The law of conservation of momentum states that "If no outside forces act on a group of objects, the momentum of the whole group will never change." In this lab, this means that the sum of the momentum of vehicle 1 and vehicle 2 before the collision is equal to the sum of vehicle 1 and vehicle 2 after the collision.

The momentum of an object (in this case, a vehicle) is obtained by multiplying the mass of the object by its velocity. When two vehicles collide, the differences in their mass and velocity, as well as the type of collision, will determine the change in velocity after the collision. Velocity has a direction. For something moving in a straight line, one way to show it is moving in a certain direction is by using arrows. An arrow pointing to the right (→) indicates a positive velocity. An arrow pointing to the left (←) indicates a negative velocity. If the velocity is negative, the momentum also will be negative.

In this Virtual Lab you will compare the velocities and momentums of two vehicles before and after a collision by using experimental data from collision tests at an accident reconstruction center. You will apply the law of conservation of momentum to the data to calculate velocities and accelerations before and after the collision of two vehicles.

Objectives:

Predict, describe, and compare the speed and direction of motion of two vehicles after a collision under the following conditions:

• There is no friction.
• All collisions are elastic.
• The masses of the two vehicles may be the same or different.
• The speeds of the two vehicles may be the same or different.
• The direction of motion of the two vehicles before the collision may be the same or opposite.
  

Calculate the momentum of each vehicle before and after the collision.

Procedure:

1. Click the Video button. Watch the video about conservation of momentum. Write your observations in your Journal.

2. Click on the radio button showing images of vehicles under Vehicle 1 and Vehicle 2 to select the masses of your vehicles. Select the velocity of Vehicle 2 using the buttons directly under the mass-selection buttons.

3. Predict a speed for vehicle 1 and a speed for vehicle 2 by clicking the up and down arrows.

4. Predict a direction of motion for vehicle 1 and for vehicle 2 by clicking the up and down arrows.

5. Click the Run Collision Test button to test your predictions. To see a replay of the collision, click the button again.

6. Open the Table and record the data.

7. Repeat this process until you have collected data for two collisions.

8. Verify the law of conservation of momentum by using the data you obtained and applying the following formula:
momentum before = momentum after

9. Open the Journal and complete the Journal questions.