Question

A $1kg$ particle strikes a wall with velocity $1m/s$ at an angle of ${30}^o$ with the normal to the wall and reflects at the same angle. If it remains in contact with wall for $0.1s$, then the force is:

• A. $0$
• B. $10\sqrt{3}N$
• C. $30\sqrt{3}N$
• D. $40\sqrt{3}N$

Answer 1

The correct option is B $10\sqrt{3}N$

$\Delta P=2mu\cos {30}^o$
$=2\times 1\times 1\times \frac{\sqrt{3}}{2}=\sqrt{3}kgm/s$
$F=\frac{\Delta P}{\Delta t}=\frac{\sqrt{3}}{0.1}=10\sqrt{3}N$