GCSE · Physics · AQA · Spec 8463
Newton's First Law
Physics · Forces
Newton's First Law — Forces and Motion
Compare three scenarios: what changes when the resultant force is zero vs non-zero?
Selected scenario
Book on a Table
Net force
Zero — forces are balanced
Motion
At rest
At rest. Balanced forces — the book stays exactly where it is.
Stop and Think
Read carefully — this is the most common exam misconception on this topic.
A train moves in a straight line at a constant speed of 50 m/s. The engine exerts a forward force of 8000 N. Which statement correctly applies Newton's First Law?
Zero Resultant Force — Constant Velocity
Both arrows are the same length — equal and opposite forces → zero resultant.
Tap a force to see what it does.
Higher tier: Inertia
Reason it through
Why does a more massive object resist changes to its motion more strongly?
First link · your turn
What property of an object determines how hard it is to start moving or stop it?
Relationship matrix
Tap any cell to reveal it. Tap a column header to read one property down every item.
Each cell hides a short answer and the reason behind it. Predict before you tap.
Cross-subject · Exam skill
AQA Command Words — Newton's First Law
Know what each command word is asking before you write a word.
01Definition
Give reasons or a mechanism — link the cause to the effect using physics.
02Mark-band signal
Usually 2–3 marks: name the resultant force, then link it to Newton's First Law and the resulting motion.
03Sentence stems
- Explain why a car moving at constant velocity has a resultant force of zero.
- Explain what would happen to the car's velocity if the driving force increased.
- Explain, using Newton's First Law, why passengers lurch forwards when a bus brakes.
04Common mistake
Describing what happens without saying WHY — 'the car keeps moving' scores zero; 'the resultant force is zero so Newton's First Law means velocity is unchanged' scores the mark.
WHAT YOU'VE LEARNED
A quick recap of today's lesson.
Zero resultant force means no change in motion — stationary objects stay still, moving objects keep going.
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