The diagram above shows a plank RS pivoted its center of gravity O and is in equilibrium with the weight P and Q. If a weight 2P is added to P the plank wil...

Answer Details

The plank is in equilibrium because the weight of P and Q are balanced by the weight of the plank itself, which is acting downwards through its center of gravity O. When a weight 2P is added to P, the equilibrium of the plank will be disturbed, and it will tilt downwards on the side where the weight has been added. To restore equilibrium, the weight of 2P must be balanced by an equal and opposite weight on the other side of the pivot. This can be achieved by moving Q nearer to O. By doing so, the weight of Q acting downwards through the center of gravity O will increase, and the plank will tilt back up, restoring equilibrium. The other options listed are not correct. Moving P nearer to O or adding a weight Q to Q would not restore equilibrium, as they would not provide the necessary counterbalancing weight to balance 2P. Moving P further away from O would also not work, as it would increase the weight acting downwards on that side of the pivot, making the plank tilt even further in that direction.