Observing slow oscillations

A mass–spring system

A trolley, loaded with extra masses, is tethered by identical springs in between two clamps (Figure 18.3). Move the trolley to one side and it will oscillate back and forth along the bench. Listen to the sound of the trolley moving. Where is it moving fastest? What happens to its speed as it reaches the ends of its oscillation? What is happening to the springs as the trolley oscillates?

A long pendulum

A string, at least $2 m$ long, hangs from the ceiling with a large mass fixed at the end (Figure 18.4). Pull the mass some distance to one side, and let go. The pendulum will swing back and forth at its natural frequency of oscillation. Try to note the characteristics of its motion. In what ways is it similar to the motion of the oscillating trolley? In what ways is it different?

A loudspeaker cone

A signal generator, set to a low frequency (say, 1 Hz), drives a loudspeaker so that it vibrates (Figure 18.5). You need to be able to see the cone of the loudspeaker.
How does this motion compare with that of the pendulum and the mass–spring system? Try using a higher frequency (say, $100 Hz$). Use an electronic stroboscope flashing at a similar frequency to show up the movement of the cone. (It may help to paint a white spot on the centre of the cone.) Do you observe the same pattern of movement?