Question

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

(Assume total weight of the table is 0.2 kg)

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

Answer 1

The correct option is B 1 N

Total impulsive force imparted by the table to the balls is $nmg+2nm{v}_0\cos \frac{\pi }{3}=6N$.

4 times the force supported by each leg is equal to the weight of the table plus the impulsive force equals to $6.2N$. So the force exerted by one leg on the ground is $1.55N$.