Question

A tennis ball is dropped from 1.4 m above the
ground. It rebounds to a height of 0.856 m.
With what velocity does it hit the ground?
The acceleration of gravity is 9.8 m/s
2
. (Let
down be negative.)
Answer in units of m/s.

Answer 1

Answer:

The velocity with which the ball strikes the ground = -5.2 m/s

Explanation:

To find the velocity with which the tennis ball hits the ground, we only need to worry about what happens up to that point. We can ignore the rebound for this part. Given:

d = -1.4

a = -9.8

vi = 0

vf = ?

$v_f^2 = v_i^2 + 2ad\\v_f^2=0+2(-9.8)(-1.4)\\v_f^2=27.44\\v_f=-5.2$

*Keep in mind that the square root gives us two answers, a positive and a negative one. We use the negative one here because the final speed is downwards and the question says down is negative.