Non-uniform Physical Pendulum
simple harmonic motion - period of oscillation - moment of inertia
What it shows:
The period of a physical pendulum is measured and compared to theory:
where I is the rotational inertia, g is the acceleration due to gravity, and x is the distance from
the pivot to the center-of-mass. For a uniform rod, the center-of-mass is literally at the center
of the rod. In this demonstration the physical pendulum is half steel and half wood so that the
center-of-mass location is non-trivial, but can be found by balancing the pendulum. The moment
of inertia about each pivot can then be determined from
How it works:
The physical pendulum is a 2 cm square by 92 cm long "rod," half of which is steel and the other
half wood. Small holes positioned 1.5 cm from each end serve as suspension pivot points.
A digital wristwatch or large analog timer
1
is used to measure the period when the pendulum is swung from each of the two pivots.
Setting it up:
Use standard lab clamps and rods mounted on the lecture bench. Rating *
1 Sargent-Welch Scientific model 812