height from which it was released. D) It is impossible to tell without knowing the mass of the ball. E) It is impossible to tell without knowing the radius of the ball.
Answer: B
33) Two uniform solid balls, one of radius R and mass M, the other of radius 2R and mass 8M, roll down a high incline. They start together from rest at the top of the incline. Which one will reach the bottom of the incline first? A) The small sphere arrives first. B) Both reach the bottom at the same time. C) The large sphere arrives first.
Answer: B
48) As you are leaving a building, the door opens outward. If the hinges on the door are on your right, what is the direction of the angular velocity of the door as you open it? A) up B) down C) to your left D) to your right E) forwards
Answer: B
52) At a certain instant, a compact disc is rotating at 210 rpm. What is its angular speed in rad/s? A) 11 rad/s B) 22 rad/s C) 45 rad/s D) 69 rad/s E) 660 rad/s
Answer: B
53) When a fan is turned off, its angular speed decreases from 10 rad/s to 6.3 rad/s in 5.0 s. What is the magnitude of the average angular acceleration of the fan? A) 0.86 rad/s2 B) 0.74 rad/s2 C) 0.37 rad/s2 D) 11 rad/s2 E) 1.2 rad/s2
Answer: B
54) A child is riding a merry-go-round that is turning at 7.18 rpm. If the child is standing 4.65 m from the center of the merry-go-round, how fast is the child moving? A) 5.64 m/s B) 3.50 m/s C) 0.556 m/s D) 1.75 m/s E) 1.80 m/s
Answer: B
69) A piece of iron sinks to the bottom of a lake where the pressure is 21 times what it is at the surface of the lake. Which statement best describes what happens to the volume of that piece of iron? A) There has been no change in the volume of the iron. B) Its volume decreases slightly. C) Its volume increases slightly. D) Its volume becomes 21 times greater than at the surface. E) Its volume becomes 1/21 what it was at the surface.
Answer: B
73) A 15-kg child is sitting on a playground teeter-totter, 1.5 m from the pivot. What is the magnitude of the minimum force, applied 0.30 m on the other side of the pivot, that is needed to make the child lift off the ground? A) 75 N B) 740 N C) 23 N D) 44 N E) 66 N
Answer: B
84) A boat loaded with rocks is floating in a swimming pool. If the rocks are thrown into the pool, the water level in the pool, after the rocks have settled to the bottom, A) rises. B) falls. C) stays the same.
Answer: B
86) Salt water is denser than fresh water. A ship floats in both fresh water and salt water. Compared to the fresh water, the volume of water displaced in the salt water is A) more. B) less. C) the same. D) Cannot be determined because we do not know the volume of the ship.
Answer: B
89) A piece of iron rests on top of a piece of wood floating in a bathtub. If the iron is removed from the wood, and kept out of the water, what happens to the water level in the tub? A) It goes up. B) It goes down. C) It does not change. D) It is impossible to determine from the information given.
Answer: B
93) A 50-cm3 block of wood is floating on water, and a 50-cm3 chunk of iron is totally submerged in the water. Which one has the greater buoyant force on it? A) the wood B) the iron C) Both have the same buoyant force. D) It cannot be determined without knowing their densities.
Answer: B
94) When you blow some air above a paper strip, the paper rises. This happens because A) the air above the paper moves faster and the pressure is higher. B) the air above the paper moves faster and the pressure is lower. C) the air above the paper moves faster and the pressure remains constant. D) the air above the paper moves slower and the pressure is higher. E) the air above the paper moves slower and the pressure is lower.
Answer: B
95) Water flows through a pipe. The diameter of the pipe at point B is larger than at point A. Where is the water pressure greatest? A) at point A B) at point B C) It is the same at both A and B.
Answer: B
57) A croquet mallet balances when suspended from its center of mass, as shown in the left part of the figure. If you cut the mallet into two pieces at its center of mass, as shown in the right part of the figure, how do the masses of the two pieces compare? (There could be more than one correct choice.) A) The masses are equal. B) The piece with the head of the mallet has the greater mass. C) The piece with the head of the mallet has the smaller mass. D) It is impossible to tell.
Answer: B, D
43) If the answer to your calculation has units of kg ∙ m2/s2 , what type of quantity could it be? (There could be more than one correct choice.) A) force B) work C) angular momentum D) linear momentum E) power F) rotational kinetic energy G) moment of inertia H) torque
Answer: B, F, H
14) On a horizontal frictionless air table, a puck runs into an ideal horizontal spring that is fastened to the table. The puck compresses the spring by 15 cm before coming to rest. During the compression process, which quantities are conserved? A) only the momentum of the puck B) only the kinetic energy of the puck C) only the mechanical energy (kinetic plus potential) of the puck D) the momentum and the mechanical energy of the puck E) the momentum and the kinetic energy of the puck
Answer: C
23) Consider a uniform hoop of radius R and mass M rolling without slipping. Which is larger, its translational kinetic energy or its rotational kinetic energy? A) Translational kinetic energy is larger. B) Rotational kinetic energy is larger. C) Both are equal. D) You need to know the speed of the hoop to tell.
Answer: C
28) A disk, a hoop, and a solid sphere are released at the same time at the top of an inclined plane. They are all uniform and roll without slipping. In what order do they reach the bottom? A) disk, hoop, sphere B) hoop, sphere, disk C) sphere, disk, hoop D) sphere, hoop, disk E) hoop, disk, sphere
Answer: C
42) If the answer to your calculation has units of kg x m^2/s, what type of quantity could it be? A) force B) work C) angular momentum D) linear momentum E) power F) rotational kinetic energy G) moment of inertia H) torque
Answer: C
62) A large 75-kg lighting fixture can be hung from wires of identical size and shape made of aluminum, brass, or copper. The values of Young's modulus for these metals are 0.70 × 1011 Pa (aluminum), 0.91 × 1011 (brass), and 1.1 × 1011 (copper). Which wire would stretch the least distance? A) aluminum B) brass C) copper D) They will all stretch the same distance.
Answer: C
63) A 25-kg piece of equipment can be hung by steel wires of length 1.00 m, 2.00 m, or 3.00 m. If all the wires have the same diameter, which one will stretch the greatest distance? A) the 1.00-m wire B) the 2.00-m wire C) the 3.00-m wire D) They will all stretch by the same distance.
Answer: C
65) Two wires are made out of the same metal, but one wire is twice as long as the other wire. Which wire will have the greatest elastic modulus? A) the shorter wire B) the longer wire C) It will be the same for both wires.
Answer: C
67) Two solid spheres are made from the same material, but one has twice the diameter of the other. Which sphere will have the greater bulk modulus? A) the larger one B) the smaller one C) It will be the same for both spheres.
Answer: C
68) Which one of the following would be expected to have the smallest bulk modulus? A) liquid mercury B) liquid water C) helium vapor D) solid iron E) solid uranium
Answer: C
70) A piece of iron sinks to the bottom of a lake where the pressure is 21 times what it is at the surface. Which statement best describes what happens to the density of that piece of iron? A) There has been no change in the density of the iron. B) Its density decreases slightly. C) Its density increases slightly. D) Its density becomes 21 times greater than what it was at the surface. E) Its density becomes 1/21 what it was at the surface.
Answer: C
72) As one stretches a metal wire, which condition is reached first? A) the elastic limit B) the breaking point C) the proportional limit
Answer: C
80) The water pressure to an apartment is increased by the water company. The water enters the apartment through an entrance valve at the front of the apartment. Where will the increase in the static water pressure be greatest when no water is flowing in the system? A) at a faucet close to the entrance valve B) at a faucet far from the entrance valve C) It will be the same at all faucets. D) There will be no increase in the pressure at the faucets.
Answer: C
82) A spherical ball of lead (density 11.3 g/cm3) is placed in a tub of mercury (density 13.6 g/cm3). Which answer best describes the result? A) The lead ball will float with about 83% of its volume above the surface of the mercury. B) The lead ball will float with its top exactly even with the surface of the mercury. C) The lead ball will float with about 17% of its volume above the surface of the mercury. D) The lead will sink to the bottom of the mercury.
Answer: C
83) A wooden block contains some nails so that its density is exactly equal to that of water. If it is placed in a tank of water and released from rest when it is completely submerged, it will A) rise to the surface. B) sink to the bottom. C) remain where it is released.
Answer: C
85) Salt water has greater density than fresh water. A boat floats in both fresh water and in salt water. Where is the buoyant force greater on the boat? A) in salt water B) in fresh water C) The buoyant force is the same in both cases.
Answer: C
9) A 2.0-kg ball moving eastward at 3.0 m/s suddenly collides with and sticks to a 4.0-kg ball moving northward at 2.0 m/s. What is the magnitude of the momentum of this system just after the collision? A) 14 kg ∙ m/s B) 2.0 kg ∙ m/s C) 10 kg ∙ m/s D) 6.0 kg ∙ m/s E) 8.0 kg ∙ m/s
Answer: C
90) A piece of wood is floating in a bathtub. A second piece of wood sits on top of the first piece, and does not touch the water. If the top piece is taken off and placed in the water, what happens to the water level in the tub? A) It goes up. B) It goes down. C) It does not change. D) It cannot be determined without knowing the volumes of the two pieces of wood.
Answer: C
91) As a rock sinks deeper and deeper into water of constant density, what happens to the buoyant force on it if it started above the surface of the water? A) The buoyant force keeps increasing steadily. B) The buoyant force remains constant. C) The buoyant force first increases and then remains constant. D) The buoyant force steadily decreases.
Answer: C
98) A plastic block of dimensions 2.00 cm × 3.00 cm × 4.00 cm has a mass of 30.0 g. What is its density? A) 0.80 g/cm3 B) 1.20 g/cm3 C) 1.25 g/cm3 D) 1.60 g/cm3
Answer: C
78) If atmospheric pressure increases by an amount Δp, which of the following statements about the pressure in a lake is true? (There could be more than one correct choice.) A) The absolute (total) pressure does not change. B) The absolute (total) pressure increases, but by an amount less than Δp. C) The absolute (total) pressure increases by Δp. D) The gauge pressure increases by Δp. E) The gauge pressure does not change.
Answer: C and E
4) Which of the following quantities are units of impulse? (There could be more than one correct choice.) A) N ∙ m B) kg ∙ s/m C) kg ∙ m/s D) N ∙ s E) kg ∙ m2/s2
Answer: C, D
10) An egg falls from a bird's nest in a tree and feels no effects due to the air. As it falls, A) only its kinetic energy is conserved. B) only its momentum is conserved. C) both its kinetic energy and its momentum are conserved. D) only its mechanical energy is conserved. E) both its mechanical energy and its momentum are conserved.
Answer: D
18) If you want to double the momentum of a gas molecule, by what factor must you increase its kinetic energy? A) sqrt 2 B) 2 C) 2 sqrt 2 D) 4 E) 16
Answer: D
29) A small uniform disk and a small uniform sphere are released simultaneously at the top of a high inclined plane, and they roll down without slipping. Which one will reach the bottom first? A) the one of smallest diameter B) the one of greatest mass C) the disk D) the sphere E) They will reach the bottom at the same time.
Answer: D
30) Suppose a uniform solid sphere of mass M and radius R rolls without slipping down an inclined plane starting from rest. The linear velocity of the sphere at the bottom of the incline depends on A) the mass of the sphere. B) the radius of the sphere. C) both the mass and the radius of the sphere. D) neither the mass nor the radius of the sphere.
Answer: D
40) A person sits on a freely spinning lab stool that has no friction in its axle. When this person extends her arms, A) her moment of inertia decreases and her angular speed increases. B) her moment of inertia decreases and her angular speed decreases. C) her moment of inertia increases and her angular speed increases. D) her moment of inertia increases and her angular speed decreases. E) her moment of inertia increases and her angular speed remains the same.
Answer: D
47) When is the angular momentum of a system constant? A) Only when its total kinetic energy is constant. B) Only when no net external force acts on the system. C) Only when the linear momentum and the energy are constant. D) Only when no net external torque acts on the system. E) Only when the moment of inertia is constant.
Answer: D
56) When a car is weighed, it is driven slowly on a horizontal floor over a scale that records a reading as the front wheels go over the scale, and then records a second reading as the rear wheels go over the scale. The weight of the car is equal to A) the weight under the front wheels. B) the weight under the rear wheels. C) the average of the two weights. D) the sum of the two weights. E) the difference of the two weights.
Answer: D
58) Tensile stress is A) the strain per unit length. B) the same as force. C) the ratio of the change in length. D) applied force per cross-sectional area.
Answer: D
64) A 25-kg piece of equipment can be hung by steel wires of length 1.00 m, 2.00 m, or 3.00 m. If all the wires have the same diameter, which one will stretch the greatest percent? A) the 1.00-m wire B) the 2.00-m wire C) the 3.00-m wire D) They will all stretch by the same percent.
Answer: D
66) Which of the following are SI units of Young's modulus? (There could be more than one correct choice.) A) N/m ∙ s2 B) kg/m2 C) kg ∙ m/s2 D) kg/m ∙ s2 E) kg ∙ m2/s2
Answer: D
2) A small car meshes with a large truck in a head-on collision. Which of the following statements concerning the momentum during the collision are correct? (There could be more than one correct choice.) A) The momentum of the truck is conserved. B) The momentum of the car is conserved. C) The car and the truck must undergo the same change in speed. D) The momentum of the car and the momentum of the truck are each conserved. E) The momentum of the car-truck system is conserved, but the momentum of each one separately is not conserved.
Answer: E
74) Consider a brick that is totally immersed in water, with the long edge of the brick vertical. The pressure on the brick is A) the same on all surfaces of the brick. B) greatest on the face with largest area. C) greatest on the top of the brick. D) greatest on the sides of the brick. E) greatest on the bottom of the brick.
Answer: E
