Summary
The topic of work, energy, and power involves understanding how forces cause movement, how energy is transferred and conserved, and how power is the rate of doing work. Energy can be stored in various forms and transferred through different processes, while power measures how quickly work is done or energy is transferred.
- Work — the product of force and distance when a force causes displacement. Example: Pushing a box across the floor involves work done by the force applied over the distance moved.
- Kinetic Energy (K.E.) — energy an object has due to its motion. Example: A moving car has kinetic energy.
- Gravitational Potential Energy (G.P.E.) — energy an object has due to its position in a gravitational field. Example: A book on a shelf has gravitational potential energy.
- Conservation of Energy — principle stating energy cannot be created or destroyed, only transformed. Example: A pendulum converts kinetic energy to potential energy and back, with total energy constant.
- Power — the rate at which work is done or energy is transferred. Example: A light bulb uses power to convert electrical energy into light and heat.
Exam Tips
Key Definitions to Remember
- Work: Force applied over a distance
- Kinetic Energy: Energy due to motion
- Gravitational Potential Energy: Energy due to position in a gravitational field
- Power: Rate of doing work or transferring energy
Common Confusions
- Confusing energy conservation with energy loss
- Misunderstanding that no work is done if there is no movement
Typical Exam Questions
- What is work done when a force of 10 N moves an object 5 m? Work done is 50 J (joules)
- How does energy change when a ball is thrown upwards? Kinetic energy converts to gravitational potential energy
- What is the power of a machine that does 100 J of work in 5 seconds? Power is 20 W (watts)
What Examiners Usually Test
- Understanding of energy transformations and conservation
- Ability to calculate work, energy, and power
- Application of concepts to real-world scenarios