Question

A small block B of mass 1 kg is placed on block A of mass 5 kg and length 20 cm as shown in figure. A constant horizontal force of 10 N is applied on block A. If all the surfaces are assumed frictionless and block B is at the right end of block A, then the time in which block B separates from A is

• A. $\sqrt{0.2}$s
• B. $\sqrt{0.5}$s
• C. $\sqrt{2}$s
• D. $\sqrt{3}$s

Answer 1

The correct option is A $\sqrt{0.2}$s

10N acts on the 5kg block.
The acceleration of the 5kg block is hence $a=\frac{F}{m}=2m{s}^{-2}$
Distance the 5kg block has to traverse before the smaller block falls is 20cm (0.2m).
using the equation of motion.
$s=ut+\frac{1}{2}a{t}^2$
$0.2=\frac{1}{2}\left(2\right)\left(t^2\right)$
$t=\sqrt{0.2}s$