71 and 72 Momentum and Its Conservation 1. (I) What is the magnitude of the momentum of a 28g sparrow flying with a speed of 8.4 m/s? 3. (I) A 7150-kg railroad car travels alone on a level frictionless track with a constant speed of 15.0 m/s. A 3350kg load, initially at rest, is dropped onto the car. What will be the car's new speed? 5. (II) Calculate the force exerted on a rocket when the propelling gases are being expelled at a rate of 1300 kg/s with a speed of 4.5 x 104 m/s. 7. (II) A child in a boat throws a 5.30-kg package out horizontally with a speed of 10.0 m/s, Fig. 7 31. Calculate the velocity of the boat immediately after, assuming it was initially at rest. The mass of the child is 24.0 kg and the mass of the boat is 35.0 kg. \f73 Collisions and Impulse 15. 17. 19. 21. (I) A 0.145kg baseball pitched at 31.0 m/s is hit on a horizontal line drive straight back at the pitcher at 46.0 m/s. Ifthe contact time between bat and ball is 5.00 x 103 s, calculate the force (assumed to be constant) between the ball and bat. (II) A 12kg hammer strikes a nail at a velocity of7.5 m/s and comes to rest in a time interval of 8.0 ms. (or) What is the impulse given to the nail? (b) What is the average force acting on the nail? (II) A 125kg astronaut (including space suit) acquires a speed of 2.50 m/s by pushing off with her legs from a 1900kg space capsule. (a) What is the change in speed of the space capsule? (b) If the push lasts 0.600 5, what is the average force exerted by each on the other? As the reference frame, use the position of the capsule before the push. (c) What is the kinetic energy of each after the push? (II) A 95kg fullback is running at 3.0 m/s to the east and is stopped in 0.85 s by a headon tackle by a tackler running due west. Calculate (a) the original momentum of the fullback, (b) the impulse exerted on the fullback, (c) the impulse exerted on the tackler, and (d) the average force exerted on the tackler