Can you make something roll uphill?

Can you make something roll uphill?

Defy gravity!

What you need:

  • Plastic beaker (must be a cylinder). You can use any other kind of lightweight cylinder.
  • Elastic bands
  • Plasticine or Play-Doh
  • Books
  • Plastic tray (or something else to make a ramp with)

How to:

  1. Wrap some elastic bands around the beaker. This will give it some grip on the ramp.
  2. Build a ramp. Put one end of the tray (or whatever else you're using) on the ground. Rest the other end on a stack of books.
  3. Roll a worm of plasticine or Play-Doh so that it's the same length as your beaker. Stick it along one side of your beaker.
  4. Put the beaker on the ramp with the plasticine or Play-Doh on top.
  5. Roll the beaker slightly towards you (the top of the ramp), without letting go of it.
  6. Let go of the beaker.

Did you see the beaker roll upwards until the plasticine is at the bottom of the beaker? You might need to adjust the steepness of the ramp to get this experiment to work.

To see pictures of the experiment, go to CSIRO.

What's happening?

The beaker seems to be defying the laws of gravity by rolling up the ramp. Could Newton be wrong?

Mass and gravity work together to give an object a centre of gravity. This is the point that an object would balance on.

If the beaker is empty, its centre of gravity is in the empty space at the centre of the beaker. If you place the beaker on the ramp, gravity would pull on the beaker and the beaker would roll to the floor.

The plasticine or Play-Doh changes the beaker's centre of gravity to where the plasticine is. Although the beaker rolls up the tray, the centre of gravity actually moves down the ramp. Newton's laws of gravity are still correct!

Curriculum information