1J40.10 Torque Bar




A weight is fixed at various distances from a handle. As the weight is moved along the bar, the work it takes to pivot the bar upwards about the handle changes noticably.



  • [1] 1 meter long aluminum bar with a handle
  • [2] 500 gram weight
  • (Optional) [1] Spring scale
  • (Optional) [1] Lab stand

Classroom Assembly

  1. Place 2 sliding weights near the handle.


  1. Get a strong-looking student volunteer to hold the grip bar.
  2. Starting with the weights positioned near the handle, the volunteer should attempt to rotate the metal rod so that it is horizontal.
  3. Move the weights further away from the handle.
  4. Ask the volunteer to rotate the metal rod so that it is horizontal. The volunteer should eventually fail with the weights furthest from the handle.


  1. Hang the spring scale from the lab stand.
  2. Attach the handle of the bar to the spring scale.
  3. Slide the weights back and forth to show the force registered by the scale. Note that the weights cannot be slid far along the bar before the scale registers the maximum reading of 100 N.


Additional Resources


  • PIRA 1J40.10
  • Video Encyclopedia 04-10 
  • Meiners 14-3.1; DHP Mo-5; DaR M-614


  • Don't attempt this at home!

Last revised

  • 2018


  • The weight of bar is approximately 5 N
  • The weight of bar and lower scale is approximately 9 N
  • The weight of bar, lower scale and 1 kg weight is approximately 19 N
  • Original construction: the bar was made from a 1 meter length of 1/2" diameter aluminum rod. The handle is a 6" length of 1.5" diameter aluminum tubing attached at right angles to the rod at one end.

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If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.