A ball is dropped from a height of 45m above the ground. Calculate the velocity of the ball just before it strikes the ground. (Neglect air resistance and take g as (10ms^{-2})
-
A.
21.2(ms^{-1}) -
B.
30(ms^{-1}) -
C.
300(ms^{-1}) -
D.
450(ms^{-1}) -
E.
900(ms^{-1})
Correct Answer: Option B
Explanation
(v^2 = u^2+2as=0^2 + 2times 10times 45 Rightarrow
v^2 = 900m^2s^{-2} Rightarrow \
v = sqrt{900m^2s^{-2}} Rightarrow
v = 30ms^{-1})