Physic C....collision!!!!!!?

Question

a platform scale is calibrated to indicate the mass in kilograms of an object placed on it. Particles fall from a height of 3.5 m and collide with the platform of the scale. The collisions are elastic; the particles rebound upward with the same speed they had before hitting the pan. If each particle has a mass of 110 g and collisions occur at the rate 42 s^-1, what is the average scale reading?

Answer 1

m/t = .11 kg/p * 42p/s = 4.62 kg/sec

∆V = 2*√(2gh) = 16.565 m/s

F = (m/t)*∆V = 4.62*16.565 = 76.53 N

Since the scale is calibrated in kg,

Fs = F/g = 7.8 kg