Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds

Turning effects and a clock-spring


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.



spring with arm

a Clamp the board vertically to a retort stand, for convenience of demonstration. 

b 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. 

c 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. 

d 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

1 The force due to a spring, in opposition to an applied force, is a 'restoring force'. 

2 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-checked in October 2004


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