Newton's First Law — The Law of Inertia
Part of Newton's Laws of Motion — GCSE Physics
This key facts covers Newton's First Law — The Law of Inertia within Newton's Laws of Motion for GCSE Physics. Revise Newton's Laws of Motion in Forces for GCSE Physics with 13 exam-style questions and 15 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 2 of 15 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 2 of 15
Practice
13 questions
Recall
15 flashcards
📜 Newton's First Law — The Law of Inertia
Newton's three laws of motion: 1st Law (Inertia): an object stays at rest or moves at constant velocity unless a resultant force acts on it. 2nd Law (F = ma): the resultant force on an object equals its mass multiplied by its acceleration — double the force, double the acceleration; double the mass, half the acceleration. 3rd Law (Action–Reaction): every action has an equal and opposite reaction — when object A exerts a force on object B, object B exerts an equal force back on object A. These three laws together explain virtually all motion you will encounter in GCSE Physics.
Statement: An object remains at rest or continues moving at constant velocity unless acted upon by a resultant force.
What this means:
- Stationary objects stay stationary
- Moving objects keep moving in a straight line at constant speed
- Objects don't "naturally slow down" — they slow due to friction/air resistance
- Inertia = resistance to change in motion (depends on mass)
Keep building this topic
Read this section alongside the surrounding pages in Newton's Laws of Motion. That gives you the full topic sequence instead of a single isolated revision point.
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.
Quick Recall Flashcards
13 questions on Newton's Laws of Motion — practise free
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