Download The first condition of equilibrium is that the net force in all

The first condition of equilibrium is that the net force in all directions
must be zero.
LEARNING OBJECTIVE [ edit ]
Identify the first condition of equilibrium
KEY POINTS [ edit ]
There are two conditions that must be met for equilibrium.
The same conditions apply both to static equilibrium anddynamic equilibrium.
If net force is zero, then net force along any direction is zero.
TERMS [ edit ]
translation
Motion of a body on a linear path, without deformation or rotation, i.e. such that every part of the
body moves at the same speed and in the same direction; also (in physics), the linear motion of a
body considered independently of its rotation.
torque
A rotational or twisting effect of a force; (SI unit newton-meter or Nm; imperial unit foot-pound
or ft-lb)
force
A physical quantity that denotes ability to push, pull, twist or accelerate a body which is measured
in a unit dimensioned in mass × distance/time² (ML/T²): SI: newton (N); CGS: dyne (dyn)
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First Condition of Equilibrium
An object that is motionless or undergoes
no translational and
rotational acceleration is said to be in
equilibrium. That is, the net force and
net torque on the object is zero in all
directions. For an object to truly be in
equilibrium, two conditions must be met.
The first condition states that the net force
acting on the object must be zero. This
means that for each axis of motion, the
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forces acting along that particular axis
must sum to zero.
Expressed as an equation, this is simply:
netF = 0
.
Note that if net F is zero, then the net external force in anydirection is zero. For example, the
net external forces along the typical x- and y-axes are zero. This is written as
netF x = 0
and netF
y
= 0
.
and illustrate situations where netF
= 0
for both static equilibrium (motionless), and
dynamic equilibrium (constantvelocity). In , the motionless person is in static equilibrium.
The forces acting on him add up to zero. Both forces are vertical in this case. In , the car is in
dynamic equilibrium because it is moving at constant velocity. There are horizontal and
vertical forces, but the net external force in any direction is zero. The applied force F app
between the tires and the road is balanced by air friction, and the weight of the car is
supported by the normalforces, here shown to be equal for all four tires.
Dynamic Equilibrium
This car is in dynamic equilibrium because it is moving at constant velocity. There are horizontal
and vertical forces, but the net external force in any direction is zero. The applied force Fapp
between the tires and the road is balanced by air friction, and the weight of the car is supported by
the normal forces, here shown to be equal for all four tires.
Static Equilibrium
This motionless person is in static equilibrium. The forces acting on him add up to zero. Both forces
are vertical in this case.
But remember, for true equilibrium, condition 1 is only half the picture.
Static Equilibrium
This motionless person is in static equilibrium. The forces acting on him add up to zero. Both forces
are vertical in this case.