9. A ball is pushed down a 20.0 m hill with a speed of 15.0 m/s. If the ball has a mass of 5.5 kg. a. Calculate the total mechanical energy at the top of the hill. (3 marks) b. At what height above the ground is the ball travelling 21.0 m's? (3 marks) c. What is the speed of the ball when it reaches the ground? (2 marks) 10. Two friends are standing next to each other on ice skates, one with a mass of 62 kg and the other with a mass of 85 kg. One friend decides to push the other one. What will happen after the push, use two of Newton's laws to justify your