22. If a stone with an original velocity of 0 is falling from ?

Question

22. If a stone with an original velocity of 0 is falling from a ledge and takes 8 seconds to hit the ground, what is the final velocity of the stone?

A. 39.2 m/s

B. 42.6 m/s

C. 78.4 m/s

D. 156.8 m/s

Answer 1

Your working formula is

Vf - Vo = gt

where

Vf = final velocity

Vo = initial velocity = 0 (given)

g =  acceleration due to gravity = 9.8 m/sec^2 (given)

t = time to reach the ground = 8sec (given)

Substituting values,

Vf - 0 = (9.8)(8)

Vf = 78.4 m/sec --- this is option C in your choices.

Answer 2

v = u + at

= 0 + 9.8 x 8

= 78.4 m/s   (C)