1. Positive Work: Positive work is done when the force applied to an object is in the same direction as the object's displacement. In this case, the work done increases the kinetic energy of the object. For example, when you lift a book from the ground to a shelf, you do positive work on the book. The force you apply (upward force) is in the same direction as the displacement of the book (upward displacement). As a result, the book gains kinetic energy and moves upward.
2. Negative Work: Negative work is done when the force applied to an object is opposite in direction to the object's displacement. In this case, the work done decreases the kinetic energy of the object. For example, when you apply friction to a moving object, such as a car, the force of friction opposes the motion of the car (forward displacement). As a result, the car loses kinetic energy and slows down.
The amount of mechanical work done is calculated using the following formula:
Work (W) = Force (F) × Displacement (d) × cosθ
Where:
F = Magnitude of the force
d = Magnitude of the displacement
θ = Angle between the force and displacement vectors
The unit of measurement for work is Joules (J), which represents the amount of work done when a force of one Newton (N) is applied to move an object one meter (m) in the direction of the force.
It's important to note that mechanical work involves the transfer of energy from one form to another. In the case of positive work, energy is transferred from the person or system doing the work to the object being moved. In the case of negative work, energy is transferred from the object being moved to the person or system doing the work.
