# Calculate the force experienced by a fixed surface

1. May 7, 2007

### jainabhs

Hi,
Can anyone tell me is there any way to calculate the force experienced by a fixed surface when hit by an object(of x mass) at say y height from the surface and accelerating towards it with 10m/s-sq?
Is this force dependent on the surface(which i suppose yes but just for clarifaication)? If yes then please given an example of one such surface and the means to calculate the force.

2. May 7, 2007

### lpfr

Begin with an elastic surface as a trampoline. When the object arrives at the surface, it deforms it and the surface exerts a force on the object that brakes it. The surface continues to deform and to brake the object until the object stops. At this moment all the kinetic energy of the object has transformed in potential energy of the deformed surface. If the force exerted by the surface is proportional to the deformation F=kx. At the moment of stop the energy will be E=1/2 kx^2.
If the surface is not elastic, the mathematical from of the force is different and depends on the surface material and geometry. But the surface exerts a force on the object until it stops. No calculations can be made without knowing exactly the force exerted by the surface.
If the surface is partially elastic, same thing: you must know the behavior of the force as the surface deforms.
The dependence of the force with deformation can be any thing. There is no way to make a general calculation. Well, you can, but the result is just an integral that you cant evaluate without the knowledge of the surface.

3. May 7, 2007

### Weimin

You can calculate the force if you know

1. the velocities of the object right before and after the collision and

2. the duration time of the collision

Then you will follow the formula F= change of momentum divided by time