The laws of a simple pendulum - QS Study
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1st law or the law of isochronism:

The time period (T) is constant, when effective length (L) and gravity (g) are constants. This means that a pendulum will take same time in completing each oscillation, whatever is the amplitude, provided the latter does not exceed 4o. So the time period of oscillation of a simple pendulum is independent of amplitude of vibration, provided its amplitude does not exceed 4o.

2nd law or the law of length:

When acceleration due to gravity (g) is constant, the time period (T) of oscillation of a simple pendulum is directly proportional to the square root of its effective length (L).

So, T ∞ √L, when g is constant.

3rd law or the law of acceleration:

When effective length (L) is constant, the time period (T) of oscillation of a simple pendulum is inversely proportional to the square root of the acceleration due to gravity (g) at a place of observation.

So, T ∞ √1/g, when L is constant.

4th law or the law of mass:

The time period of oscillation of a pendulum at a place independent of mass and material of the bob provided the effective length of the pendulum is constant.