PSC # 5 Momentum, Impulse and conservation of momentum

1. Train A (mass = 5000 kg) successfully couples with a Train B (mass = 7500 kg). Train A is moving at 6.0 m/s before the coupling (collision), and Train B is initially at rest. A. What is the final velocity of the coupled trains? B. What is the initial kinetic energy (KE)? C. What is the final KE? D. How much KE is lost? E. What fraction of the initial KE is lost?

2. A 35.0-g bullet strikes a 5.0-kg stationary wooden block and embeds itself in the block. The block and bullet move together at 8.6 m/s. What was the original velocity of the bullet?

3. A 65.0-kg archer, standing on frictionless ice, shoots a 250-g arrow at a speed of 125 m/s. What is the recoil speed of the archer?

4. An 80-kg man and his car are suddenly accelerated from rest to a speed of 5 m/s as a result of a rear-end collision. Assuming the time taken to be 0.3 s, find:
a) the impulse on the man and

b) the average force exerted on him by the back seat of his car.

5. A billiard ball moving at 5 m/s strikes a stationary ball of the same mass (see figure below). After the collision, the first ball moves at 4.33 m/s at an angle of 30° with respect to the original line of motion. Find the struck ball’s velocity and verify whether the collision is elastic or inelastic.

* 6. A pendulum consisting of a 0.8-kg ball attached to a string of length 2.3 m is released from rest when the string makes an angle of 53° with the vertical. At the bottom of its swing, the ball collides elastically with a block of mass m at rest on a horizontal frictionless surface. After the

collision, the maximum angle the string makes with the vertical is 5.73°. What is the mass of the block?