Question

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. 156.8 m/s
C. 78.4 m/s
D. 42.6 m/s

Answer 1

I believe the answer is C - 78.4 m/s.

Answer 2

Answer:

C. 78.4 m/s

Explanation:

Kinematic analysis

Because the stone moves with uniformly accelerated movement in free fall we apply the following formula:

vf= v₀+gt Formula (1)

Where:  

t : time in seconds (s)

v₀: initial speed in m/s  

vf: final speed in m/s  

g: acceleration  due to gravity in m/s²

Data

t = 8s

v₀= 0  

g= 9,8 m/s²

Problem development

We replace data in formula (1) to calculate the final velocity of the stone:

vf= v₀+gt

vf= 0+(9.8)(8)

vf= 78.4 m/s