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
