OCR GCSE Physics Notes | P7
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- Law of conservation of energy: energy cannot be created or destroyed, only transferred (usefully or wastefully).
- Work done: energy transferred.
- Chemical energy: stored in batteries/ muscles.
- Gravitational potential energy: energy transferred in a falling object.
- Kinetic energy: energy transferred in a moving object.
- Elastic potential energy: energy transferred in a stretched object.
- Energy transfers in a kettle: electrical, thermal, sound, kinetic.
- Energy transfers in a calculator: chemical, light.
- Energy transfers in a tennis ball dropped: gravitational potential to kinetic.
- Heating an object: particles gain more kinetic energy, to overcome its specific heat capacity.
- Work done = force x distance.
- Ek = 0.5mv2
- Ep = mgh
- Ee = 0.5ke2
- E: energy (J), m: mass (kg), v: speed (m/s), g: 9.8m/s2, h: height (m), k: spring constant, e: extension (m), P: power (W).
- E = Pt
- Energy can be measured in kilowatt-hours to make things easier.
- Power is the rate of energy transferred.
- Efficiency = (useful energy/ total energy used) x 100%
- Energy can be wasted as heat, sound or light depending on the system.