Question

A body of mass $1kg$ crosses a point $O$ with a velocity $60m{s}^{-1}$. A force of $10N$ directed towards $O$ begins to act on it. It will again cross $O$ in

• A. 24 s
• B. 12 s
• C. 6 s
• D. will never return to O

Answer 1

Answer: (B)

From Newtons second law $F=ma$
$\Rightarrow$ $a=\frac{F}{m}=\frac{10}{1}m/s^2$
Since, the body returns to the point $O$ under a force, its displacement is zero. From equation of motion, we have
$s=ut+\frac{1}{2}a{t}^2$
$0=60t-\frac{1}{2}\times 10\times t^2$
$\Rightarrow t=12s$