# Foo - Physics Lab Question

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View Full Version : Physics Lab Question

MattP.
12-02-07, 09:38 PM
Hey all.

In this lab, we select different types of balls (bouncy, tennis, ect.) and drop each from 1m, onto a hard surface, and record how high the first bounce is. Then we have to determine the velocity of the ball before it hit (neglecting air resistance), and after it hit, the total energy the ball had before and after it hit, the momentum it had before and after it hit, and the change in momentum.

Then I am asked to "determine the impulse that acted on the ball" Uhh, how?

Case in point: Bouncy Ball
Mass: .00856 kg
Momentum before collision: -.038 kg/m/s
Momentum after collision: .020 kg/m/s
Change in Momentum: .058 kg/m/s

How do you find the impulse that acted on the ball? If velocities are needed let me know.

Siu Blue Wind
12-02-07, 09:39 PM

He's the brains here.

p4nh4ndle
12-02-07, 09:48 PM
through change in momentum (impulse is defined as instantaneous change in momentum)

MattP.
12-02-07, 09:52 PM
through change in momentum (impulse is defined as instantaneous change in momentum)
So if the change in momentum is .058 kg/m/s the impulse that acted upon the ball would be .058 kg/m/s/?

BenLi
12-02-07, 09:53 PM
impulse is also delta F multiplied by t

p4nh4ndle
12-02-07, 10:01 PM
see http://scienceworld.wolfram.com/physics/Impulse.html as a ref

p4nh4ndle
12-02-07, 10:04 PM
So if the change in momentum is .058 kg/m/s the impulse that acted upon the ball would be .058 kg/m/s/?

yes. you can see that the units work (from BenLi's eq).
*edit* except it's Kgm/s not Kg/ms (or kg/m/s)

MattP.
12-02-07, 10:10 PM
yes. you can see that the units work (from BenLi's eq).
*edit* except it's Kgm/s not Kg/ms (or kg/m/s)

Excellent, appreciate everyone's help!