CHAPTER 4: WORK, ENERGY, POWER & MACHINES

Work, Energy, and Power are interconnected concepts that describe how forces cause changes in the world. Machines are devices that make work easier by multiplying force or changing its direction. This chapter gives you the tools to understand everything from a simple lever to the power output of an engine.

4.1 WORK

In physics, "work" has a very specific meaning. It is not just any effort; it is the product of force and the distance moved in the direction of the force.

4.1.1 Definition of Work

Work is done when a force moves an object in the direction of the force.

Work (W) = Force (F) × Distance moved in the direction of the force (d)

Where:

• W = work done (in Joules, J)
• F = force applied (in Newtons, N)
• d = displacement in the direction of the force (in metres, m)

4.1.2 Conditions for Work to be Done

• A force must be applied.
• The object must move.
• The movement must be in the direction of the force (or have a component in that direction).

If you push against a wall and it doesn't move, you have done NO work in the physics sense. You may be tired, but no energy has been transferred mechanically to the wall.

4.1.3 The Joule (Unit of Work and Energy)

From the formula: 1 Joule = 1 Newton × 1 metre.

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