Newton's Laws of Motion — The Big Three
Inertia, F = ma, and action–reaction — the three laws that explain all everyday motion.
By the PadhoDost Team · 📖 6 min read · Updated 4 August 2026
Part of JEE (Main + Adv) prep🧠 The seatbelt jolt
When a car brakes suddenly, your body lurches forward — it 'wanted' to keep moving. That's inertia, Newton's first law in action. The three laws together explain every push, pull and collision.
First law — inertia
A body stays at rest, or keeps moving at constant velocity, unless a net external force acts on it. Motion doesn't change on its own.
Second law — F = ma
The harder you push (more force) or the lighter the object (less mass), the greater the acceleration. This is the law you'll calculate with most.
Third law — action & reaction
Every action has an equal and opposite reaction. When you jump, you push the ground down and the ground pushes you up.
⚡ Quick check
A body of mass 2 kg has an acceleration of 5 m/s². The force on it is:
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