State and explain the principle of moments.  Draw a diagram to illustrate.

Asked by Topperlearning User | 4th Jun, 2014, 01:23: PM

Expert Answer:

Principle of Moments: According to this principle, in equilibrium the sum of the anticlockwise moments is equal to the sum of the clockwise moments.

To illustrate the principle, let us consider a uniform rod of length (d1+d2) resting on a knife edge. Let two forces F1& F2 (such as F1> F2) are applied on its two ends (both in same downward direction). Since the two forces are unequal, the equilibrium point is not in the middle but towards the larger force F1.

Force  F2 tends to turn the rod clockwise, while the force F1 tends to turn the rod anticlockwise.
i.e. Clockwise moment = F2 x d2
     Anticlockwise moment  = F1 x d1 

In equilibrium,  Clockwise moment = Anticlockwise moment
                 i.e.      = F2 x d2 = F1 x d1 
This illustrates the principle of moments.

Answered by  | 4th Jun, 2014, 03:23: PM