Torque or Turning effect of Force


  

Do you know why hinge of door is only given to position a or not b??? 

This is because torque is maximum when it's distance from perpendicular axis is more so it can be turned easily for small amount of force 

                     Torque Definition

Moment of force, mathematically, is the product of this force and perpendicular distance between the line of action of the forces

                      Another example 

                      Turning a tap 
                    Opening bottle cap
                    Gearing a bicyle