Question

A stone projected vertically up with a velocity of $10m{s}^{-1}$ reaches the highest point after $2$ s. If it is thrown with a velocity of $20m{s}^{-1}$, it reaches the highest point after a time of

• A. 2 s
• B. 4 s
• C. 6 s
• D. 1 s

Answer 1

Answer: (B)

4 s

At the highest point, $t\propto u$
$\Rightarrow \frac{t_1}{t_2}=\frac{u_1}{u_2}\Rightarrow t_2=t_1\frac{u_2}{u_1}$
$\Rightarrow t_2=2\times \frac{20}{10}=4sec$