Work, Energy, Power and Machines

Syllabus tag: KCSE | Physics | Form 3 | Topic 24 Work, Energy, Power and Machines

Lesson objectives

By the end of this topic, you should be able to:

• Define work, energy and power and state their units.
• State the law of conservation of energy and apply it.
• Define mechanical advantage, velocity ratio and efficiency.
• Describe the common machines and solve problems on them.

Summary

Work is force × distance moved in the direction of the force, measured in joules. Power is the rate of doing work, in watts. Energy is never created or destroyed, only converted. For any machine, MA = load ÷ effort, VR = effort distance ÷ load distance, and efficiency = (MA ÷ VR) × 100 %.