Question 2: a) An athlete threw the ball from the top of a roof 80 m above the ground at a speed of 95 mph. How high is the ball above the ground at a speed of 120 mph? (1 mil = 1.61 x 10 ^ 3 m, g = 9.8 m / s2, air resistance and friction are neglected) b) The potential energy of an archer bow is given by U (x) = bx ^ 2 + cx ^ 3. The distance the spring is stretched relative to its equilibrium position is indicated by x. When the archer stretches the bow by x, find the forces that the stretched bow and the archer exert on each other. c) A furniture carrier pushes a crate of 60 kg mass with a constant velocity v = 2.0 m /s on a rough inclined plane with a height of 1.0 m and a length of 2.0 m with a kinetic friction coefficient pk = 0.30. What is the change in the potential energy of the crate?