# Impulse problem

1. Apr 28, 2008

### chocolatelover

1. The problem statement, all variables and given/known data
A ball of mass .110 kg is dropped from rest from a height of 1.25 m. It rebounds from the floor to reach a height of .800 m. What impulse was given to the ball by the floor?

2. Relevant equations

I=ΣFΔt
Δp=I

3. The attempt at a solution

Could someone please tell me if this is the correct formula?

Thank you very much

2. Apr 28, 2008

### Feldoh

Hi chocolatelover! Both of your equations look right but need some minor tweaking.

For starters (I have no clue why, but...) the symbol for impulse is a capitol J.

So J = Δp for instance.

Your first equation should be extended a bit more.

J = ΣFΔt would give you an approximation for impulse however if you wanted the exact value of J you would need to make Δt -> 0, and sum up an infinite number tiny bits force.

A more concrete definition would be $$J = \int_{t_i}^{t_f}{F dt}$$

3. Apr 28, 2008

### chocolatelover

Thank you very much

Does this look right?
integral from 1.25 to .800 (.110kg)(9.8m/s^2)dt

=.8624-1.35
=-.4876

Thank you very much