Question

If a ball with an original velocity of zero is dropped from a tall structure and takes 7 seconds to hit the ground, what velocity does the ball have when it reaches the ground? A. 156.8 m/s B. 68.6 m/s C. 34.3 m/s D. 240.1 m/s

Answer 1

The ball is dropped from rest, so its velocity at time
`t` is

`v=at`

where
`a=-g` is the acceleration due to gravity. After 7 seconds, we have

`v=\left(-9.8\,(\mathrm m)/(\mathrm s^2)\right)(7\,\mathrm s)`

`\implies v=68.6\,(\mathrm m)/(\mathrm s)`

so the answer is B.