8.4 Elastic Collisions in One Dimension

Two cars (A and B) of mass 1.5 kg collide. Car A is initially moving at 12 m/s, and car B is initially moving in the same direction with a speed of 6 m/s. The two cars are moving along a straight line before and after the collision. What will be the change in momentum of this system after the collision?

1. −27 kg • m/s
2. zero
3. +27 kg • m/s
4. It depends on whether the collision is elastic or inelastic.

Puck A (200 g) slides across a frictionless surface to collide with puck B (800 g), initially at rest. The velocity of each puck is measured during the experiment as follows:

What is the change in momentum of the center of mass of the system as a result of the collision?

1. +1.6 kg•m/s
2. +0.8 kg•m/s
3. 0
4. −1.6 kg•m/s

Two cars (A and B) of equal mass have an elastic collision. Prior to the collision, car A is moving at 15 m/s in the +x-direction, and car B is moving at 10 m/s in the –x-direction. Assuming that both cars continue moving along the x-axis after the collision, what will be the velocity of car A after the collision?

1. same as the original 15 m/s speed, opposite direction
2. equal to car B’s velocity pri…

A rubber ball is dropped from rest at a fixed height. It bounces off a hard floor and rebounds upward, but it only reaches 90% of its original fixed height. What is the best way to explain the loss of kinetic energy of the ball during the collision?

1. Energy was required to deform the ball’s shape during the collision with the floor.
2. Energy was lost due to work done by the ball pushing on the floor…

Two objects, A and B, have equal mass. Prior to the collision, mass A is moving 10 m/s in the +x-direction, and mass B is moving 4 m/s in the +x-direction. Which of the following results represents an inelastic collision between A and B?

1. After the collision, mass A is at rest, and mass B moves 14 m/s in the +x-direction.
2. After the collision, mass A moves 4 m/s in the –x-direction, and mass B move…

Two objects (A and B) of equal mass collide elastically. Mass A is initially moving 5.0 m/s in the +x-direction prior to the collision. Mass B is initially moving 3.0 m/s in the –x-direction prior to the collision. After the collision, mass A will be moving with a velocity of 3.0 m/s in the –x-direction. What will be the velocity of mass B after the collision?

1. 3.0 m/s in the +x-direction
2. 5.0 m/s…

Two objects of equal mass collide. Object A is initially moving in the +x-direction with a speed of 12 m/s, and object B is initially at rest. After the collision, object A is at rest, and object B is moving away with some unknown velocity. There are no external forces acting on the system of two masses. What statement can we make about this collision?

1. Both momentum and kinetic energy are conserv…

Which of the following statements is true about an inelastic collision?

1. Momentum is conserved, and kinetic energy is conserved.
2. Momentum is conserved, and kinetic energy is not conserved.
3. Momentum is not conserved, and kinetic energy is conserved.
4. Momentum is not conserved, and kinetic energy is not conserved.

Mass A (1.0 kg) slides across a frictionless surface with a velocity of 8 m/s in the positive direction. Mass B (3.0 kg) is initially at rest. The two objects collide and stick together. What will be the change in the center-of-mass velocity of the system as a result of the collision?

1. There will be no change in the center-of-mass velocity.
2. The center-of-mass velocity will decrease by 2 m/s.
3. The c…

Two piloted satellites approach one another at a relative speed of 0.250 m/s, intending to dock. The first has a mass of $4 . \text{00} \times \text{10}^{3} \text{ kg}$, and the second a mass of $7 . \text{50} \times \text{10}^{3} \text{ kg}$. If the two satellites collide elastically rather than dock, what is their final relative velocity?