# Pressure of Falling Sand

1. Feb 9, 2009

### dmark312

1. The problem statement, all variables and given/known data

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?

2. Relevant equations

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

3. The attempt at a solution
I don't know where to start. Anyone care to point me in the right direction?

2. Feb 9, 2009

### m.e.t.a.

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.

3. Feb 9, 2009

### Redbelly98

Staff Emeritus
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.