A ball is upward with such a velocity `v` that it returns to the thrower after after `3 s`. Take `g = 10 ms^-2`. Find the value of `v`.

Options

A. 15 m//s
B. 20 m//s
C. 10 m//s
D. 5 m//s

Answer

A

Explanation

Using `vec h = vec u t + (1)/(2) vec a t^2`,
Since the displacement is zero,
`0 = uT - (1)/(2) g t^2 rArr u = (gT)/(2)`
`rArr u = (10 xx 3)/(2) = 15 m//s`.