Equilibrium

1. Prepared By
Muhammad Abid
S7285
06-07-2015

2. A body is said to be in
equilibrium if it is at rest or
moving with uniform velocity.
In other words if the linear and
angular acceleration of a body are
zero, the body is said to be in
equilibrium.
Or we can say that when two or more forces act on
a body such that their resultant or combining
effect on the body is Zero and the body retains its
state of rest or of uniform motion then the body is
said to be in equilibrium.

3. With respect to the state of a body,
equilibrium may be divided into two
categories:

1. Static equilibrium.
2. Dynamic equilibrium.

4. If the combined effect of all
the forces acting on a body is
zero and the body is in the
state of rest then its
equilibrium is termed as
static equilibrium.
For example: All
stationary bodies
Static equilibrium

5. when a body is in state
of uniform motion and
the resultant of all the
forces acting upon it is
zero then it is said to be
in dynamic
equilibrium.
For example: Jump by
using parachute.
Dynamic equilibrium

6. There are three states of equilibrium:
Stable equilibrium
Unstable equilibrium
Neutral equilibrium

7. A body is said to be in stable equilibrium if it comes
back to its original position when it is slightly
displaced.
When a body which is in stable equilibrium is
disturbed its centre of gravity is raised.
For example a book lying on a table is in stable
equilibrium.

8. A body is said to be in unstable
equilibrium if it does not come back to its
original position when it is slightly
displaced
When a body which is in unstable
equilibrium is disturbed its centre of
gravity is lowered
Example: pencil standing on its point or a
stick in vertically standing position

9. If a body is placed in such state that if it is
displaced then neither it topples over nor does
it come back to its original position, then such
state is called neutral equilibrium.
When a body which is in neutral equilibrium is
disturbed its centre of gravity is neither raised
nor lowered but it remains at the same height.
Example: rolling ball