inelastic collision. to fla 28. In a physics lab, 0.30 kg puck A, moving at 5.0 m/s [W], undergoes a collision with 0.40 kg puck B, which is initially at rest. Puck A moves off at 4.2 m/s [W 30 N]. Find the final velocity of puck B. (6 marks)19. A child on a sled (m = 47.0 kg) slides down a long hill starting from a rest position at a point 10.0 m higher in elevation than his finishing point. a) What is the total mechanical energy present? (3 marks) b) Assuming that there is no friction and no external pushes, determine the child's speed at the bottom of the hill. (2 marks) c) The child's speed at the bottom of the hill is actually 5.0 m/s. Explain whether or not this defies the law of conservation of energy. (2 marks)(17 marks) 20. A spring with a force constant of 225 N/m is resting on a frictionless surface and mounted horizontally on a wall. A 1.5 kg box is pushed against the spring, compressing it 12.0 cm from equilibrium. When released, the spring pushes the box across the floor. (8 marks) a) How much force must be exerted on the spring to compress it 12.0 cm? b) How much work is done on the spring to compress it 12.0 cm? c) How much elastic potential energy is stored in the spring while it is compressed? d) Once released, what maximum speed will the box attain?iodine must submit thein to leg for marking. (20 marks) 22. To help reduce the severity of accidents, an engineering company designs large plastic barrels filled with antifreeze that can be placed in front of bridge supports. In a simple test, a 1200 kg car moving at 20 m/s [W] crashes into several barrels. The car slows down to 8.0 m/s [W) in 0.40 s. (5 marks) a) Find the average net force acting on the car during the collision. b) What would happen to the average net force if the car in the test hit a bridge support directly, instead of the barrels? Explain your reasoning. You may assume that the bridge supports are not severely damaged during the collision.