Study Guide Questions

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

A) 5.45 kg

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.

A) Her angular momentum remains constant

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

A) It will be the same for both of them.

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. 4 A) Statement I only B) Statement II only C) Both Statement I and Statement II D) Neither statement is true.

A) Statement I only

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.

A) The hoop moment of inertia of disk I = ( 1/ 2) mr^ 2 moment of inertia of hoop I ' = mr^ 2 from law of conservation of angular momentum , Iw = I ' w' I ' > I So, w ' < w i.e., angular speed of hoop is less than disk So, disk reaches the bottom first

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

A) Translational kinetic energy is larger. (I = 2/5MR²)

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.

A) floating on the mercury

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)

A) his total kinetic energy B) his translational kinetic energy C) his rotational kinetic energy D) his angular momentum E) his moment of inertia

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.

A) sphere (the fraction winds up in a denominator for v, the larger it is, the slower v is)

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

A) the aluminum

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.

A) the first force (at the midpoint)

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

A) the moment of inertia of the system decreases and the angular speed increases.

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

A) the ratio of the change in length to the original length.

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

A) to your left

17) If you want to double the kinetic energy of a gas molecule, by what factor must you increase its momentum? A)√2 B) 2 C) 2√2 D) 4 E) 16

A)√2

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.

B) Both reach the bottom at the same time.

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

B) It goes down.

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.

B) at point 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

B) down

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.

B) falls.

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.

B) less than the total kinetic energy of the cylinder.

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.

B) less.

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.

B) the iron

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.

B) the radius of the sphere.

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

B) work F) rotational kinetic energy H) torque

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.

C) Both are equal. (I of hoop = MR²) KE(rot) = ½Iω²

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

C) It does not change.

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.

C) It will be the same for both spheres.

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.

C) The buoyant force first increases and then remains constant.

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.

C) The buoyant force is the same in both cases.

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.

C) The lead ball will float with about 17% of its volume above the surface of the mercury.

42) If the answer to your calculation has units of kg ∙ m2/s, 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

C) angular momentum

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

C) copper

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

C) helium vapor

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? (disk fraction = 1/2, hoop fraction = 1, sphere fraction = 2/5) A) disk, hoop, sphere B) hoop, sphere, disk C) sphere, disk, hoop D) sphere, hoop, disk E) hoop, disk, sphere

C) sphere, disk, hoop

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

C) the 3.00-m wire

72) As one stretches a metal wire, which condition is reached first? A) the elastic limit B) the breaking point C) the proportional limit

C) the proportional limit

96) Two horizontal pipes are the same length, but pipe B has twice the diameter of pipe A. Water undergoes viscous flow in both pipes, subject to the same pressure difference across the lengths of the pipes. If the flow rate in pipe A is Q =∆V/∆t , what is the flow rate in pipe B? A) 2Q B) 4Q C) 8Q D) 16Q E) Q√2

D) 16Q

18) If you want to double the momentum of a gas molecule, by what factor must you increase its kinetic energy? A)√2 B) 2 C) 2√2 D) 4 E) 16

D) 4

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.

D) Only when no net external torque acts on the system.

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.

D) applied force per cross-sectional area.

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

D) her moment of inertia increases and her angular speed decreases.

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

D) kg/m ∙ s²

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

D) neither the mass nor the radius of the sphere

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

D) the sphere