Skip to main content
Physics LibreTexts

21.2: Introduction

  • Page ID
  • Torque is force acting at a distance, tending to cause rotation around a point.  The point about which the object rotates, the pivot point, is called the fulcrum.  When force is applied perpendicular to a lever arm, the amount of torque depends on the perpendicular force (F) applied and the length of the lever arm (d) through which the force acts.  

    Figure \(\PageIndex{1}\)


    \[\tau = Fd \nonumber \]

    Weight Force:

    \[W = mg \nonumber \]

    The amount of torque on one side of a fulcrum is equal and opposite to the amount of torque on the other side of the fulcrum.  This can allow a see-saw to be balanced if the two people sit at the correct distances from the pivot point.

    Figure \(\PageIndex{2}\)

    \[\tau_1 = -\tau_2 \nonumber \]

    Although the torque on each side of the pivot point is equal, the amount of force on each side of the pivot can be very different. 

    Figure \(\PageIndex{3}\)

    Contributors and Attributions

    • Was this article helpful?