cart rolling down a slope

A cart rolling down a hill certainly has energy which in turn affects its speed. But how does this speed change when you start the car off from a different point on the hill. And what has energy got to do with it? We decided to be scientific and investigate.

What we did

We let a car roll freely down a slope. We tried again, this time letting the car roll from different points further down the slope. Using Light gates linked to the computer, we measured the speed of a car at the bottom of a slope. Each time we recorded the distance the car rolled.

Our Results

This graph shows how the speed changes depending on where we let the car roll from on the slope.

You can do the questions below if you put your results into your data logging software.

• Looking at the results
• How is the speed of the car affected by its distance up the slope?
• Fit a function to the graph using a trial fit feature in your software. You should obtain an equation for the curve in the form y=.
• What is the value of b to the nearest integer? What does this tell you?
• What kind of energy depends on the distance of the car up the slope?
• What is the relationship between this energy and the distance up the slope?
• What kind of energy depends on the speed of the car?
• What is the relationship between this energy and the speed of the car?
• What conclusions can you draw about the energy of the car before it is released and its energy at the bottom of the slope?

Written up by Roger Frost, IT in Science and experiment by Martin King, formerly of Verulam School, Hertfordshire.