PhysicsA LevelThermal & Gases

Kinetic theory formula

The kinetic theory formula as it is used in A Level Physics, taken from the A Level Physics formula sheet.

The formula

12mc2=32kT\tfrac{1}{2}m\overline{c^2} = \tfrac{3}{2}kT

How to use it in the exam

  • Write the formula down before substituting — most mark schemes award a method mark for a correct, clearly quoted formula.
  • Check every quantity is in consistent units before you substitute, then substitute in one step so the working stays easy to follow.
  • Show the rearrangement rather than jumping to the answer, and give the final value to the accuracy the question asks for.

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