Energy, work & power

Notes

What you need to know

• Identify and describe different energy stores: gravitational PE, kinetic, chemical, thermal, elastic, nuclear, electromagnetic
• State the principle of conservation of energy: energy cannot be created or destroyed
• Describe energy transfer chains for common situations (falling object, burning fuel, pendulum)
• Draw and interpret Sankey diagrams with arrow widths proportional to energy amounts
• Recall and use W = Fd to calculate work done, force, or distance
• State that work done equals energy transferred and understand the conditions for work to be done
• Find work done from the area under a force–distance graph
• Recall and use P = W/t = E/t to calculate power, energy, or time
• Use P = Fv for an object moving at constant velocity under a constant force (Extended)
• Recall and use ΔE_p = mgΔh for gravitational potential energy
• Recall and use E_k = ½mv² for kinetic energy
• Apply conservation of energy to convert between GPE and KE (with and without energy losses)
• Calculate efficiency as useful energy output ÷ total energy input; use as a fraction or percentage
• Use efficiency = useful power output ÷ total power input (Extended)

Syllabus subtopics

• Energy stores
• Energy transfers and conservation
• Kinetic and gravitational potential energy
• Work done
• Energy resources
• Power
• Efficiency