One swing, one time period

The idea

One oscillation is the bob's movement from the mean position to one extreme, to the other extreme and back (or from one extreme to the other and back); the time taken for one oscillation is the time period.

Counting swings

The bob starts at the middle, O. It goes to A on one side, then to B on the other side, and comes back to O.

How many oscillations is that?

• One
• Two
• Four

Time one oscillation

Start at O or at A. Watch the path and the stopwatch.

The time period

Going from O to A to B and back to O is one oscillation. So is going from A to B and back to A. The time it took is the time period.

One oscillation is the bob's movement from the mean position to one extreme, to the other extreme and back (or from one extreme to the other and back). The time taken for one oscillation is the time period.

Notes

One oscillation is the bob's movement from the mean position to one extreme, to the other extreme and back (or from one extreme to the other and back). The time taken for one oscillation is the time period.

Check yourself

The pendulum bob moves from O to A, then to B, and back to O. How many oscillations is that?

The time taken for one oscillation is called the …

The bob goes from A to B and back to A. This is …

A pendulum has a time period of 2 s (an example). How many seconds does it take to complete 1 oscillation?

Answer: 2 s

The time period is the time taken for one oscillation: 2 s.

• Two. The bob made just one full trip: O to A to B and back to O.
• One — correct. Yes!
• Half. That path is a complete oscillation, not half of one.
• mean position. The mean position is where the bob hangs at rest.
• extreme position. An extreme position is one end of the swing.
• time period — correct. Yes!
• one oscillation — correct. Yes!
• half an oscillation. From A to B and back to A is a complete oscillation.
• two oscillations. It is one oscillation, since the bob has come back to where it started.