Friction
Forces and Motion

Gripping Rice

Enrichment Activity for 5-11 11-14


What you need

  • Uncooked rice
  • A pencil
  • A large empty jar with a narrow neck

Instructions

  1. Fill the jar to the brim with uncooked rice (make sure you have a jar that narrows towards the top)
  2. Push the pencil right into the rice
  3. Stab the rice repeatedly, alternating between shallow and deep stabs. It could take up to 40 stabs, but you'll start to feel the pencil gripping the rice
  4. When you feel a firm grip, carefully lift the jar by the pencil

Results and Explanation

The pencil lifts the jar. As you push it in, the pencil forces the grains sideways, but they fall back into the gap as you try to pull it out. The rice becomes more and more tightly packed until the friction between the rice and the pencil is so great you can lift the jar.

Friction
is a special case of Force
IOP DOMAINS Physics CPD programme

New videos on forces

Our first collection of videos gives teachers and coaches of physics a preview of the training we offer ahead of this term's live support sessions.

Find out more