# Force of impact, in newtons

1. Aug 27, 2009

### Mike123mike

I have a scenario which is simply a ball hits the ground from above i know the mass of the ball and the speed in mph of the ball just before it hits the ground. No other variables are known, I need to know the force it hits the ground.

What is the best way to calculate it? I had thought F = m x a, but to calculate the acceleration I would need a distance?

Obviously I'm not a physics person and any help would be greatly appreciated.

2. Aug 27, 2009

### dave_baksh

You also need to know the length of time that the ball is in contact with the ground. The formula for the force exerted is:

Force = (mass of the ball) x (speed of the ball)/(time the ball is in contact with the ground)

In order that the force is measured in Newtons you must use the following units:

mass: kilograms
speed: metres/second
time: seconds

Last edited: Aug 27, 2009
3. Aug 27, 2009

### Mike123mike

Thanks for that dave I don't suppose you can assist in calculating the time it is in contact with the ground as I suppose that time would vary depending on the speed too?

4. Aug 27, 2009

### xxChrisxx

Impacts are tricky to just guess at. You'd have to make an educated guesstimate bases on Coefficient of restiution, deformation of ball and ground.

Even then you are only coming up with a very rough average to the impact event.