Torsional Pendulum

Oscillation of mass on wire in torsional mode of oscillation.

torsion pendulum

What It Shows

The frequency of oscillation of a torsional pendulum is proportional to the square root of the torsional constant and inversely proportional to the square root of the rotational inertia.

How It Works

A heavy gauge steel wire is held vertically under tension within a welded frame. The frame is able to be clamped to the lecture bench. Clamped to the wire is a thin aluminum platform that is able to oscillate in the horizontal plane. Two pairs of holes, each capable of holding a 1-inch ball bearing, have been cut out of the plate at 6cm and 29cm from the central torsion wire. A noticeable change to the oscillation frequency can be observed as the ball bearings are moved from the outer holes to the inner ones.

Setting It Up

The edges of the aluminum plate are sharp, so make sure to stand clear and watch your fingers as the platform swings!