A flat bar free to rotate about its center is accelerated by the torque provided by a string-wrapped disc and hanging weight. Two weights attached to the bar may be removed, placed close to the center of the bar or at the ends of the bar for three different moments of inertia.
The aformentioned weights are 1045 g each. The bar is 91.4 cm long and weighs 445 g. The inner and outer attachment points are located 7.0 cm and 41.9 cm, respectively, from the axis of rotation. Accelerating weights may be varied, and can be hung on either a 10 cm or 20 cm diameter disc to change torque - observe varying angular accelerations. More information is printed on an accompanying info card.