Impulse and Momentum Lab
Name: ___________________________________
Period: _____________
Impulse: Impulse is defined to be force times time: I = Ft
Momentum is defined as the mass time velocity: p = mv
The Impulse Momentum Law states that the impulse is equal to the change in momentum: Ft = mΔv
If a ball is dropped from a height, Y, you can find the impact velocity and rebound velocity using the 3 kinematic
equations (amigos). Make sure you have the correct signs on the velocities or you won’t get correct answers.
The impact velocity is the velocity of the object right before it hits. Here, that means it is the final velocity of the
falling ball right before it hits the ground. (Your initial velocity is zero, since the ball is being dropped, and your
acceleration is due to gravity)
The rebound velocity is the velocity with which the ball comes off of the ground after the collision. To find this,
use the height of the ball’s bounce, set the vf = 0, and find vi. (Again your acceleration is still gravity)
So, the change in momentum is: Δp= m(vrebound – vimpact)
Assume the force applied during the impact is equal to the weight of the ball (Fg=mg). (This is not entirely true –
but a close enough approximation for today)
Purpose: What is the Purpose of the lab?
Initial Height
Mass of ball (kg)
vimpact
Rebound Height
vrebound
Initial Momentum
Final Momentum
Δp
Impulse
Force
Time of Impact
Trial 1
Trial 2
Trial 3
Trial 4
0.5 m
1.0 m
1.5 m
2.0 m
Calculations (show your work completely for at least one trial – include calculations for v impact, v rebound,
initial momentum, final momentum, Δp, impulse, force, and time of impact ):
1.
If you changed the type of ball you used (rubber to tennis, or tennis to rubber) what do you think would
have happened to your impulse values? Why would this be the case?
2.
Were you initial and final momentum the same? Explain why they were or were not the same.
3.
What is conservation of momentum and list the two different equations for conservation of momentum.
4.
Is the collision between the ball and the floor inelastic or elastic? Why?