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