A hailstorm causes an average pressure of 1.4 N/m² on the 200-m² flat roof of a house.The hailstones,each of mass 7.0 $\times$ 10^-3 kg,have an average velocity of 10 m/s perpendicular to the roof and rebound after hitting the roof with the same speed.How many hailstones hit the roof each second? A)4000 B)2000 C)1000 D)10 E)800

Question

Quizplus · Accepted Answer

The force exerted by the hailstones is equal to the change in momentum per second. The pressure is force per unit area, so the total force is 1.4 N/m² * 200 m² = 280 N. The change in momentum for each hailstone is 2 * mass * velocity = 2 * 7.0 * 10^-3 kg * 10 m/s = 0.14 kg*m/s. The number of hailstones per second is force/change in momentum per hailstone = 280 N / 0.14 kg*m/s = 2000 hailstones per second.

A Hailstorm Causes an Average Pressure of 1 ×\times× 10-3 Kg,have an Average Velocity of 10 M/s Perpendicular to the 200-M2

A Hailstorm Causes an Average Pressure of 1 $\times$ 10^-3 Kg,have an Average Velocity of 10 M/s Perpendicular to the 200-M²