A0.065-kg tennis ball moving to the right with a speed of 15 m/s is struck by a tennis racket, causing it to move to the left with a speed of 15 m/s. if the ball remains in contact with the racquet for 0.020 s, what is the magnitude of the average force exerted on the ball?

Using the formula for impulse, we can solve this problem.
In terms of change in momentum, impulse is:
I = m (v2 - v1)

Or in terms of force and contact time:
I = F t

Equating the two equations:
m (v2 - v1) = F t

Setting the right direction as positive and the left as negative, we can then substitute values with their respective signs:
0.065 (-15 -15) = F (0.020)
F = -97.5 N

The negative sign indicates that the force was directed to the left.

Wind or electric energy force force of friction