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Main » Optional Unit V - Kinematics & Dynamics » Momentum » Online Activity V.1.1

### Elastic & Inelastic Collisions - Online Activity V.1.1

Click on the "Java Cup" to start the applet. This Java applet deals with the extreme cases of a collision process illustrated by two wagons: For an elastic collision it is characteristic that the sum of the kinetic energies of the involved bodies is constant. After a perfectly inelastic collision, however, both bodies have the same velocity; the sum of their kinetic energies is reduced, compared with the initial value, because a part of it has changed into internal energy (warming up).

The total momentum of the involved bodies is conserved, regardless whether the collision is elastic or inelastic. The movement of the common center of gravity (indicated by a yellow dot) is not influenced by the collision process.

You can choose the simulation of an elastic or an inelastic collision by using the appropriate radio button on the top right. The "Reset" button brings the wagons to their initial positions; the animation is started by a mouse click on the "Start" button. If you select the option "Slow motion", the movement will be ten times slower.

You can write the values of mass and initial velocity into the textfields. Positive (negative) values of velocity mean a motion to the right (left) side. Extreme inputs are automatically changed.

Dependent on the selected radio button (on the bottom right), the applet will illustrate the velocities, the momenta or the kinetic energies of the wagons.

Collision Questions:

Try each of the simulations using the Java Applet. Work out the questions mathematically to confirm the Applet's calculations.

Part 1: Simulation of an Elastic Collision:

1. Run the elastic collision simulation. Run 3 - 5 trials changeing the mass [Max 1 kg] for Cart 1 OR Cart 2 and keep velocity constant. Run 3 - 5 trials changeing the velocity [Max 0.5 m/s] for Cart 1 OR Cart 2 and keep mass constant. Fill out the following table:
 Elastic Collisions Mass Velocity Momentum Trial: Cart 1 Cart 2 Cart 1 Cart 2 Cart 1 Cart 2 1. Before: After: 2. Before: After: 3. Before: After:

Do you see a trend from the data? Explain.
2. If the red wagon has a mass of 1.0 kg and a speed of 0.2 m/s at what speed should the blue wagon with a mass of 0.2 kg be traveling to stop the motion of the red wagon? What is the resultant speed of the blue wagon after the collision?
3. If the mass of the blue wagon is 0.8 kg and is traveling at -0.5 m/s how much change in momentum does the red wagon which is 0.4 kg and is traveling at - 0.1 m/s undergo after the collision?
Part 2: Simulation of an Inelastic Collision:
1. Run the inelastic collision simulation. Run 3 - 5 trials changeing the mass [Max 1 kg] for Cart 1 OR Cart 2 and keep velocity constant. Run 3 - 5 trials changeing the velocity [Max 0.5 m/s] for Cart 1 OR Cart 2 and keep mass constant. Fill out the following table: Fill out the following table:
 Inelastic Collisions Mass Velocity Momentum Trial: Cart 1 Cart 2 Cart 1 Cart 2 Cart 1 & Cart 2 1. Before: After: 2. Before: After: 3. Before: After:
Do you see a trend from the data? Explain.
2. What is the velocity of each wagon after the collision if the red wagon (0.6 kg) is double the mass of the blue wagon and the blue wagon is traveling at 0.5 m/s and the red wagon traveling at 0.2 m/s? Determine if the Law of Conservation of Momentum applies to this collision and prove with calculations.