Class 11 Physics Rotational Motion Equilibrium of Rigid Body

Equilibrium of Rigid Body

• A force changes the translational state of the motion of the rigid body, i.e. it changes its total linear momentum.
• A torque changes the rotational state of motion of the rigid body, i.e. it changes the total angular momentum of the body

Note: Unless stated otherwise, we shall deal with only external forces and torques.

• A rigid body is said to be in mechanical equilibrium, if both its linear momentum and angular momentum are not changing with time. This means
• Total force should be zero => Translational Equilibrium
• Total torque should be zero => Rotational Equilibrium

• A pair of equal and opposite forces with different lines of action is known as a couple or torque. A couple produces rotation without translation.

• When you open the lid of a jar , you apply couple on it

• An ideal lever is essentially a light rod pivoted at a point along its length. This point is called the fulcrum
• The lever is a system in mechanical equilibrium.

• Mechanical advantage greater than one means that a small effort can be used to lift a large load.

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