Turning effects and a clock-spring

Demonstration

Springs tend to return to their original shapes when they are stretched, compressed, or, in this case, turned.

Apparatus and Materials

• Clock-spring, large, mounted on a board at the spring centre
• Retort stand, boss, and clamp
• Loads to be hung from spring arm, e.g. thread

Health & Safety and Technical Notes

Read our standard health & safety guidance

If loads slip along the arm of the spring, use small pieces of modelling wax or Plasticine to hold them steady.

Procedure

1. Clamp the board vertically to a retort stand, for convenience of demonstration.
2. Hang loads from the arm of the spring to apply force to it. The spring tends to return to its original shape, and provides a force which opposes the applied force.
3. Hang different loads at the same place on the arm, to show that weight is a factor in the size of the turning effect due to the load.
4. Hang a load at different positions along the arm, to show that distance is a factor in the size of the turning effect due to the load.

Teaching Notes

• The force due to a spring, in opposition to an applied force, is a restoring force.
• An additional demonstration could show a screw jack (or a rotating chair with a spiral thread), raising a load by pushing on the arm of the screw jack with a very small force. The longer the arm, then the smaller the force.

This experiment was safety-tested in October 2004