A metal base supports a ruler by its center allowing it to sway on its base. The ruler has two weight hangers that can be adjusted to any place on the ruler. The apparatus shows that the torque exerted by any force is equal to the force lever arm. A set of slotted weights is also provided.
A stepped wheel with different weights hanging at different radii maintains its equilibrium. The wheel is held by its center and is free to rotate. From each radius, there is a light string to hold the weights. It can be used to illustrate the basic relations between force and distance.
A large spool has a string wrapped around its inner drum. Place the spool on the floor or on top of the table. First let the string come out on top as you pull it. It will move in your direction. Next, turn the spool over and pull the string in the same direction. The spool will still move forward.
Ask the students which way the spool will rotate when the spring is pulled horizontally. It may surprise them that the spool still rolls towards the demonstrator.
Finally, it can be shown that it will continue to do so until the angle is reached where the line of action passes through the point of contact of the spool and table. The spool will slip forward if the line of action of the pull passes through the point of contact of the spool and the table.
The robotic arm can be used to demonstrate torque in an entertaining way. It is small enough to be easily handled, but large enough to be readily seen by the entire class. The arm can rotate about three different axes and its gripper can pick up reasonably sized objects.
Click here to see a video of the Robotic Arm demo.