# Impact Force

1. Jul 18, 2008

### Matt_B

First off, i dont know if this is the right section for this, just thought i would try though...

Here is my problem. I need a formula for impact force and duration when using spring pressure. I have the mass of the object in grams, the force of the spring, and the push length. Now i do understand that friction comes into play, but at this time i am not wanting to figure that it. Is there anyone that can help me on this one?

oh, i also have the spring pressure at the beginning of push, and the end of push, if that matters

Any other info you might need, let me know, i will try my best to provide it. :)

2. Jul 20, 2008

### Matt_B

Let me describe this a lil more.

Basically what i have is a captured spring that has a preload on it. Then i pull it back a little bit more and then release it. It does not extend past the original preload but it is launching an object and the object travels a little bit further before reaching impact. I really do not know how better to describe the situation.

Any help on this would be very appreciated. I have spent a while searching for information to help me solve this, and i have not been able to find anything. I thought i would give yall a shot :)

3. Jul 21, 2008

### runningman97

I don't quite understand the situation, you're firing the object with a spring right? Is this in the air like projectile motion and you want to know the time of flight and impact force with the ground?

4. Jul 21, 2008

### Matt_B

Think of it more like a pinball machine launch. Only say there is a wall that is .100" infront of the ball. Now how do you figure out the speed of the ball when it would impact that wall when you retract the spring and let it fly?

That is the best example i have.

5. Jul 21, 2008

### runningman97

Ok, well you would need to find the impulse exerted by the spring on the ball and use the fact that this is equal to the change in momentum of the ball. Over such a short distance friction wouldn't really come into play significantly.

Since you have the force at the beginning and end of the push i take it you have some information on the time taken for the push. The impulse can be estimated by the average force multiplied by this time. This would give you an estimate of the impact momentum and hence the speed. Hope that helps