Question

A body of mass $3\,kg$ hits a wall at an angle of $60^{\circ}$ and returns at the same angle. The impact time was $0.2\,\sec$. The force exerted on the wall

• A. $150\sqrt3 N$
• B. $50\sqrt3 N$
• C. $100\, N$
• D. $75\sqrt3 N$

Answer 1

Answer: (A)

Given,
Normal initial velocity, $v _{ i }=-10 \sin 60^{\circ}$
Normal final velocity, $v _{ f }=10 \sin 60^{\circ}$
Change in momentum, $\Delta P = m \left( v _{ f }- v _{ i }\right)$
$=3\left[10 \sin 60^{\circ}-\left(-10 \sin 60^{\circ}\right)\right]$
$=51.96 \,Ns ^{-1} $
Force, $F =\frac{\Delta P }{\Delta t }=\frac{51.96}{0.2}=150 \sqrt{3} N$
Hence, force is $150 \sqrt{3} N$