# By using an oscillating pendulum, if we take time for the pendulum to swing from A to C to B again, it takes 3 seconds.What is the period of the pendulum?

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The nature of movement described in the question is not very clear. Because of this it is not possible to determine the period of the pendulum.

To ascertain the period of a pendulum we have to measure the time it takes for the pendulum to to complete one oscillation. That is to return to a given position after having swung to its extreme positions. Thus if P and R are two extreme position of the bob of a pendulum and Q is a position between these two extreme. starting from the point Q one complete oscillation of the pendulum will consist of:

- the bob initially moving to any one of the two extreme points, say P, then
- reversing its direction to move towards the point R,
- crossing point Q on its way to point R,
- reaching point R,
- reversing its direction to move towards P, and finally
- crossing the original point Q on its way to P.

To make it easier to measure the time of oscillation, it is better to start from one of the extreme point, say P. In this case one oscillation will consist of the bob moving from P to R and again returning to P.

Also, the accuracy of observation can be improved by timing several continuous oscillation and then dividing the total time taken for these by the number of oscillation to get the time per oscillation.