1. Apr 24, 2005

### fork

A tennis ball is dropped from a certain height onto the top pan of the balance measure?
A.Weight of the ball.
B.Impact force on the pan due to the ball.
C.Impulse on the pan due to the ball.

Actually, what is the difference between impact force and impluse, thanks.

2. Apr 24, 2005

### James R

The impulse of a force is the force multiplied by the time over which it is applied. If an impulse is applied to an object, the impulse is equal to the change in momentum of the object.

3. Apr 24, 2005

### Andrew Mason

Newton's second law can be stated in the following ways:

$$F = dp/dt = d(mv)/dt = mdv/dt = ma$$

Think of the tennis ball hitting the ground and coming to a complete stop. The force is:

$$F = dp/dt = \frac{0 - mv}{\Delta t}$$

The quantity:
$$F\Delta t = \Delta p = m\Delta v$$

is called the impulse: a force applied for a certain time interval. It is equal to the change in momentum of the mass to which the force is applied.