NAME __________________________________________________CLASS_____________DATE____________
Collision Lab: Conservation of Linear Momentum
Background
When objects collide, whether shopping carts, automobiles or Dynamics Carts, the results can be
complicated. Yet even in the most chaotic of collisions, as long as there are no external forces
acting on the colliding objects, one principle always holds and provides an excellent tool for
understanding the dynamics of the collision. That principle is called the conservation of
momentum. For a two-object collision, momentum conservation is easily stated mathematically
by the equation: m1v1 + m2v2 = m1v1 + m2v2 If external forces such as friction are ignored, the
sum of the momenta of the moving objects before the collision is the same as the sum of the
momenta after the collision. But kinetic energy may or may not be conserved in a collision; it
depends on whether it was an elastic or inelastic collision.
For You To Do
Use a Motion Sensor to measure the motion of a Dynamic Cart before and after it has a collision
with a wall. Use DataStudio to: (1) plot and analyze the cart’s position, velocity, and acceleration
before and after the collision and (2) determine the momentum and kinetic energy of the cart
before and after the collision. Compare the momentum and kinetic energy before and after the
collision.
Equipment Needed
Dynamics cart
Pasco setup
Motion sensor
Balance
DataStudio P04: Motion Graphs
Part I: Computer Setup
1. Set up computer/interface system
2. Connect Motion Sensor into Digital Channel 1 (yellow) and Channel 2 (black)
3. Open Activity DataStudio P04: Motion Graphs
4. Lab opens with Graph of position, velocity and acceleration
Part II: Sensor Calibration and Equipment Setup
1. You do not need to calibrate the Motion Sensor.
2. Place Motion Sensor on Table opposite site for collision. Place Dynamics Cart about 15 cm
in front of Motion Sensor with spring plunger facing wall as shown below.
Dynamic Cart
Wall
Part III: Data Recording
1. Place hand on Dynamics Cart.
2. Start recording data
3. Give the cart a slight push. Remove hand quickly.
4. Stop cart when it has bounced back with your hand before it hits Motion Sensor.
5. Stop recording data.
6. Print Graphs and save as Collision Lab on jumpdrive.
Motion
Sensor
NAME __________________________________________________CLASS_____________DATE____________
Analyzing the Data
1. Interpretation of Graphs
a. Use the Position-Time graph to explain the cart’s motion (position) before, during
and after the collision. Identify these areas on the graph.
b. Use the Velocity-Time graph to explain the cart’s motion (velocity) before, during
and after the collision. Identify these areas on the graph.
c. Use the Acceleration-Time graph to explain the cart’s motion (acceleration) before,
during and after the collision. Identify these areas on the graph.
2. Analysis of Graphs
a. Use DataStudio to find the slope of the Position-Time graph before and after the
collision. Write these values on your Position-Time graph. What quantity does this
measure?
b. Find the slope of the Velocity-Time graph before, during and after the collision.
Write these values on your Velocity-Time graph. What quantity does this measure?
How do they compare to each other?
c. Find the maximum acceleration of the cart on the Acceleration-Time graph. Write the
value on your Acceleration-Time graph. How does it compare to the values you
received for the slope of the V-T graph during the collision?
3. Calculations
a. Calculate the momentum of the Dynamics Cart before and after the collision. Use the
velocity values from 2a.
b. Calculate the kinetic energy of the Dynamics Cart before and after the collision. Use
the velocity values from 2a.
Conclusion
1. How does the momentum of the cart before the collision compare to the momentum after the
collision? Is it conserved? Explain.
2. How does the kinetic energy of the cart before the collision compare to the kinetic energy
after the collision? Is it conserved? Explain.
3. Is the collision of the car with the wall elastic or inelastic? Explain how you know.
4. What are the three major sources of error in this lab? Suggests ways they can be reduced.