A 40 g ball dropped from a certain height bounces back from the horizontal ground without losing mechanical energy. If its speed is 10 m/s just before making contact with the ground, and the average value of the force of the ground on the ball is equal to 16N while ball and wall are in contact, how long were they in contact?
| A. |
25 ms |
| B. |
50 ms |
 |
| C. |
75 ms |
| D. |
100 ms |