Illustrates that the torque of gravity, acting on a stick hinged at its base to the table, causes the end of the stick to accelerate faster than g. (See Falling Chimney (Gravitational Acceleration) [1])
A bicycle wheel can be mounted on the lecture table so you can illustrate the effect on acceleration of exerting forces on it at various radii and in various directions. A crescent wrench is also supplied so you can illustrate how to produce the maximum torque on the nut holding the bicycle wheel. Another simple illustration of torque is to open the door to the lab at the front of the lecture hall and push on it at various radii from the hinge with your index finger. The crumpling of your finger indicates the larger forces needed at the smaller radii.
A more quantitative demonstration of torque uses the rotational acceleration device shown here [2]. The spindle is fitted with a spool of twice the radius of the shaft so the falling weight acts at 2R. Two devices are available. Adjust the weights so the rotational inertia is the same, and compare the rotational acceleration of the devices with the falling weight acting at R and 2R.
Add hanging weights at different distances to break the hold of the friction nut. It takes twice the weight at half the distance. Watch out for your foot.
Hold a meter stick at two arbitrary places with your two index fingers. When you bring your index fingers together, they will meet at the center of the meter stick. You can show that this is a consequence of the two different friction forces resulting from the different torques exerted by your fingers. Amazingly, even if the coefficients of friction are very different, say by covering one finger with slippery chalk dust and the other with a sticky rubber glove, your fingers will still meet at the center. If a weight is placed on one end of the meter stick, the fingers will still meet at the balancing point, the center of mass.
Professor Peter Schlein suggests this further demonstration of torque: Hold one end of the meter stick between your thumb and finger as shown above, and slide your index finger in from the other end. The force on your sliding finger increases from half the weight of the meter stick when your finger is at the far end to the full weight when your finger is at the center and the whole weight of the meter stick balances on one finger. As you slide your finger beyond the center towards the held end, your thumb must now exert a downward force, and the force on your sliding finger becomes extremely large. You can calculate the torques by assuming that the weight of the sections of the meter stick act at the centers of the sections.
Links:
[1] https://demoweb.physics.ucla.edu/node/412
[2] https://demoweb.physics.ucla.edu/node/429