A disc of mass 10 g is kept floating horizontally in the air by firing bullets, each of mass 5 g , with the same velocity at the same rate of 10 bullets per second. The bullets rebound with the same speed in positive direction. The velocity of each bullet at the time of impact is (. textTake g=9.8 m s- 2.)

Question

A disc of mass 10 g is kept floating horizontally in the air by firing bullets, each of mass 5 g , with the same velocity at the same rate of 10 bullets per second. The bullets rebound with the same speed in positive direction. The velocity of each bullet at the time of impact is (. textTake g=9.8 m s- 2.) (A) 196 cm s- 1 (B) 98 cm s- 1 (C) 49 cm s- 1 (D) 392 cm s- 1

Tardigrade Admin · Accepted Answer

2mnv=Mg v=(M g/2 m n) ⇒ u =(10 × 980/2 × 5 × 10)cm s- 1 =(9800/100)cm s- 1 =98 cm s- 1

$196 c m s^{- 1}$

98 $c m s^{- 1}$

49 $c m s^{- 1}$

392 $c m s^{- 1}$

$2 mn v = M g$
$v = \frac{M g}{2 mn}$
$\Rightarrow u$ $= \frac{10 \times 980}{2 \times 5 \times 10} c m s^{- 1}$
$= \frac{9800}{100} c m s^{- 1}$
$= 98 c m s^{- 1}$

196cms−1

98 cms−1

49 cms−1

392 cms−1

2mnv=Mg v=2mnMg​ ⇒u =2×5×1010×980​cms−1 =1009800​cms−1 =98cms−1

$196 c m s^{- 1}$

98 $c m s^{- 1}$

49 $c m s^{- 1}$

392 $c m s^{- 1}$

$2 mn v = M g$
$v = \frac{M g}{2 mn}$
$\Rightarrow u$ $= \frac{10 \times 980}{2 \times 5 \times 10} c m s^{- 1}$
$= \frac{9800}{100} c m s^{- 1}$
$= 98 c m s^{- 1}$