When does a body rotate? State one way to change the direction of rotation of the body. Give a suitable example

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A body rotates when a net torque acts on it. To reverse the rotation about a fixed axis, apply a retarding (opposite) torque until it stops, then it will start rotating the other way.
If the axis is not fixed, you can reverse the rotation simply by reversing the axis of rotation (changing the orientation of the axis).
Since torque causes rotation, you can change the rotation direction by applying an opposite torque or reversing the torque direction. By Newton’s first law, motion changes only when an external force/torque acts.
Right-hand rule: curl the fingers of your right hand in the direction of rotation; your thumb points along the directions of angular velocity and angular momentum.
Example: A force applied at a suitable point on a pivoted body produces a torque about the pivot, causing rotation. Changing the point or direction of the applied force can reverse the rotation.

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