Question

A $3\text{kg}$ ball strikes a heavy rigid wall with a speed of $10\text{m/s}$ at an angle of ${60}^{\circ }$. It gets reflected with the same speed and angle as shown here. If the ball is in contact with the wall for $0.20s$, what is the average force exerted on the ball by the wall ?

• A. $150N$
• B. $0$
• C. $150\sqrt{3}N$
• D. $300N$

Answer 1

The correct option is C $150\sqrt{3}N$

Change in momentum along the wall $={\text{mv cos60}}^{\circ }-{\text{mv cos60}}^{\circ }=0$

Change in the momentum perpendicular to the wall

$={\text{mv sin60}}^{\circ }-(-{\text{mv sin60}}^{\circ })=2{\text{mv sin60}}^{\circ }$

$\therefore$ Applied force

$=\frac{\text{Change in momentum}}{\text{Time}}$

$=\frac{2{\text{mv sin60}}^{\circ }}{0.20}$

$=\frac{2\times 3\times 10\times \sqrt{3}}{2\times 0.20}=50\times 3\sqrt{3}$

$=150\sqrt{3}N$.