This page is for those who learn best by reading or want extra work to learn Torque. Come and see me at any time to get your questions answered.



Sample problem and solution

Problems for you to try

Torque Concepts

  1. Torque = force times distance

F = the applied force perpendicular to the radius arm

d = the length of the radius arm (the distance from the center of rotation)

    1. Torque is the amount of twist applied to an object around a center point. OHMCH1-1
    2. Also called a moment of force or moment.
    3. The force is applied perpendicular to the radius or moment arm.
    4. Torque is measured in foot-pounds (ft-lbs) or newton-meters (N-M).
    5. A small force at a large distance from the center point applies the same torque to an object as a large force at a small distance from the center.
      1. To open a door, you can push real hard near the hinge or push lightly near the doorknob. Either way, you apply the same torque to the door.
      2. Classroom example -- take the 8' 2x4. In the hole 1' from one end, place the blade of a large screwdriver. Secure the screwdriver vertically in a vise with the 2x4 horizontal. Put a large person on the 1' side, a small person on 7' side. Have them both push against each other. Which one will be able to push the other backwards?
  1. Where can you use this concept?
    1. Opening a jar with a jar opener.
    2. Loosening stuck bolts with a cheater bar.
      1. Must be careful not to put too much force on a nut or bolt head or you might exceed the strength of the bolt material.
    3. Seesaw or any balance mechanism.
      1. For equilibrium, the sum of all of the torques equals zero.
      2. Equilibrium is called Steady State. That means that the forces are balanced and the net force on the system and therefore, the net torque in any particular direction is zero.
  2. Problem Solving
    1. Show the general equation first.
    2. Next show the equation with the proper subscripts and variables.
    3. Then, show the equation with any known values inserted.
    4. Algebraically manipulate the equation to find the unknown, shown as a subscripted variable.
    5. Calculate the value.


- Show subscripts.

- Show units.

- Don't leave out any steps.

Sample problem and solution

Pulley A is 2 inches in diameter. Pulley B is 6 inches in diameter. Pulley A and Pulley B are physically attached to each other. What force P must be applied to keep the pulley system from moving in either direction.

First step of the solution

Problems for you to try
Sorry, there ain't none

Last Updated on September 6, 1996 by Kenneth Conley