Question

A body is projected horizontally from the top of a tall tower with a velocity of $30\, ms ^{-1}$. At time $t_{1}$, its horizontal and vertical components of the velocity are equal and at time $t_{2}$, its horizontal and vertical displacements are equal. Then $t_{2}-t_{1}$ is (take, $\left. g=10\, ms ^{-2}\right)$

• A. 1 s
• B. 1.5 s
• C. 2 s
• D. 3 s

Answer 1

Answer: (D)

As per first condition,
$30=10\, t_{1}$
$t_{1}=3\, s$
As per second condition,
$30 \,t_{2}=\frac{1}{2} \times 10 \,t_{2}^{2}=t_{2}=6\, s$
$\therefore t_{2}-t_{1}=3\, s$