A physical pendulum with a magnetic load is proposed for comparison of linear and nonlinear oscillations. The magnetic load is repelled by permanent magnets which are disposed symmetrically relative to the load. It is established that positions of the pendulum and the magnets determine the dependence of restoring force on displacement of the load. The dependence can be both linear and nonlinear. The apparatus is equipped with a photoelectric transducer. The signal goes to a computer and is displayed on the monitor as the dependence of the oscillation period on its number. If the position of the pendulum is normal then the oscillations are approximately linear. If the pendulum is turned over then its oscillations become substantially nonlinear.