Question

$10,000$ small balls, each weighing $1g,$ strike one square cm of area per second with a velocity $100m{s}^{-1}$ 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

Answer: (A)

$2\times {10}^{3}N{m}^{-2}$

$\text{mass striking per second}=\mathrm{10000}\times {10}^{-3}\times A$

$=\mathrm{10kg}{S}^{-1}$

Force = Change in momentum per sec.

$=2\times 10\times A\times 100=\text{2000Akg}M{S}^{-2}$

Pressure $=2\times {10}^3{Nm}^{-2}$

Answer:-(A)