# Pendulum Impact Force Calculation

1. Oct 22, 2009

### mh5594

Hi,

I am performing a set of tests using a pendulum. The test involves a pendulum of length 0.55metres, the weight of the entire pendulum is 2kilos.

The test involves letting the pendulum go from a set height and calculating the force when it impacts an object held in a vice at the bottom of the arc.

Force values need to be calculated for releasing the pendulum at 5 through to 45 degrees in 5 degrees incremements and with the weight of the pendulum changing from 1, 1.5, 2, 3kilos respectively.

I have spent a number of hours trying to work it out however the formula I am using are not producing sensible results. Please could any of you help me with the necessary formula that I will need to perform the calculations.

Cheers,
Michael.

2. Oct 22, 2009

### Troels

Force is bad choice here, because the force depend on the time the impact takes (which can be very short indeed).

You'd be much better off with momentum; you would want to calculate the momentum of the pendulum, right before the impact, and then apply conservation of momentum, which does give you the subsequent motion of the impacted object (under suitable constraints). If you then really need the force, you can get it from Newtons 2nd Law:

$$\vec F=\frac{\Delta \vec p}{\Delta t}$$

where $$\Delta \vec p$$ is the change in momentum of one of the bodies.

Last edited: Oct 22, 2009