ERHS Physics

Conservation of Energy Lab
The Law of Conservation of Energy proclaims that the energy in the Universe is constant. Your text gives numerous examples and sample problems wherein Potential Energy that is lost by an object is transferred into Kinetic Energy. In this activity we will explore this concept.
You will use a specially prepared dynamics cart that has a straight metal "vane" attached to it. The vane is exactly 10.0 cm. in length, and the cart's mass is exactly 1.012 kg.

The cart will roll down a ramp. As the vane passes through the photogate timer at the bottom of the ramp, the timer will note exactly how long the 10 cm takes to pass. From this information, velocity of the cart can be determined precisely. Watch the video clip below to get the general idea:
You will use a battery powered photogate timer, and a dynamics cart in this lab.
The two views here (left and right) show the basic apparatus setup. Note the positioning of the photogate over the finish line.
The gate must be set up directly over the line, and adjusted so that the vane on the cart will not strike it as it passes through.
Make sure the photogate is on and properly set. Have one lab partner release the cart from the starting line at the top of the ramp without giving it any impulse.

Someone needs to be at the bottom of the ramp to capture the cart at the end of its run. The cart should be captured in a cardboard box to avoid injury.

Note the time required for the vane to pass through the photogate. GRAPH your times vs ramp height to look for patterns and help detect suspect data.

Measure the difference in height between the starting and finish points.

Compute the potential energy of the cart at the starting line with respect to the finish line. See this page to see how to take the two measurements you will need.

Report the percent of the potential energy that is expressed as kinetic energy at the finish line! Repeat the experiment with a trial at each of the eight possible ramp heights.