Physics 105

April 7, 2003

Today we will look at the physics behind rocket propulsion:

total linear momentum before the explosion = total linear momentum after the explosion

We will use the same setup we used in experiment P17 to study collisions. Our goal is to verify that linear momentum is conserved in explosions, and estimate the energy released in an explosion.

We will simulate explosions by taking two carts, with the plunger compressed between them. The system is put at rest between the two photogates which will be used to measure the velocity of the carts after the "explosion". Note that once again we have to take friction into consideration and we might possibly need to make the same changes to the experiment we made last week on Monday.

Obviously the initial linear momentum is equal to zero since the system is at rest. Carry out a number of experiments to address the following questions:

• Is linear momentum conserved in our explosions?
  • Make sure you estimate your errors, and you repeat the measurements with different masses.
• How much energy is released in your explosions, and how is this energy shared between the two carts (e.g. does each cart take away 50% of the energy released, or is this ratio affected by the masses of the carts)?
• What is the relation between the energy released and the compression of the plunger (use various compression distances)?