Question

10,000 small balls, each weighing 1 gm , strike one square cm 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 xx 10^(3)`Nm^(-2)`
B.
C. `2 xx 10^(5)` Nm^(-2)`
D. `10^(7) Nm^(-2)`

Answer 1

Correct Answer - D
In `1cm^(2)` are, `10^(4)` balls are striking per second. Therefore in `1m^(2)` are, `10^(8)` balls will strike per unit time.
Change in momentum of each ball per second will be 2mu
`therefore` Pressure = `F/A`=`(Deltap//Deltat)/A)`
`10^(8) xx 2 xx 10^(-3) xx 10 = 2 xx 10^(-7) Nm^(-2)`