An object falls freely from a height of 25m onto the roof a building 5m high. Calculate the velocity with which the object strikes the roof (g=10(ms^{-2})
-
A.
17.3(ms^{-2}) -
B.
20(ms^{-2}) -
C.
24.5(ms^{-2}) -
D.
125(ms^{-2}) -
E.
200(ms^{-2})
Correct Answer: Option B
Explanation
(v^2=u^2 +2as =0 +2times(25-5)\ v^2 =0+20times 20=400;v =sqrt{400}= 20(ms^{-2})