Angular Velocity
Forces and Motion

Key Drop

Enrichment Activity for 5-11 11-14

What you need

  • A bunch of about 3 keys
  • A large paperclip or washer
  • A pencil
  • 1m of string


  1. Tie the bunch of keys to one end of the string and the paperclip to the other
  2. Place the string over the pencil so that the keys hang down a couple of centimetres
  3. Hold the paperclip horizontally out to the other side
  4. Let go of the paperclip

Results and Explanation

The paperclip winds around the pencil and stops the keys hitting the floor!
This is because the keys pull the paperclip towards the pencil, but gravity is also pulling it downwards so it moves in a circle. As the paperclip gets closer to the pencil, its angular velocity increases, and it wraps around the pencil.

These experiments have not been specifically safety tested for home use but we believe them to be safe if the instructions are followed. Adult supervision or direction is recommended as appropriate. All experiments are carried out at your own risk.

Angular Velocity
is a special case of Velocity
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