Study Notes
Energy, work, and power are fundamental concepts in physics that describe how energy is stored, transferred, and conserved in various forms. Energy can be stored as kinetic, gravitational potential, chemical, elastic, nuclear, and internal energy, and it is transferred during events and processes without being created or destroyed, following the principle of conservation of energy.
- Energy — the capacity of something to do work. Example: A book on the table possesses 20J of potential energy.
- Kinetic Energy — energy an object has due to its motion. Example: A moving car has kinetic energy.
- Gravitational Potential Energy — energy an object has due to its height. Example: An apple hanging on a tree has gravitational potential energy.
- Power — the rate at which work is done or energy is transferred. Example: A light bulb uses power to emit light.
- Efficiency — the ratio of useful energy output to total energy input, often expressed as a percentage. Example: An LED bulb is more efficient than an incandescent bulb.
Exam Tips
Key Definitions to Remember
- Energy is the capacity to do work.
- Kinetic energy is energy due to motion.
- Gravitational potential energy is energy due to height.
- Power is the rate of doing work.
- Efficiency is the ratio of useful output to total input energy.
Common Confusions
- Confusing energy transfer with energy creation.
- Misunderstanding that only speed is squared in the kinetic energy formula.
Typical Exam Questions
- What happens to energy when an apple falls from a tree? It converts from gravitational potential energy to kinetic energy.
- How do you calculate the work done by a force? Work done = force x distance moved in the direction of the force.
- What is the efficiency of a device that outputs 50J of useful energy from 100J of input energy? Efficiency = 50%.
What Examiners Usually Test
- Understanding of energy conservation.
- Ability to calculate kinetic and potential energy.
- Application of efficiency formulas.