Question

A gun which fires small ball of mass $20g$ is firing $20$ balls per second on the smooth horizontal table surface ABCD. If the collision is perfectly elastic and ball are striking at the centre of the table with a speed $5m/s$ at an angle of ${60}^o$ with the vertical just before collision, then force exerted by one of the legs on ground is (assume total weight of the table is $0.2kg$)

• A. $0.5N$
• B. $1N$
• C. $0.25N$
• D. $0.75N$

Answer 1

Answer: (B)

$1N$

$f=\frac{dp}{dt}=\frac{d\left(mv\cos 0\right)}{dt}=(2\times 20\times 20\times {10}^3)\times (5\times \frac{1}{2})$

$=2N$

Force exerted by table wersht $=(0.2\times 10)$

$=2N$

Total force $=4N$

Force on each leg $=\frac{1}{4}\times 4=1N$