3) A 2.0-kg skateboard is rolling across a smooth, flat floor when a child kicks it, causing it to speed up to 4.5 m/s [N], in 0.50 s, without changing direction. The average force exerted by the child on the skateboard is 6.0 N [N]. What is the initial velocity of the skateboard? 4) A karate expert attempts to break a board using a karate chop, but fails to do so. Using the concept of impulse, explain two different changes that the karate expert can make in order to break the same board. Use the following information to answer the next two questions. Two balls roll directly toward each other. The 0.25-kg ball has a speed of 1.7 m/s; the 0.18-kg ball has a speed of 2.5 m/s. After the collision, the 0.25-kg ball has reversed its direction and has a speed of 0.10 m/s. 5a) Determine the speed of the 0.18-kg ball immediately after the collision. 5b) Using your answer from question 5a), prove if this collision was eleastic or inelastic. Note: You can still recieive marks for this question if your answer from question 5a) was incorrect. Use the following information to answer the next two questions. A 35.5-g bullet is travelling at 402 m/s towards a stationary 4.50-kg block of wood. When the bullet collides with the block of wood, it embeds itself completely in the block of wood. The bullet block of wood system is then allowed to swing upwards, as shown in the diagram below. Before After 6a) Determine the maximum height, 'h', that the bullet / block of wood system can reach. 6b) Two of the physics principles numbered on the Alberta Education 'Physics Data Sheet' (displayed on the right) must be used to determine the maximum height that the bullet / block of system can reach. The two principles, in the order in which they must be used, are Physics Principles 0 Uniform motion (Fnet = 0) 1 Accelerated motion (Fnet = 0) 2 Uniform circular motion (Fnet is radially inward) 3 Work-energy theorem 4 Conservation of momentum 5 Conservation of energy 6 Conservation of mass-energy 7 Conservation of charge 8 Conservation of nucleons Number: and Physics Principle: used first used second 9 Wave-particle duality