RESULTANT OF TWO FORCES

Definition 

The net effect of the forces is a single force which is called the resultant of the forces. 
                                                                    OR 
A single that gives combined effect of forces is called resultant force. 

 

If two forces F1 and F2 are acting on a body at a straight line but in opposite direction and body remains at rest or in equilibrium. Then we say that F1 and F2 are equal in magnitude but opposite in direction. 

If two forces F1 and F2 are acting on a body at a straight line but in opposite direction and body moves in the direction of any one of them which is greater than the other. Net force is calculated as: 

                               F2-F1 net force
                   or        F1-F2 net force
            Body will move in the direction of greater force.

RESULTANT OF TWO FORCES ACTING AT AN ANGLE

 If two forces are acting on an object making a certain angle. In this case the force can be represented in magnitude and direction by two adjacent sides of a parallelogram (I In). The resultant force FR is a vector represented by the diagonal from the point of intersection. This is called the parallelogram of forces.

As PR is diagonal of I Im PQRs so the resultant is diagonal. And the I Im is called I Im of force F1 and F2. 


By head to tail rule, we can draw force F- from the terminal point of force F2. To get the resultant FR we draw a vector from the initial point of force F2 to the terminal point of the force Fr. This is the same force as obtained from the I l 1 of force as shown in the figure.