Equilibrium of Body Class 10 Physics ICSE

Equilibrium of Bodies

When a number of forces acting on a body produce no change in its state of rest of linear motion or rotational motion, the body is said to be in a state of equilibrium.

1. Static equilibrium

A number of forces acting on a body and the body remains in the state of rest under the influence of those forces.

ex:1 when two equal and opposite forces act up on a body lying on a flat surface, the body remains at rest. Hence that body is in static equilibrium.

ex: 2 The beam balance with equal weights on both pans is in static equilibrium because the anticlockwise moment of force balances the clockwise moment of force.

2. Dynamic Equilibrium

If a body remains in the state of motion (translational or rotational) under the influence of several forces then that body is said to be dynamic equilibrium.

ex 1 : The weight of a falling rain drop balances the sum of the buoyant force and the force due to friction. Hence the falling rain drop  will be in dynamic equilibrium and falls down with a constant velocity.

ex 2 : When the weight of an aeroplane is balanced by the upward lift  the aeroplane moves at a constant height.

Conditions for equilibrium:

1. The resultant of all the forces acting the body should be zero.

2. The algebraic sum of moments of all the forces acting on the body about the point of rotation should be zero.