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Theory:

In the previous section, we looked into the definition of work. In this section, we are going to see
  • Whether force is unidirectional or not.
  • Whether work done by a force is positive or negative.
Consider the case in which the force and the displacement are in the same direction:
  • A girl pulls a toy car that is parallel to the ground, as shown in figure.
2.png
  • The baby applies a force in the direction of displacement of the vehicle.
shutterstock_144732055.jpg

In these cases, the work done will be equal to the product of the force and displacement.
 
Workdone=Force×Displacement
 
In such cases, the work done by the force is taken as positive.
 
Consider the scenario in which an object moves with a uniform velocity along a particular direction.
 
Retarding force, \(F\), is applied in the opposite direction to the object's movement. That is, the angle between the two directions is \(180º\). Let the object stops after a displacement \(s\).
 
In such cases, the work done by the force, \(F\), is taken as negative and denoted by the minus sign.
 
Workdone=Force×DisplacementWorkdone=F×sorWorkdone=F×s
 
From the above discussion, the work done by a force can be either positive or negative.