A 57g tennis ball is dropped from 1.22 m onto a hard surface, bouncing up to a maximum height of 0.70 m. a)What was the kinetic energy of the ball just before it hit the ground for the first time?
b)How much kinetic energy must the ball have when leaving the ground to bounce to the height of 0.70m?
c)Explain why the two energies in part (a) and (b) are different.

Consider two less-than-desirable options. in the first you are driving 30 mph and crash head-on into an identical car also going 30 mph. in the second option you are driving 30 mph and crash head-on into a stationary brick wall. in neither case does your car bounce off the thing it hits, and the collision time is the same in both cases. which of these two situations would result in the greatest impact force?