Question

10000 small balls, each weighing 1g strike one square centimetre of area per second with a velocity 100 m/s in a normal direction and rebound with the same velocity. The value of pressure on the surface will be

• A. $2\times {10}^{3}N/m^2$
• B. $2\times {10}^{5}N/m^2$
• C. ${10}^{7}N/m^2$
• D. $2\times {10}^{7}N/m^2$

Answer 1

The correct option is D $2\times {10}^{7}N/m^2$

$P=\frac{F}{A}=\frac{nmv--mv}{A}=\frac{2mnv}{A}$
$=\frac{2\times {10}^{-3}\times {10}^4\times {10}^2}{{10}^{-4}}=2\times {10}^{7}N/m^2$