A body acted upon by two or more forces is said to
be in equilibrium if it does not move or rotate under this condition, the sum
of the forces moving the body in one direction is equal to the sum of the
forces pushing the body in the opposite direction.
be in equilibrium if it does not move or rotate under this condition, the sum
of the forces moving the body in one direction is equal to the sum of the
forces pushing the body in the opposite direction.
Resultant and equilibrium forces
In the
force board experiment, the resultant R of two forces P and Q acting at a point
O was found by the parallelogram method to be equal in magnitude but exactly
opposite M direction to the third force that kept the point Q in
equilibrium. This third force which is
equal but opposite in direction to the resultant force is known as the
equilibrant force. This equilibrant
force counter balances the other two forces P and Q.
force board experiment, the resultant R of two forces P and Q acting at a point
O was found by the parallelogram method to be equal in magnitude but exactly
opposite M direction to the third force that kept the point Q in
equilibrium. This third force which is
equal but opposite in direction to the resultant force is known as the
equilibrant force. This equilibrant
force counter balances the other two forces P and Q.
Note: The resultant force is that
single force which acting alone will have the same effect in magnitude and
direction as two or more forces acting together.
single force which acting alone will have the same effect in magnitude and
direction as two or more forces acting together.
The
resultant force is found by the parallelogram law of vectors.
resultant force is found by the parallelogram law of vectors.
Note: The equilibrant of two or more
forces is that single force which will balance all the other forces taken
together. It is equal in magnitude but
opposite in direction to the resultant force.
forces is that single force which will balance all the other forces taken
together. It is equal in magnitude but
opposite in direction to the resultant force.
If three forces F1,
F2 and F3 acting at a point are in equilibrium, the
resultant of any two of the forces is equal but opposite in direction to the
third force. Any of these forces is said
to be the equilibrant of the other two.
The equilibrant of f1 and f2 is f3, the
equilibrant of f2 and f3 is f1 and the equilibrant
of f1 and f3 is f2.
F2 and F3 acting at a point are in equilibrium, the
resultant of any two of the forces is equal but opposite in direction to the
third force. Any of these forces is said
to be the equilibrant of the other two.
The equilibrant of f1 and f2 is f3, the
equilibrant of f2 and f3 is f1 and the equilibrant
of f1 and f3 is f2.
Three
forces in equilibrium
forces in equilibrium
Also, the line of action of the three forces
keeping a body in equilibrium must all pass through one point. Otherwise, the resultant of two of the forces
cannot be counter balanced by the third force.
keeping a body in equilibrium must all pass through one point. Otherwise, the resultant of two of the forces
cannot be counter balanced by the third force.
Example:
Two forces 10N each are inclined at 1200
to each other. Find the angle force that
will;
to each other. Find the angle force that
will;
a) Replace
the given force system.
the given force system.
b) Balance
the given force system
the given force system
Note: Hence Equilibrant
= 10N directed opposite to the resultant B.
= 10N directed opposite to the resultant B.
