Question

A body projected vertically upwards with a velocity u returns to the starting point in $4 s$. If $g = 10 \,m s^{-2}$, the value of $u$ in $m/s$ is

• A. 10
• B. 5
• C. 4
• D. 20

Answer 1

Answer: (D)

20

Answer 2

Time of ascent = Time of descent = $\frac{4}{2}$ = 2 s
$\nu$ u + (-gt) i.e. 0 = u - 10 $\times$ 2 i.e. u = 20 m $s^{-1}$