What It Is

Science calculations appear on every OCR Combined Science paper. You need to memorise key equations, know how to rearrange them, and practise substituting values correctly. Many students lose marks not because they don’t understand the science, but because they make errors in the maths.

Key Equations to Memorise

These equations are commonly required and may not be given on the paper:

• Speed: \(v = \frac{s}{t}\)
• Acceleration: \(a = \frac{\Delta v}{t}\)
• Force: \(F = ma\)
• Work done: \(W = Fs\)
• Kinetic energy: \(KE = \frac{1}{2}mv^2\)
• GPE: \(GPE = mgh\)
• Power: \(P = \frac{E}{t}\) and \(P = IV\)
• Ohm’s law: \(V = IR\)
• Density: \(\rho = \frac{m}{V}\)
• Pressure: \(P = \frac{F}{A}\)

How to Practise

1. 1
   Write them all from memory — Cover the list and write every equation you can recall. Check and note the gaps.
2. 2
   Practise rearranging — For each equation, make each variable the subject. If \(F = ma\), also practise \(m = \frac{F}{a}\) and \(a = \frac{F}{m}\).
3. 3
   Practise with numbers — Use StudyVault practice questions or past paper calculation questions. Show full working every time.
4. 4
   Check units — Always convert to standard units before substituting (kg not g, m not cm, s not minutes).