Physics - Chapter 6
69. A neutron in a nuclear reactor makes an elastic head-on collision with a carbon atom initially at rest. (The mass of the carbon atom is 12 times that of the neutron.) What fraction of the neutron's kinetic energy is transferred to the carbon atom?
b. 28.4%
74. A billiard ball is moving in the x-direction at 30.0 cm/s and strikes another billiard ball moving in the y-direction at 40.0 cm/s. As a result of the collision, the first ball moves at 50.0 cm/s, and the second ball stops. What is the change in kinetic energy of the system as a result of the collision?
a. 0
93. An unfueled 1000-kg experimental rocket sled at rest on level frictionless rails is loaded with 50 kg of propellant. It exhausts the propellant in a 20 s "burn." The rocket moves at 160 m/s after the burn. What average force is experienced by the rocket during the burn?
a. 0.80 × 104 N
84. A model car is propelled by a cylinder of carbon dioxide gas. The cylinder emits gas at a rate of 5.00 g/s with an exit speed of 80.0 m/s. The car has a mass of 455 g, including the CO2 cylinder. Starting from rest, what is the car's initial acceleration?
a. 0.879 m/s2
35. A 5.00-g bullet is fired into a 950-g block of wood suspended as a ballistic pendulum. The combined mass swings up to a height of 8.00 cm. What was the kinetic energy of the bullet immediately before the collision?
a. 1.4E+2 J
77. A baseball infielder, mass 78.0 kg, jumps up with velocity 3.50 m/s and catches a 0.195-kg baseball moving horizontally at 55.0 m/s. Of the following, which is closest to the final momentum of the system, infielder and baseball?
a. 273 kg⋅m/s
89. At liftoff, the engines of the Saturn V rocket consumed 12 500 kg/s of fuel and exhausted the combustion products at 2 700 m/s. What was the total upward force (thrust) provided by the engines?
a. 3.38E+7 N
11. A crane drops a 0.250-kg steel ball onto a steel plate. The ball's speeds just before impact and after are 4.00 m/s and 3.70 m/s, respectively. If the ball is in contact with the plate for 0.035 s, what is the magnitude of the average force that the ball exerts on the plate during impact?
a. 55.0 N
10. Alex throws a 0.250-kg rubber ball down onto the floor. The ball's speed just before impact is 5.30 m/s, and just after is 3.71 m/s. If the ball is in contact with the floor for 0.028 s, what is the magnitude of the average force applied by the floor on the ball?
a. 80.4 N
29. A uranium nucleus (mass 238 units) at rest decays into a helium nucleus (mass 4.0 units) and a thorium nucleus (mass 234 units). If the speed of the helium nucleus is 5.5 × 105 m/s, what is the speed of the thorium nucleus?
a. 9.4E+3 m/s
82. A rocket with initial mass of 3.0 × 104 kg fires its engines at t = 0. The exhaust speed of the rocket is 3.9 × 103 m/s. If the velocity of the rocket at t = 200 s is 1 500 m/s, how much fuel did it consume?
a. 9.6 × 103 kg
1. The dimensional equivalent of the quantity impulse in terms of the fundamental quantities (mass, length, time) is which of the following?
a. MLT−1
4. The dimensional equivalence of the quantity "momentum" in terms of the fundamental quantities (mass, length, time) is:
a. MLT−1.
53. Two objects, one less massive than the other, collide elastically and bounce back after the collision. If the two originally had velocities that were equal in size but opposite in direction, then which one will be moving faster after the collision?
a. The less massive one.
30. A 75-kg man is standing in a 20-kg boat. The man steps to the right thinking he is stepping out onto the dock. However, the following will actually happen (ignore the friction of the water or air on the boat or the man):
a. The man only moves a short distance to the right while the boat moves a larger distance to the left.
72. If a two-body collision is not head-on, then we may always assume that:
a. momentum is conserved.
41. A billiard ball collides in an elastic head-on collision with a second identical ball. What is the kinetic energy of the system after the collision compared to that before collision?
a. the same as
52. Two billiard balls have velocities of 4.0 m/s and -1.0 m/s when they meet in an elastic head-on collision. What is the final velocity of the first ball after collision?
b. -1.0 m/s
71. Three masses are moving along the x-axis. Their masses and velocities are m1 = m with v1 = v, m2 = 2m with v2 = 2v, and m3 = 3m with v3 = -3v (the minus sign indicating this velocity is in the negative x-direction). The three masses collide and stick together in a completely inelastic collision. What is the resultant velocity of the combined mass?
b. -2v/3
58. Two skaters, both of mass 75.0 kg, are on skates on a frictionless ice pond. One skater throws a 0.40-kg ball at 6.0 m/s to his friend, who catches it and throws it back at 6.0 m/s. When the first skater has caught the returned ball, what is the velocity of each of the two skaters?
b. 0.063 m/s, moving apart
86. A 1 500-kg experimental rocket sled at rest on level frictionless rails is loaded with 55.0 kg of propellant. It exhausts the propellant in a 20-s "burn." The rocket moves at 155 m/s after the burn. What average force is experienced by the rocket during the burn?
b. 1.16E+4 N
25. A cannon of mass 1 300 kg fires a 13.6-kg shell with a velocity of 180 m/s at an angle of 45° above the horizontal. Find the recoil velocity of the cannon across the level ground.
b. 1.33 m/s
92. An unfueled 1 000-kg experimental rocket sled on level frictionless rails is loaded with 50 kg of propellant. It exhausts the propellant in a 20-s "burn." If the rocket, initially at rest, moves at 160 m/s after the burn, what impulse is experienced by the rocket sled?
b. 1.6 × 105 kg·m/s
9. Alex throws a 0.25-kg rubber ball down onto the floor. The ball's speed just before impact is 4.5 m/s, and just after is 2.9 m/s. What is the change in the magnitude of the ball's momentum?
b. 1.9 kg⋅m/s
79. A 2 500-kg car moving north collides with a 2 000-kg car moving west. After the collision, the cars stick together and move at an angle of 45° north of west at a speed of 8.0 m/s. What was the initial speed of the 2 500-kg car?
b. 10.2 m/s
47. A 20.0-g bullet moving at 1 000 m/s is fired through a one-kg block of wood emerging at a speed of 100 m/s. If the block had been originally at rest and is free to move, what is its resulting speed?
b. 18.0 m/s
36. A man standing on frictionless ice throws a 1.00-kg mass at 29.0 m/s at an angle of elevation of 50.0°. What was the magnitude of the man's momentum immediately after throwing the mass?
b. 18.6 kg·m/s
91. A rocket of total mass M and with burnout mass 0.20M attains a speed of 3 400 m/s after starting from rest in deep space. What is the exhaust velocity of the rocket?
b. 2.1E+3 m/s
67. A railroad freight car, mass 15 000 kg, is allowed to coast along a level track at a speed of 3.0 m/s. It collides and couples with a 54 000-kg loaded second car, initially at rest and with brakes released. What percentage of the initial kinetic energy of the 15 000-kg car is preserved in the two-coupled cars after collision?
b. 22%
27. Ann the Astronaut weighs 65.0 kg. She is space walking outside the space shuttle and pushes a 350.0-kg satellite away from the shuttle at 0.70 m/s. What speed does this give Ann as she moves toward the shuttle?
b. 3.8 m/s
15. A car wash nozzle directs a steady stream of water at 1.10 kg/s, with a speed of 30.0 m/s, against a car window. What force does the water exert on the glass? Assume the water does not splash back.
b. 33.0 N
50. During a snowball fight two balls with masses of 0.30 and 0.70 kg, respectively, are thrown in such a manner that they meet head-on and combine to form a single mass. The magnitude of initial velocity for each is 12.0 m/s. What is the speed of the 1.0-kg mass immediately after collision?
b. 4.8 m/s
13. Lonnie pitches a baseball of mass 0.500 kg. The ball arrives at home plate with a speed of 35.0 m/s and is batted straight back to Lonnie with a return speed of 50.0 m/s. If the bat is in contact with the ball for 0.055 s, what is the impulse experienced by the ball?
b. 42.5 N⋅s
87. A helicopter stays aloft by pushing large quantities of air downward every second. What mass of air must be pushed downward at 35.0 m/s every second to keep a 1 500-kg helicopter aloft?
b. 420 kg
78. A disk of mass m moving in the positive x direction collides with a stationary disk, also of mass m. The first disk moves in a direction θ1 with respect to the x axis, and the second disk moves off in a direction of θ2 below the x axis, as shown in the figure. If v = 10 m/s, θ1 = 30°, and v1f = 8 m/s, what is v2f?
b. 6.1 m/s
81. A satellite engine has an exhaust speed of 2.80 × 104 m/s and ejects ionized gas at a rate of 2.50 × 10-6 kg/s. What is the instantaneous thrust of the engine?
b. 7.00 × 10-2 N
55. A 7.50-kg bowling ball strikes a 5.20-kg pin. The pin flies forward with a velocity of 4.00 m/s; the ball continues forward at 5.50 m/s. What was the original velocity of the ball?
b. 8.27 m/s
38. Object 1 has twice the mass of Object 2. Both objects have the same kinetic energy. Which of the following statements is true?
b. Object 1 has a momentum of greater magnitude than Object 2.
31. A lump of clay is thrown at a wall. A rubber ball of identical mass is thrown with the same speed toward the same wall. Which statement is true?
b. The ball experiences a greater change in momentum than the clay.
83. Neglecting gravity, doubling the exhaust velocity from a single stage rocket initially at rest changes the final velocity attainable by what factor? Assume all other variables, such as the mass of the rocket and the mass of the fuel, do not change.
b. The final velocity doubles.
18. A rock is moving with speed v. If the mass of the rock were tripled and the speed were reduced to v/3, which of the following statements would be true?
b. The kinetic energy of the rock is smaller than in the first case, but the momenta of both are the same.
73. A billiard ball is moving in the x-direction at 33.4 cm/s and strikes another billiard ball moving in the y-direction at 38.9 cm/s. As a result of the collision, the first ball moves at 50.6 cm/s, and the second ball stops. In what final direction does the first ball move?
b. at an angle of 49.4° ccw from the x-direction
43. In a two-body collision, if the kinetic energy of the system is conserved, then which of the following best describes the momentum after the collision?
b. must also be conserved
54. In a partially elastic collision between two objects with unequal mass:
b. the momentum of one will increase by the amount that the momentum of the other decreases.
65. In an inelastic collision between two objects with unequal masses:
b. the momentum of one will increase by the amount that the momentum of the other decreases.
44. In a system with two moving objects, when a collision occurs between the objects:
b. the total momentum is always conserved.
22. The kinetic energy of an object is quadrupled. Its momentum will change by what factor?
b. two
60. Two identical 7-kg bowling balls roll toward each other. The one on the left is moving at +4 m/s while the one on the right is moving at −4 m/s. What is the velocity of each ball after they collide elastically?
b. −4 m/s, +4 m/s
66. A 22.3-g bullet moving at 1 000 m/s is fired through a one-kg block of wood emerging at a speed of 100 m/s. What is the change in the kinetic energy of the bullet-block system as a result of the collision assuming the block is free to move?
c. -10.8 kJ
33. A 5.25-g bullet is fired into a 360-g block of wood suspended as a ballistic pendulum. The combined mass swings up to a height of 8.75 cm. What was the magnitude of the momentum of the combined mass immediately after the collision?
c. 0.478 kg·m/s
24. A 75.0-kg swimmer dives horizontally off a 465-kg raft initially at rest. If the diver's speed immediately after leaving the raft is 5.00 m/s, what is the corresponding raft speed?
c. 0.806 m/s
75. A 75.0-kg halfback running north with a speed of 11.0 m/s is tackled by a 80.5-kg opponent running south at 7.5 m/s. The collision is perfectly inelastic. Compute the velocity of the two players just after the tackle.
c. 1.4 m/s north
85. A 1 200-kg experimental rocket sled on level frictionless rails is loaded with 55.0 kg of propellant. It exhausts the propellant in a 20-s "burn." If the rocket, initially at rest, moves at 155 m/s after the burn, what impulse is experienced by the rocket sled?
c. 1.9E+5 kg⋅m/s
19. A soccer ball (mass = 0.43 kg) is moving at a speed of 20 m/s when it is kicked with a force of 300 N resulting in it going in the opposite direction with the same speed as before. What is the magnitude of the impulse delivered to the ball?
c. 17 kg·m/s
70. Mitch throws a 130-g lump of clay at a 590-g target, which is at rest on a horizontal surface. After impact, the target, including the attached clay, slides 2.8 m before stopping. If the coefficient of friction is μ = 0.50, find the speed of the clay before impact.
c. 29 m/s
48. A 26.0-g bullet moving at 1 200 m/s is fired through a one-kg block of wood emerging at a speed of 200 m/s. What is the kinetic energy of the block that results from the collision if the block had not been moving prior to the collision and was free to move?
c. 3.4E+2 J
80. A rocket has an exhaust speed of 2.5 × 103 m/s, and produces 7.5 × 105 N of instantaneous thrust. What mass of fuel does the rocket burn each second?
c. 300 kg/s
94. A miniature, spring-loaded, radio-controlled gun is mounted on an air puck. The gun's bullet has a mass of 6.00 g, and the gun and puck have a combined mass of 130 g. With the system initially at rest, the radio-controlled trigger releases the bullet, causing the puck and empty gun to move with a speed of 0.500 m/s. Of the total kinetic energy of the gunpuck-bullet system, what percentage is in the bullet?
c. 96%
90. Neglecting gravity, doubling the exhaust velocity from a single stage rocket initially at rest changes the final kinetic energy of the burnout stage by what factor? Assume all other variables, such as the mass of the rocket and the mass of the fuel, do not change
c. It quadruples
17. Two masses m1 and m2, with m1 < m2, have momenta with equal magnitudes. How do their kinetic energies compare?
c. KE1 > KE2
39. Object 1 has twice the mass of Object 2. Each of the objects has the same magnitude of momentum. Which of the following statements is true?
c. One object has twice the kinetic energy of the other.
16. In an automobile collision, how does an airbag lessen the blow to the passenger? Assume as a result of the collision, the passenger stops.
c. The stopping impulse is the same for either the hard objects or the airbag. Unlike the windshield or dashboard, the air bag increases the time for the slowing process and thus decreases the average force on the passenger.
40. A billiard ball collides in an elastic head-on collision with a second stationary identical ball. After the collision which of the following conditions applies to the first ball?
c. comes to rest
62. A 5-kg object is moving to the right at 4 m/s and collides with a 4-kg object moving to the left at 5 m/s. The objects collide and stick together. After the collision, the combined object:
c. has no kinetic energy.
2. A valid unit for momentum is which of the following?
c. kg⋅m/s
6. The units of impulse are equivalent to:
c. kg⋅m/s.
42. In a two-body collision, if the momentum of the system is conserved, then which of the following best describes the kinetic energy after the collision?
c. may also be conserved
3. The impulse experienced by a body is equivalent to its change in:
c. momentum.
57. A tennis ball is held above and in contact with a basketball, and then both are simultaneously dropped. The tennis ball bounces off the basketball at a fairly high speed. This is because:
c. the massive basketball transfers momentum to the lighter tennis ball.
45. When a collision is perfectly inelastic, then:
c. the participants stick together.
14. If a glass of water is on a table with a piece of paper under it, it is relatively easy to pull the paper out without disturbing the glass very much if the pull is done very quickly. This is because, with a quick pull:
c. the time for the pull will be less.
23. A moderate force will break an egg. However, an egg dropped on the road usually breaks, while one dropped on the grass usually doesn't break. This is because for the egg dropped on the grass:
c. the time interval for stopping is greater.
68. A 25.0-kg object sitting at rest is struck elastically in a head-on collision with a 20.5-kg object initially moving at +4.0 m/s. Find the final velocity of the 25.0-kg object after the collision.
d. +3.6 m/s
5. A ball with original momentum +7.0 kg⋅m/s hits a wall and bounces straight back without losing any kinetic energy. The change in momentum of the ball is:
d. -14 kg⋅m/s.
76. A 1 000-kg vehicle is moving in the positive y-direction along the y-axis at 10 m/s. A 2 000-kg vehicle is moving in the positive x-direction at along the x-axis at 20 m/s. The vehicles collide and stick together. They move as a single object in a direction θ as measured counterclockwise from the x-axis immediately after the collision. What is the value of tan θ?
d. 0.25
51. A 2 900-kg truck moving at 11.0 m/s strikes a car waiting at a traffic light, hooking bumpers. The two continue to move together at 7.00 m/s. What was the mass of the struck car?
d. 1 660 kg
7. A 70-kg swimmer dives horizontally off a 500-kg raft. The diver's speed immediately after leaving the raft is 6.0 m/s. A micro-sensor system attached to the edge of the raft measures the time interval during which the diver applies an impulse to the raft just prior to leaving the raft surface. If the time interval is read as 0.25 s, what is the magnitude of the average horizontal force by diver on the raft?
d. 1 700 N
34. A 13.4-g bullet is fired into a 1.60-kg block of wood which is suspended as a ballistic pendulum. The combined mass swings up to a height of 8.50 cm. What was the kinetic energy of the combined mass immediately after the collision?
d. 1.34 J
8. A 0.10-kg ball is moving at 7.0 m/s when it is hit by a bat, causing it to reverse direction and have a speed of 12.0 m/s. What is the change in the magnitude of the momentum of the ball?
d. 1.9 kg⋅m/s
28. A miniature spring-loaded, radio-controlled gun is mounted on an air puck. The gun's bullet has a mass of 7.00 g, and the gun and puck have a combined mass of 150 g. With the system initially at rest, the radio controlled trigger releases the bullet causing the puck and empty gun to move with a speed of 0.530 m/s. What is the bullet's speed?
d. 11.4 m/s
59. Popeye, of mass 75.0 kg, has just downed a can of spinach. He accelerates quickly and stops Bluto, of mass 650 kg (Bluto is very dense), who is charging in at 15.0 m/s. What was Popeye's speed?
d. 130 m/s
12. Jerome pitches a baseball of mass 0.300 kg. The ball arrives at home plate with a speed of 40.0 m/s and is batted straight back to Jerome with a return speed of 52.0 m/s. What is the magnitude of change in the ball's momentum?
d. 27.6 kg⋅m/s
26. A machine gun is attached to a railroad flatcar that rolls with negligible friction. If the railroad car has a mass of 6.35 × 104 kg, how many bullets of mass 35.0 g would have to be fired at 200 m/s off the back to give the railroad car a forward velocity of 0.56 m/s?
d. 5.1E+3
20. The law of conservation of momentum is applicable to systems made up of objects described by which of the following?
d. All the above choices are valid.
32. Three satellites are launched into space connected together. Once in deep space, an explosive charge separates the three satellites and they move apart. The satellites each have different masses with m1 < m2 < m3. Which of the following statements is always true?
d. Although one or more of the above statements could be true in special cases, they are not always true.
46. Two particles collide, one of them initially being at rest. Is it possible for both particles to be at rest after the collision?
d. No
63. Two masses collide and stick together. Before the collision one of the masses was at rest. Is there a situation in which the kinetic energy is conserved in such a collision?
d. No, kinetic energy is always lost is such a collision.
49. An object of mass m moving at speed v0 strikes an object of mass 2m which had been at rest. The first object bounces backward along its initial path at speed v0. Is this collision elastic, and if not, what is the change in kinetic energy of the system?
d. The kinetic energy increases by mv2.
56. Kaitlin uses a bat to hit a thrown baseball. She knocks the ball back in the direction from which it came in a partially inelastic collision. The bat, which is heavier than the baseball, continues to move in the same direction after the hit as Kaitlin "follows through." Is the ball moving faster before or after it was hit?
d. There is insufficient information to answer this problem.
61. A 5-kg object is moving to the right at 4 m/s and collides with another object moving to the left at 5 m/s. The objects collide and stick together. After the collision, the combined object:
d. has less kinetic energy than the system had before the collision.
21. If the momentum of an object is tripled, its kinetic energy will change by what factor?
d. nine
88. A model rocket sits on the launch pad until its fuel is ignited, blasting the rocket upward. During the short time of blast-off, as the ignited fuel goes down, the rocket goes up because:
d. of none of the above reasons.
64. Two masses m1 and m2, with m1 = 3 m2, undergo a head-on elastic collision. If the particles were approaching with speed v before the collision, with what speed are they moving apart after collision?
d. v
37. A high-diver of mass 59.8 kg jumps off a board 10.0 m above the water. If, 1.00 s after entering the water his downward motion is stopped, what average upward force did the water exert?
e. None of the other answers is correct.
