Deck 7: Momentum, Impulse, and Collisions

Question 1

A car wash nozzle directs a steady stream of water at 1.5 kg/s, with a speed of 20 m/s, against a car window. What force does the water exert on the glass? Assume the water does not splash back.

A) 30 N
B) 45 N
C) 300 N
D) 440 N

Answer 1

30 N

Question 2

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?

A) The kinetic energy of the rock is smaller than in the first case, but the momentum is larger.
B) The kinetic energy of the rock is smaller than in the first case, but the momenta of both are the same.
C) The kinetic energies of the rocks are the same in both cases.
D) The kinetic energy of the rock is 1/9 its previous value.

Answer 2

The kinetic energy of the rock is smaller than in the first case, but the momenta of both are the same.

Question 3

A 75-kg swimmer dives horizontally off a 500-kg raft. The diver's speed immediately after leaving the raft is 1.6 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 0.20 s, what is the magnitude of the average horizontal force by diver on the raft?

A) 900 N
B) 450 N
C) 600 N
D) 1500 N

Answer 3

600 N

Question 4

Jerome pitches a baseball of mass 0.15 kg. The ball arrives at home plate with a speed of 40 m/s and is batted straight back to Jerome with a return speed of 60 m/s. What is the magnitude of change in the ball's momentum?

A) 4.0 kg
M/s
B) 8.0 kg
M/s
C) 15 kg
M/s
D) 20 kg
M/s

Question 5

The kinetic energy of an object is quadrupled. Its momentum will change by what factor?

A) zero
B) two
C) eight
D) four

Question 6

Alex throws a 0.15-kg rubber ball down onto the floor. The ball's speed just before impact is 6.5 m/s and just after is 3.5 m/s. If the ball is in contact with the floor for 0.050 s, what is the magnitude of the average force applied by the floor on the ball?

A) 60 N
B) 133 N
C) 30 N
D) 3.5 N

Question 7

Two masses m₁ and m₂, with m₁ > m₂, have momenta with equal magnitudes. How do their kinetic energies compare?

A) KE₁ < KE₂
B) KE₁ = KE₂
C) KE₁ > KE₂
D) More information is needed.

Question 8

A 0.12-kg ball is moving at 6.0 m/s when it is hit by a bat, causing it to reverse direction and have a speed of 8.0 m/s. What is the magnitude of the change in the momentum of the ball?

A) 0.39 kg
M/s
B) 0.42 kg
M/s
C) 1.7 kg
M/s
D) 2.4 kg
M/s

Question 9

If the momentum of an object is tripled, its kinetic energy will change by what factor?

A) zero
B) one-third
C) three
D) nine

Question 10

The impulse experienced by a body is equivalent to its change in:

A) velocity.
B) kinetic energy.
C) momentum.
D) None of the other choices are valid.

Question 11

Lonnie pitches a baseball of mass 0.15 kg. The ball arrives at home plate with a speed of 40 m/s and is batted straight back to Lonnie with a return speed of 60 m/s. If the bat is in contact with the ball for 0.050 s, what is the impulse experienced by the ball?

A) 360 N·s
B) 20 N·s
C) 400 N·s
D) 15 N·s

Question 12

Alex throws a 0.43-kg rubber ball down onto the floor. The ball's speed just before impact is 6.5 m/s, and just after is 5.5 m/s. What is the magnitude of the change in the ball's momentum?

A) 0.09 kg
M/s
B) 1.0 kg
M/s
C) 4.3 kg
M/s
D) 5.2 kg
M/s

Question 13

A crane drops a 0.40-kg steel ball onto a steel plate. The ball's speeds just before impact and after are 4.5 m/s and 4.2 m/s, respectively. If the ball is in contact with the plate for 0.030 s, what is the magnitude of the average force that the ball exerts on the plate during impact?

A) 87 N
B) 116 N
C) 3.0 N
D) 3.5 N

Question 14

The dimensional equivalence of the quantity "momentum" in terms of the fundamental quantities (mass, length, time) is:

A) MLT^-1.
B) ML²T^-2.
C) MLT.
D) MLT^-2.

Question 15

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:

A) the force on the glass will be less.
B) the momentum of the paper will be greater.
C) the time for the pull will be less.
D) the coefficient of kinetic friction will be less.

Question 16

Object 1 has twice the mass of Object 2. Both objects have the same kinetic energy. Which of the following statements is true?

A) Both objects can have the same magnitude of momentum.
B) Object 1 has a momentum of greater magnitude than Object 2.
C) The magnitude of the momentum of Object 2 is four times that of Object 1.
D) All the statements are false.

Question 17

The dimensional equivalent of the quantity impulse in terms of the fundamental quantities (mass, length, time) is which of the following?

A) MLT
B) ML²T^-2
C) MLT^-1
D) MLT^-2

Question 18

A valid unit for momentum is which of the following?

A) kg
M/s²
B) kg/m²
C) kg
M/s
D) N
M

Question 19

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?

A) Both objects can have the same kinetic energy.
B) One object has 0.707 times the kinetic energy of the other.
C) One object has twice the kinetic energy of the other.
D) One object has 4 times the kinetic energy of the other.

Question 20

In an automobile collision, how does an airbag lessen the blow to the passenger? Assume as a result of the collision, the passenger stops.

A) The airbag decreases the momentum change of the passenger in the collision.
B) During the collision, the force from the airbag is greater than the force from the windshield or dashboard, so the passenger cannot hit the hard objects.
C) The stopping impulse is the same for either the hard objects or the airbag. Unlike the windshield or dashboard, the airbag gives some, increasing the time for the slowing process and thus decreasing the average force on the passenger.
D) The airbag is there to ensure the seatbelt holds.

Question 21

Ann the Astronaut weighs 60 kg. She is space-walking outside the space shuttle and pushes a 270-kg satellite away from the shuttle at 0.90 m/s. What speed does this give Ann as she moves toward the shuttle?

A) 4.0 m/s
B) 5.3 m/s
C) 8.5 m/s
D) 9.0 m/s

Question 22

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?

A) must be less
B) must also be conserved
C) may also be conserved
D) is doubled in value

Question 23

The law of conservation of momentum is applicable to systems made up of objects described by which of the following?

A) macroscopic
B) microscopic
C) interacting through friction
D) All the above choices are valid.

Question 24

A high-diver of mass 80 kg jumps off a board 10 m above the water. If 1.0 s after entering the water his downward motion is stopped, what average upward force did the water exert?

A) 100 N
B) 800 N
C) 1120 N
D) No answer is correct.

Question 25

A billiard ball is moving in the x direction at 40.0 cm/s and strikes another billiard ball moving in the y direction at 30.0 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
B) some positive value
C) some negative value
D) No answer above is correct.

Question 26

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
B) one fourth
C) twice
D) four times

Question 27

A 75-kg swimmer dives horizontally off a 250-kg raft initially at rest. If the diver's speed immediately after leaving the raft is 2 m/s, what is the corresponding raft speed?

A) 0.2 m/s
B) 0.3 m/s
C) 0.6 m/s
D) 4.0 m/s

Question 28

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 second ball moves at 50.0 cm/s, and the first ball stops. In what final direction does the second ball move?

A) in the x direction
B) at an angle of 45.0^o ccw from the x direction
C) at an angle of 53.1^o ccw from the x direction
D) Such a collision cannot happen.

Question 29

An object of mass m moving at speed v strikes and object of mass 2m which had been at rest. The first object bounces backward along its initial path at speed v. Is this collision elastic, and if not, what is the change in kinetic energy of the system?

A) The collision is elastic.
B) The kinetic energy decreases by mv².
C) The kinetic energy decreases by 1/2 mv².
D) The kinetic energy increases by mv².

Question 30

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?

A) v
B) v/3
C) 3v/4
D) 3v

Question 31

An unfueled 1000-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?

A) 1.1 * 10⁵ kg·m/s
B) 1.6 * 10⁵ kg·m/s
C) 1.5 *10⁵ kg·m/s
D) 1.9 *10⁵ kg·m/s

Question 32

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?

A) 0, because the before and after momenta cancel each other.
B) 8.6 kg·m/s
C) 17 kg·m/s
D) 2600 kg·m/s

Question 33

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?

A) maintains the same velocity as before
B) has one-half its initial velocity
C) comes to rest
D) moves in the opposite direction

Question 34

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?

A) must be less
B) must also be conserved
C) may also be conserved
D) is doubled in value

Question 35

A 2500-kg truck moving at 10.00 m/s strikes a car waiting at a traffic light, hooking bumpers. The two continue to move together at 6.00 m/s. What was the mass of the struck car?

A) 1730 kg
B) 1670 kg
C) 1200 kg
D) 1070 kg

Question 36

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:

A) the change in momentum is greater.
B) the change in momentum is less.
C) the time interval for stopping is greater.
D) the time interval for stopping is less.

Question 37

The units of impulse are equivalent to:

A) those of energy.
B) N·s.
C) kg·m/s.
D) those of force.

Question 38

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
B) 0.75 *10⁴ N
C) 0.60 * 10⁴ N
D) 0.35 * 10⁴ N

Question 39

A 30-kg object sitting at rest is struck elastically in a head-on collision with a 10-kg object initially moving at +3.0 m/s. Find the final velocity of the 30 kg object after the collision.

A) "-1.0 m/s"
B) "+1.2 m/s"
C) "+1.5 m/s"
D) "+2.0 m/s"

Question 40

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 1.8 * 10⁶ m/s, what is the speed of the thorium nucleus?

A) 1.0 *10⁴ m/s
B) 3.1 * 10⁴ m/s
C) 3.6* 10⁴ m/s
D) 4.1 *10⁴ m/s

Question 41

Three masses are moving along the x-axis. Their masses and velocities are: with , with , and with (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?

A) 0, since their combined momentum is zero.
B)
C)
D)

Question 42

Two skaters, both of mass 75 kg, are initially at rest on skates on a frictionless ice pond. One skater throws a 0.3-kg ball at 10 m/s to his friend, who catches it and throws it back at 10 m/s. When the first skater has caught the returned ball, what is the velocity of each of the two skaters?

A) 0.08 m/s, moving apart
B) 0.04 m/s, moving apart
C) 0.08 m/s, moving towards each other
D) 0.04 m/s, moving towards each other

Question 43

In a completely inelastic collision between two objects where the mass of one is double that of the other, which of the following statements is always true?

A) The larger mass will always lose kinetic energy.
B) The smaller mass will always gain kinetic energy.
C) The momentum of the smaller mass will have a larger magnitude change than that of the larger mass.
D) Not even one of the above statements is true.

Question 44

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 original kinetic energy is retained by the neutron?

A) 14.4%
B) 28.4%
C) 41.4%
D) 71.6%

Question 45

A 7.0-kg bowling ball strikes a 2.0-kg pin. The pin flies forward with a velocity of 6.0 m/s; the ball continues forward at 5.0 m/s. What was the original velocity of the ball?

A) 4.0 m/s
B) 5.7 m/s
C) 6.7 m/s
D) 3.3 m/s

Question 46

When a collision is completely inelastic, then:

A) all the kinetic energy is conserved.
B) all the kinetic energy is gone.
C) the participants stick together.
D) the total momentum is zero.

Question 47

In a system with two moving objects, when a collision occurs between the objects:

A) the total kinetic energy is always conserved.
B) the total momentum is always conserved.
C) the total kinetic energy and total momentum are always conserved.
D) neither the kinetic energy nor the momentum is conserved.

Question 48

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?

A) Yes, if the less massive particle is the one initially at rest.
B) Yes, if the more massive particle is the one initially at rest.
C) Yes, if the two particles have the same mass.
D) No, kinetic energy is always lost is such a collision.

Question 49

A billiard ball (Ball #1) moving at 5.00 m/s strikes a stationary ball (Ball #2) of the same mass. After the elastic collision, Ball #1 moves at a speed of 3.50 m/s. Find the speed of Ball #2 after the collision.

A) 1.25 m/s
B) 1.50 m/s
C) 2.16 m/s
D) 3.57 m/s

Question 50

Two billiard balls have velocities of 2.0 m/s and -1.0 m/s when they meet in an elastic head-on collision. What is the final velocity of the second ball after collision?

A) "-2.0 m/s"
B) "-1.0 m/s"
C) "-0.5 m/s"
D) "+1.0 m/s"

Question 51

A 1000-kg vehicle is moving in the positive y-direction along the y-axis at 10 m/s. A 2000-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 as measured counterclockwise from the x-axis immediately after the collision. What is the value of ?

A) 2.0
B) 4.0
C) 0.50
D) 0.25

Question 52

Kaitlin uses a bat to hit a thrown baseball. She knocks the ball back in the direction from which it came in an 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?

A) The ball was moving faster before it was hit.
B) The ball was moving faster after it was hit.
C) The ball was moving at essentially the same speed before and after the hit.
D) There is insufficient information to answer this problem.

Question 53

A 1.00-kg duck is flying overhead at 1.50 m/s when a hunter fires straight up. The 0.0100-kg bullet is moving 200 m/s when it hits the duck and stays lodged in the duck's body. What is the speed of the duck and bullet immediately after the hit?

A) 1.49 m/s
B) 1.80 m/s
C) 2.48 m/s
D) 2.50 m/s

Question 54

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 slower after the collision?

A) The less massive one.
B) The more massive one.
C) The speeds will be the same after the collision.
D) There is no way to be sure without the actual masses.

Question 55

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:

A) is moving to the right.
B) is moving to the left.
C) is at rest.
D) has less kinetic energy than the system had before the collision.

Question 56

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:

A) the basketball falls farther than the tennis ball.
B) the tennis ball is slightly shielded from the Earth's gravitational pull.
C) the massive basketball transfers momentum to the lighter tennis ball.
D) the tennis ball has a smaller radius.

Question 57

A 0.10-kg object moving initially with a velocity of +0.20 m/s makes an elastic head-on collision with a 0.15-kg object initially at rest. What percentage of the original kinetic energy is gained by the 0.15-kg object?

A) "4%"
B) "-4%"
C) "50%"
D) "96%"

Question 58

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?

A) "Neither is moving."
B) "-14 m/s, 14 m/s"
C) "+4 m/s, -4 m/s"
D) "-4 m/s, +4 m/s"

Question 59

A baseball infielder, mass 75.0 kg, jumps up with velocity 2.00 m/s and catches a 0.150-kg baseball moving horizontally at 50.0 m/s. Of the following, which is closest to the final momentum of the system, infielder and baseball?

A) 158 kg
M/s
B) 155 kg
M/s
C) 152 kg
M/s
D) 150 kg
M/s

Question 60

Two particles collide, one of them initially being at rest. Is it possible for both particles to be at rest after the collision?

A) If the collision is perfectly inelastic, then this happens.
B) If the collision is elastic, then this happens.
C) This can happen sometimes if the more massive particle was at rest.
D) No.

Question 61

Three masses are positioned along the x-axis. Their masses and positions are: with , with , and with . What is the x-coordinate of center of mass of this system?

A) (14/3) m
B) (7/3) m
C) 2 m
D) Not enough information is given to answer this question.

Question 62

In an inelastic collision between two objects with unequal masses:

A) the velocity of one will increase by the amount that the velocity of the other decreases.
B) the momentum of one will increase by the amount that the momentum of the other decreases.
C) the energy of one increases by the amount that the energy of the other decreases.
D) the total momentum of the system will decrease.

Question 63

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?

A) The clay experiences a greater change in momentum than the ball.
B) The ball experiences a greater change in momentum than the clay.
C) The clay and the ball experience the same change in momentum.
D) It is not possible to know which object has the greater change in momentum.

Question 64

A cannon of mass 1500 kg fires a 10-kg shell with a velocity of 200 m/s at an angle of 30 $\degree$ above the horizontal. Find the recoil velocity of the cannon across the level ground.

A) 1.15 m/s
B) 0.94 m/s
C) 2.41 m/s
D) 1.94 m/s

Question 65

Popeye, of mass 70 kg, has just downed a can of spinach. He accelerates quickly and stops Bluto, of mass 700 kg (Bluto is very dense), who is charging in at 5.0 m/s. What was Popeye's remarkable speed?

A) 10 m/s
B) 31 m/s
C) 50 m/s
D) 100 m/s

Question 66

A miniature, spring-loaded, radio-controlled gun is mounted on an air puck. The gun's bullet has a mass of 5.00 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 gun-puck-bullet system, what percentage is in the bullet?

A) 50%
B) 96%
C) 3.4%
D) 100%

Question 67

A miniature spring-loaded, radio-controlled gun is mounted on an air puck. The gun's bullet has a mass of 5.00 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. What is the bullet's speed?

A) 4.80 m/s
B) 13.0 m/s
C) 48.0 m/s
D) 12.5 m/s

Question 68

A 6-kg object is moving to the right at 4 m/s and collides with a 4-kg object moving to the left at 6 m/s. The objects collide and stick together. After the collision, the combined object:

A) has the same kinetic energy that the system had before the collision.
B) has more kinetic energy than the system had before the collision.
C) has no kinetic energy.
D) has less momentum than the system had before the collision.

Question 69

A 4.0 ft by 8.0 ft sheet of plywood of uniform density and thickness lies in the 1^st quadrant with its long side along the x axis, one corner at the origin, and the diagonally opposite corner at position (x, y) = (8.0 ft, 4.0 ft). The lower right 2.0 ft by 4.0 ft quarter of the sheet is removed from the sheet. What are the coordinates of the center of mass of the remaining portion of the sheet?

A) (2.0 ft, 4.0 ft)
B) (1.0 ft, 2.0 ft)
C) (3.3 ft, 1.7 ft)
D) (3.3 ft, 2.3 ft)

Question 70

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?

A) The one with mass m₁ receives the greatest impulse.
B) The one with mass m₃ receives the greatest impulse.
C) The all must receive equal impulses.
D) Although one or more of the above statements could be true in special cases, they are not always true.

Question 71

A machine gun is attached to a railroad flatcar that rolls with negligible friction. If the railroad car has a mass of 6.25 * 10⁴ kg, how many bullets of mass 25 g would have to be fired at 250 m/s off the back to give the railroad car a forward velocity of 0.3 m/s?

A) 400
B) 2000
C) 3000
D) 5000

Question 72

A 90-kg halfback running north with a speed of 10 m/s is tackled by a 120-kg opponent running south at 5.0 m/s. The collision is perfectly inelastic. Compute the velocity of the two players just after the tackle.

A) 1.4 m/s south
B) 2.8 m/s south
C) 2.8 m/s north
D) 1.4 m/s north

Question 73

During a snowball fight, two balls with masses of 0.4 and 0.6 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 20 m/s. What is the speed of the 1.0-kg mass immediately after collision?

A) zero
B) 3 m/s
C) 4 m/s
D) 5 m/s

Question 74

A 20-g bullet moving at 1000 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?

A) 10 kJ
B) 9.8 kJ
C) 0.16 kJ
D) 0.13 kJ

Question 75

A 20-g bullet moving at 1000 m/s is fired through a one-kg block of wood emerging at a speed of 200 m/s. If the block had been originally at rest and is free to move, what is its resulting speed?

A) 800 m/s
B) 80 m/s
C) 16 m/s
D) 8 m/s

Question 76

A "double satellite" is launched into space. It consists of a satellite of mass m and another satellite of mass 5m. The connecting mechanism of these satellites is an explosive bolt and a compressed spring, both of negligible mass. The bolt is exploded and the satellites drift apart having been pushed by the spring. When the less massive satellite has moved a distance of 2.5 m from the center of mass of the double satellite, how far away from it is the satellite of greater mass?

A) 3.0 m
B) 12 m
C) 0.10 m
D) 0.50 m

Question 77

A 20-g bullet moving at 1000 m/s is fired through a one-kg block of wood emerging at a speed of 200 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?

A) "0 J"
B) "-9.5 kJ"
C) "9.5 kJ"
D) "-18 J"

Question 78

A 70-kg man is standing in a 20-kg boat. Thinking he is stepping out onto the dock, the man steps to the right. 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.
B) The man actually stays still while the boat moves toward the left.
C) The boat doesn't move and the man moves to the right.
D) None of the above.

Question 79

A railroad freight car, mass 15,000 kg, is allowed to coast along a level track at a speed of 2.0 m/s. It collides and couples with a 60,000-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?

A) 20%
B) 23%
C) 86%
D) 100%

Question 80

If a two-body collision is not head-on, then we may always assume that:

A) momentum is conserved.
B) kinetic energy is conserved.
C) neither momentum nor kinetic energy are conserved.
D) both momentum and kinetic energy are conserved.