# Pressure of Falling Sand

## Homework Statement

Grains of sand of mass 2.90x10^-3 g each, fall from a height of 0.5 m on a sticky surface at a rate of 45 grains per second per cm^2. What pressure does this shower of sand exert on the surface, assuming that air resistance can be neglected?

p=F/A=mv^2(N/V)

## The Attempt at a Solution

I don't know where to start. Anyone care to point me in the right direction?

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You can work out the velocity with which every grain of sand lands. You also know what total mass of sand falls per second. Your force, $F$, is equal to the force required to accelerate that certain mass of sand by that certain velocity in one second.

Redbelly98
Staff Emeritus
Homework Helper
Welcome to PF

P = F / A is definitely useful here.

Also of use is

F = Δp / Δt

where little p is momentum (not pressure). You'll need to figure out the change in momentum, for the total of all grains of sand that hit a square cm of the surface, in 1 second.