A ball is projected horizontally from the top of a hill with a velocity of 20m-1. If it reaches the ground 4 seconds later, what is the height of the hill? (g = 10ms-2)
-
A.
20m -
B.
40m -
C.
80m -
D.
160m -
E.
200m
Correct Answer: Option C
Explanation
Initial horizontal velocity = 20ms-1
Initial vertical velocity = 0
s = ut + (frac{1}{2}gt^2) = 0 x 5 x 42
= 80m