In order to make an object turn in a circular path, we would have to apply a force. As a result the object may speed up rotationally. What we say is we are increasing the angular velocity and therefore there is also an angular acceleration. However, it's not just the strength of the force that determines the angular acceleration. The placement of that force with respect to the centre also determines the amount of angular acceleration.
You know this when using a wrench/spanner. The further your hand is along the handle, away from the turning point, the greater the effectiveness of loosening or tightening a bolt.
First, the force needs to be applied at a tangent to the circle. In other words, it must be acting perpendicular to the radius of that circle. (Or at least a component must be perpendicular).
Second, the distance from the centre the force is applied affects the angular acceleration. In other words, the radius of rotation
We now can introduce the idea of torque.
Torque is the rotational equivalent to force, in a rotational situation. This video examines how it works.
Check your understanding
Sample Problem
We are now ready to try a sample problem
Below is a sample problem with a video that explain how to solve it. It is suggested you try the problem beforehand, as this actually aids understanding, even if you are unsure if you are correct.
We are now ready to try a sample problem
Below is a sample problem with a video that explain how to solve it. It is suggested you try the problem beforehand, as this actually aids understanding, even if you are unsure if you are correct.
Two people are pulling on a pulley that is aligned vertically. It has a diameter of 20 cm. One person is trying to turn it clockwise and is applying a force of 100 at an angle of 30° to the horizontal. The other person is applying a force of 120 N at an angle of 45°, to turn it anticlockwise. What is the net torque?
Interactive
A seesaw is a simple but effective way to examine torque
Two forces can be applied at either end of the seesaw and balancing is achieved when the torque is equal on either side of the fulcrum
The following interactive is very basic but may be useful to address torque
A seesaw is a simple but effective way to examine torque
Two forces can be applied at either end of the seesaw and balancing is achieved when the torque is equal on either side of the fulcrum
The following interactive is very basic but may be useful to address torque
Here is another interactive to consolidate your understanding of torque.
Here you apply two forces to the ruler and the animation determines the resultant torque.