Work

Definition: Work is the measure of energy transfer when a force acts on an object and causes it to move in the direction of the force. Mathematically, it is represented as the dot product of force (F) and displacement (d):

W=Force ⋅ displacement

W=F.d

Keep this in mind that work is only done if there is a change in position. If you stay at the same place and read 50 books for an exam, its still not work according to physics.

Key Points:

• No Work: When the force is perpendicular to the displacement, or if there’s no displacement, no work is done (W = 0) because the force does not contribute to moving the object in the direction of the displacement.

Imagine pushing a box across a floor. If you push the box horizontally, it moves in that direction, and you’re doing work. However, if you push the box downward while it’s moving horizontally, you’re just pressing it against the floor without making it move any faster or further in the direction it’s already going. In this case, your downward push (force) doesn’t help with the horizontal movement (displacement). Thus, no work is done by the perpendicular force.

• Units: The unit of work is the joule (J), and it is a scalar quantity (it only has magnitude and no direction). One joule is equal to one newton-metre (1 J = 1 N⋅m). It means one Newton of force was used to move the object through a displacement of 1 metre.

Analogy: Consider pushing a shopping cart:

• Positive Work: Pushing it in the direction you want to go.

• Negative Work: Pushing it backward.

• No Work: Holding it still without moving.