A ball falls from a height of 18m above the ground. Find the speed with which the ball hits the ground. ([g = 10ms^{-2}])
-
A.
9(ms^{-1}) -
B.
9.49(ms^{-1}) -
C.
13.42(ms^{-1}) -
D.
18.97(ms^{-1})
Correct Answer: Option D
Explanation
Due to conservation of energy, K.E = P.E
(frac{1}{2}mv^{2} = mgh)
(implies m times 10 times 18 = frac{1}{2}mv^{2})
(v^{2} = 2 times 10 times 18 = 360)
(v = sqrt{360} = 18.97ms^{-1})