AQA GCSE Physics: Energy Notes

Energy Calculations and Types

You'll encounter three main types of energy calculations in your exams, and they're easier than they look! Kinetic energy measures the energy of moving objects using the formula Ek = ½mv², where m is mass in kg and v is speed in m/s.

Gravitational potential energy (GPE) calculates stored energy when objects are lifted up. The formula GPE = mgh uses mass (kg), gravitational field strength (9.8 N/kg on Earth), and height $m$. Think of it as the energy stored in a book on a shelf.

Elastic potential energy appears when you stretch springs or elastic bands. Using Ee = ½ke², where k is the spring constant and e is extension, you can work out how much energy is stored. The stiffer the spring, the more energy it stores.

Quick Tip: Remember that all energy is measured in Joules (J), and these three formulas are your best friends for energy calculations!

Internal Energy and Specific Heat Capacity

Internal energy might sound complex, but it's simply the total kinetic and potential energy of all particles in a system. When you heat something up or do work on it, you're increasing its internal energy.

Specific heat capacity tells you how much energy (in Joules) you need to heat 1kg of a substance by 1°C. Water has a high specific heat capacity $4200 J/kg°C$, which is why it takes ages to boil a kettle! Different materials heat up at different rates.

The key formula is ΔE = mcΔθ, where ΔE is the change in thermal energy, m is mass, c is specific heat capacity, and Δθ is temperature change. This formula helps you calculate exactly how much energy you need to heat something up.

Exam Success: Practice rearranging these formulas using the triangle method - it's a guaranteed mark-saver when you need to find mass or temperature change instead of energy!