Work, Energy & Power

What this lesson covers

Work, Energy & Power is a 8-part Class 9 Physics lesson. Each part makes one point and then hands over to the next, so it can be read in a sitting or picked up again at the part you stopped on. It defines the idea in plain words before using it, works through an example step by step, breaks the topic into its parts and compares them, shows where it is used outside the textbook, names the mistakes that cost marks in an exam, ends with a recap of what to remember.

How it begins

In physics, work is done only when a force moves something in the direction of the force. W = F × d (joules)Hold a heavy bag still for an hour and you will feel exhausted, but in physics terms you have done zero work: nothing moved. Carry it horizontally and you still do no work against gravity, because the force is vertical and the motion is horizontal.

The 8 parts

1. Work, in the physics sense
2. Forms of energy
3. The four equations
4. Following the energy
5. Energy in the real world
6. Where marks get lost
7. What to remember
8. Watch one worked through