# Average acceleration

1. Jun 18, 2012

### nbroyle1

A 52.0-g Super Ball traveling at 28.0 m/s bounces off a brick wall and rebounds at 16.5 m/s. A high-speed camera records this event. If the ball is in contact with the wall for 3.60 ms, what is the magnitude of the average acceleration of the ball during this time interval?

Im not really sure what formula to use for this problem. I don't think the mass of the ball is relevant to the average acceleration but not sure. I know average acceleration is
v(final)-v(initial)/t(final)-t(initial)

2. Jun 18, 2012

### Staff: Mentor

That's the one you need. Hint: Velocity is a vector, so direction--and signs--matter.

3. Jun 18, 2012

### nbroyle1

ok i tried plugging into the equation is this correct 16.5-28/.0036? I converted the miliseconds to seconds for the denominator.

4. Jun 18, 2012

### Staff: Mentor

No. You made an error with signs. If the initial velocity is +28 m/s, what is the final velocity after the rebound?
Good.

5. Jun 18, 2012

### nbroyle1

Oh gotcha! ok thanks!!!