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Ramp Race

Primary schoolPhysicsToy car rolling down a 1 m ramp; rolling resistance of the surface slows it on the ramp and on the floor

About this experiment

Which car will roll the furthest? Prop a ramp up on some books, let a toy car go, and measure how far it travels across the floor. A steeper ramp gives the car more speed, and a rough surface like carpet or a towel slows it down. Race two cars side by side, change one thing at a time to make it a fair test, and record every race in a results table.

Learning goals

  • Describe how the height of a ramp changes how far a car rolls
  • Compare how smooth and rough surfaces slow a moving car
  • Explain friction as a force that slows things down
  • Plan a fair test by changing only one thing at a time
  • Record results in a table and use them to answer a question

How to use it

  1. 1Race the two cars with the starting settings. Which surface lets the car roll further?
  2. 2Make both surfaces the same. Give car A more books than car B. What happens?
  3. 3Put car B on the towel with 1 book. Why does it not move at all? How many books does it need?
  4. 4Keep the books the same and try every surface for car B. Put the surfaces in order from smoothest to roughest.
  5. 5Look at your results table. Is it a fair test if you change the books and the surface at the same time?

The model

More height means more speed at the bottom of the ramp
Friction pulls against the movement and slows the car
For older pupils: distance on the floor for a ramp of length L, slope θ and rolling resistance μ

Assumptions

  • The ramp is 1 m long and each book is 5 cm thick. The same surface covers the ramp and the floor.
  • Each surface slows the car by a fixed share of its weight, from 4 % for wood to 24 % for sandpaper. Air resistance is ignored.
  • Heights are drawn three times taller than they really are so the books are easy to see. The floor ends after 6 m.

Try this in class

  1. Q1Why do you think the car rolls further on wood than on carpet?
  2. Q2What would happen if the ramp were very steep?
  3. Q3Name one thing you must keep the same to make the test fair.
  4. Q4Why do roads have a rough surface, and why are slides made smooth?
  5. Q5Why might two real cars on the same ramp not stop in exactly the same place?

Frequently asked questions

How do I run this in a real classroom?

Use a plank or a strong piece of card, a stack of books and a toy car. Tape different materials onto the floor at the bottom, release the car without pushing it, and measure with a tape measure. Repeat each test three times.

Why does the car not move on a rough surface with only one book?

Friction from the rough surface is bigger than the push from gravity down such a gentle slope, so the car stays still. Making the ramp steeper gives a bigger push down the slope.

What is a fair test?

A test where you change only one thing, such as the surface, and keep everything else the same: the same car, the same number of books and the same starting point. Then you know the change caused the difference.