1. Prove these statements: (a) As long as you can neglect the effects of the air, if you throw anything vertically upward, it will have the same speed when it returns to the release point as when it was released. (b) The time of flight will be twice the time it takes to get to its highest point.2. The graph below describes the acceleration as a function of time for a stone rolling down a hill starting from rest. (a) Find the stone's velocity at t=2.5 s and at t=7.5 s. (b) Sketch a graph of the stone's velocity as a function of time. (c) Sketch a graph of the stone's displacement as a function of time. a (cm/s-) t (s) O 2 3 4 4 5 6 7 8