Condition of equilibrium when body is acted upon by a number of parallel forces

Explanation:

For an object to be in equilibrium, it must be experiencing no acceleration. This means that both the net force and the net torque on the object must be zero. Here we will discuss the first condition, that of zero net force.

In the form of an equation, this first condition is:

F

net

=

0

.

In order to achieve this conditon, the forces acting along each axis of motion must sum to zero. For example, the net external forces along the typical x– and y-axes are zero. This is written as

net  

F

x

=

0

and  

net  

F

y

=

0

.

The condition  

F

net

=

0

must be true for both static equilibrium, where the object’s velocity is zero, and dynamic equilibrium, where the object is moving at a constant velocity.

Below, the motionless person is in static equilibrium. The forces acting on him add up to zero. Both forces are vertical in this case.

the force on the thing and the distance the force moves the thing