A ball is dropped from a height of 20 meters. At what height does the ball have a velocity of 10 meters/second?

A. 5.1 meters

B. 9.8 meters

C. 25 meters

D. 15 meters

Answer:B

Explanation:

Initial velocity, u=0m/s

Distance, s=20m

a=+g=9.8m/s*s

Using v*v=u*u+2gs

v*v=0+2*9.8*20

v*v=392

v=19.8

When s=20m, v = 19.8m/s

Therefore when v = 10m/s, s = 10*20/19.8

s = 10.1m