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.