# Pressure of falling sand

• JSmith123
In summary, the conversation discusses the calculation of pressure exerted by falling grains of sand on a sticky surface. The solution involves finding the force due to one grain and multiplying it by the total number of grains, then dividing by the surface area. It is noted that the area can be 1m^2 or 1cm^2 to find the force.

## Homework Statement

Grains of sand of mass 3.10 10-3 g each, fall from a height of 0.8 m on a sticky surface at a rate of 50 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
F=ma=mv d/dt

## The Attempt at a Solution

So I understand I have to calculate the velocity and multiply that by the mass and number of grains. What I don't understand is the area. What is the area? Any help would be great.

use F = dP/dt to find force due to 1 grain ... multiply with total number of grains ... and then divide the area on which this total force is acting ... you get pressure

cupid.callin said:
use F = dP/dt to find force due to 1 grain ... multiply with total number of grains ... and then divide the area on which this total force is acting ... you get pressure

I see, but what is the area?

from P = F/A you can see that P=F when area is 1m^2

and you can also find force in 1cm^2

so its easy to find force in 1m^2 also, right?

Oh jeez the area is just 1m^2? I can't believe I didn't notice that. Anyways, thanks for the help.