Question

A dish of mass 10 g is kept floating horizontally in the air by firing bullets each of mass 5 g with the same velocity. If 10 bullets are fired per second and the bullets rebound with the same speed, then the velocity of each bullet is:

• A. 196 cm/sec
• B. 98 cm/sec
• C. 49 cm/sec
• D. None of these

Answer 1

Answer: (B)

98 cm/sec

Answer 2

weight of disc = force on disc due to bullets

Mg = 2mnv

v = $\frac{Mg}{2mn} = \frac{10^{- 2} \times 9.8}{2(5 \times 10^{- 3})(10)}$ = 0.98 m/s

or v = 98 cm/s