Simple Harmonic Motion and Explanation

Q. What do you understand by simple Harmonic Motion? and  Explain Simple Harmonic Motion with the help of a Simple Pendulum.

Simple Harmonic Motion
A body is said to have simple Harmonic Motion if its acceleration is always direct ed towards a fixed point and its magnitude is proportional to the displacement of the body from its mean position.

Explanation of Simple Harmonic Motion with the Help of Simple Pendulum
The common example of Simple Harmonic Motion is swinging back and forth of a Simple Pendulum. An ideal Pendulum consists of a point mass suspended by a weightless and in extensible string from a fixed support.
If we displace the bob from its mean position o to a new position A and allow it to go, it will move towards 0 under the action of gravity. The bob will not come to rest at 0, but due to inertia it will continue to move towards a point B. While moving from 0 to B, the bob is moving against gravity. Its velocity goes on decreasing and ultimately becomes zero at the point B. From here the bob will come back from B to 0 under the action of Gravity. Its velocity continues to increase till it becomes maximum on reaching the mean position 0. The bob will not stop at 0 but continues to move towards A due to inertia. As the bob is moving against gravity from 0 to A, its velocity decreases and becomes zero at A. In this way tile whole process is repeated again and again and the bob continues to vibrate, moreover it is observed that in this case the acceleration is always directed towards mean position and its magnitude is directly proportional to the displacement of the body .from its mean position. Hence we conclude that the motion of the Pendulum is Simple Harmonic.


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