✏️ Paper first! Work out every question on paper before you open the answer. Write down every step – the equation, the numbers with units, the rearranging and the answer with its unit. In the exam, if your final answer is wrong you can still get marks for correct working, but only if the examiner can see it.
Calculate momentum, use conservation of momentum for collisions and explosions, and link force to the rate of change of momentum. Before and after diagrams for every question.