Menu

Physics Tutorial 6.9 - Torque Revision Notes

Please provide a rating, it takes seconds and helps us to keep this resource free for all to use

[ 1 Votes ]

In addition to the revision notes for Torque on this page, you can also access the following Centre of Mass and Linear Momentum learning resources for Torque

Centre of Mass and Linear Momentum Learning Material
Tutorial IDTitleTutorialVideo
Tutorial
Revision
Notes
Revision
Questions
6.2Torque


In these revision notes for Torque, we cover the following key points:

  • What is torque?
  • Where does torque change from the moment of force?
  • How torque is calculated?
  • What is the positive direction of torque?

Torque Revision Notes

By definition, "Torque is a non-zero resultant moment of force usually produced by a single force or a couple of forces that help each other when trying to rotate a system around a fixed point."

Torque can be either produced by a single force of by a couple of forces as long as they are able to create rotation in the system. The meaning of torque is very close to that of moment of force. The most important difference between these two concepts lies in the fact that torque is a movement effect whereas moment of force is a static effect. This means torque is used where there is rotation involved whereas moment of force is used where there is no rotation (when there is equilibrium).

Examples of torque involving a couple of forces include:

  1. Rotating the steering wheel of a car,
  2. Rotating the handle bar of a bike,
  3. Two men rotating a grinding mill, etc.

Other examples of torque but which involve the use of a single force include:

  1. Pushing a door as it swings on its hinges when pushed,
  2. Turning the key,
  3. Turning the dood knob, etc.

Both Moment of Force and Torque have the same unit i.e. N-m but The equation of torque for a single force applied is:

τ = r × F

where r is the distance from the turning point (usually the radius of a circle), and F is the perpendicular force to the bar (line of action) or the tangent force used at that specific point of the circle.

The scalar equivalent of the above equation is

|τ| = |r| × |F| × sin θ

where θ is the angle between the axis of rotation and the force applied.

As for the torque of a couple, we obtain the following equation:

τ tot = r 1 × F 1 + r 2 × F 2

When the couple of forces is used to rotate a kind of wheel (such as a steering wheel), we have r1 = r2 = r

As for the signs of the directions of rotation, anticlockwise is taken as positive [clockwise is negative].

Whats next?

Enjoy the "Torque" revision notes? People who liked the "Torque" revision notes found the following resources useful:

  1. Revision Notes Feedback. Helps other - Leave a rating for this revision notes (see below)
  2. Centre of Mass and Linear Momentum Physics tutorial: Torque. Read the Torque physics tutorial and build your physics knowledge of Centre of Mass and Linear Momentum
  3. Centre of Mass and Linear Momentum Practice Questions: Torque. Test and improve your knowledge of Torque with example questins and answers
  4. Check your calculations for Centre of Mass and Linear Momentum questions with our excellent Centre of Mass and Linear Momentum calculators which contain full equations and calculations clearly displayed line by line. See the Centre of Mass and Linear Momentum Calculators by iCalculator™ below.
  5. Continuing learning centre of mass and linear momentum - read our next physics tutorial: Centre of Mass. Types of Equilibrium

Help others Learning Physics just like you

Please provide a rating, it takes seconds and helps us to keep this resource free for all to use

[ 1 Votes ]

We hope you found this Physics tutorial "Torque" useful. If you did it would be great if you could spare the time to rate this physics tutorial (simply click on the number of stars that match your assessment of this physics learning aide) and/or share on social media, this helps us identify popular tutorials and calculators and expand our free learning resources to support our users around the world have free access to expand their knowledge of physics and other disciplines.

Centre of Mass and Linear Momentum Calculators by iCalculator™