Lab Spring Carts
In this lab you will investigate the distinction between external and internal impulses as well as conservation of energy in an elastic explosion.

Each group will need the following equipment:

• 2 meter sticks
• 1 triple beam balance
• 1 spring cart
• 1 companion cart

Before you begin the experiment you must measure and record the following data:

 mass of the spring cart (in kg)

 mass of its companion cart (in kg)

Part I: External Forces

In this phase of the experiment you will experiment with impulses on individual carts.

Initially, load the spring in the spring cart to its third, most compressed position. Place the cart against the wall and then use the metal rod to release the spring. Measure and record the perpendicular distance the spring cart rolls until it stops. Average your results.

In the next three trials, place the back of the spring cart against the wall with its companion cart against its compressed spring but this time you must hold the spring cart completely at rest. Once again, use the metal rod to release the spring. Measure and record the perpendicular distance the companion cart rolls until it stops. Average your results.

In this experiment we are considering the wall to be an "immovable object." Consequently, in each trial, all of the energy stored in the spring is delivered to the cart and all of the momentum of the system is in the cart.

 cart trial 1 trial 2 trial 3 average description (cm) (cm) (cm) (m)
 spring cart
 companion cart

Part II: Internal Forces

Now move to a position in the center of the hall and position the spring cart and its companion cart end-to-end with the compressed spring between them.

By using the metal rod to release the spring, measure and record the perpendicular distance that each cart rolls as it comes to a stop.

In this section, the energy stored in the spring is shared between the two carts as is the momentum of the system.

 cart trial 1 trial 2 trial 3 average description (cm) (cm) (cm) (m)
 spring cart
 companion cart
 Analysis   When you have completed your trials, open the EXCEL sheet titled 1-SpringCarts.xls and fill in the cells that are highlighted in light green. Do NOT touch the cells that are highlighted in light yellow since they are pre-programmed to assist you in the analysis of your data. Save your file to your period folder as LastnameLastnameSpringCarts.xls. Be careful that your data is in the requested unit of measure.