A disc of mass $10 g$ is kept floating horizontally by throwing $10 m a r b l e s / s e c$ against it from below. If the mass of each marble is $5 g$ , calculate the velocity with which the marbles are striking the disc. (Assume that the marbles strike the disc normally and rebound downward with the same speed)

9.8 m / s

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98 m / s

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0.98 m / s

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.098 m / s

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Solution

The correct option is B $0.98 m / s$
Using the Newtons second law we get $\frac{d P}{d t} = F$
$2 m n V = M g$
$V = \frac{M g}{2 m n}$
$= \frac{10 \times 10^{- 3} \times 9.8}{2 \times 5 \times 10^{- 3} \times 10} = 0.98 m / s$

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A disc of mass 10g is kept floating horizontally by throwing 10 marbles/sec against it from below. If the mass of each marble is 5g, calculate the velocity with which the marbles are striking the disc. (Assume that the marbles strike the disc normally and rebound downward with the same speed)

The correct option is B 0.98m/sUsing the Newtons second law we get dPdt=F2mnV=MgV=Mg2mn=10×10−3×9.82×5×10−3×10=0.98m/s

The correct option is B $0.98 m / s$
Using the Newtons second law we get $\frac{d P}{d t} = F$
$2 m n V = M g$
$V = \frac{M g}{2 m n}$
$= \frac{10 \times 10^{- 3} \times 9.8}{2 \times 5 \times 10^{- 3} \times 10} = 0.98 m / s$