# Calculating Mass of Impacting Material

1. Jun 2, 2006

### j777

I'm trying to figure out if it is possible to accurately calculate the mass of a granular material (something like grain) impacting a very rigid object (a fixed metal plate) if the velocity of the granular material, impact force, and time of impact are known. After googling around a bit I've come up with the following formula:

m = (impact force * time of impact) / (velocity of granular material)

Am I on the right track or way out in left field? What are some of the important things to consider when trying to measure mass in this way?

Physics is not a strong-point of mine so any help would be greatly appreciated.

2. Jun 2, 2006

### H_man

Yes, I believe there are methods.

However I must ask. Is this a theoretical question or do you actually need to measure the mass of the grains.

The formula you quote looks right.

Impulse = Force*Time = Momentum

So on the top of your equation you have momentum which is equal to the Mass * Velocity.

You then divide by the velocity which should indeed give you the mass.

3. Jun 2, 2006

### j777

Yes, I'm interested in finding the mass of grain for flow metering purposes.

4. Jun 2, 2006

### H_man

My first thought on this matter would be that a pendulum should serve your needs adequately.

You can determine the momentum of the material impacting upon the pendulum from the angle at which it is displaced.

Many configurations of pendulum are possible. It all really depends on what your constraints are.

Perhaps even some kind of "grain-turbine" measuring an induced current could do the trick.

Anyway, let us know how it works out. Best of Luck!

5. Jun 2, 2006

### j777

Thank you for your thoughts. I will consider them as I continue to play around with this project.