This higher tier covers Higher Tier: Inertial Mass within Newton's Laws of Motion for GCSE Physics. Revise Newton's Laws of Motion in Forces for GCSE Physics with 24 exam-style questions and 15 flashcards. This topic shows up very often in GCSE exams, so students should be able to explain it clearly, not just recognise the term. It is section 12 of 15 in this topic. This section is most useful once the core foundation idea is secure, because it adds the detail that pushes answers higher.
🎓 Higher Tier: Inertial Mass
Inertial mass is defined as the ratio of force to acceleration: m = F/a. It measures how difficult it is to accelerate an object — its resistance to change in motion.
This is distinct from gravitational mass (determined by how strongly gravity attracts an object), but the two are always equal — a fact so fundamental that Einstein built General Relativity on it (the equivalence principle).
At GCSE, you need to know that inertial mass can be determined experimentally by applying a known resultant force to an object and measuring its acceleration, then calculating m = F/a.
Practice questions for Newton's Laws of Motion
According to Newton's First Law, what happens to an object when there is no resultant force acting on it?
A spaceship is travelling through deep space far from any planets. The engines are switched off. Explain what will happen to the motion of the spaceship and why.