A stone is dropped from a height of 45m. Find the time it takes to hit the ground. ([g = 10 ms^{-2}])
-
A.
3.0 seconds -
B.
4.5 seconds -
C.
5.0 seconds -
D.
9.0 seconds
Correct Answer: Option A
Explanation
(s = ut + frac{1}{2}gt^{2})
(u = 0; s = 45m; g = 10ms^{-2})
(45 = 0 + frac{1}{2}(10)t^{2} = 5t^{2})
(t^{2} = frac{45}{5} = 9)
(t = 3.0s)