Newton's laws of motion

How it is used

The starting point of classical mechanics. Students refer to them by number: Newton's first law (inertia), second law (F = ma) and third law (action and reaction). In written solutions you 'apply' a law: 'Applying Newton's second law to the block gives...'.

Example sentences

1. Newton's laws of motion explain why passengers lurch forward when a bus brakes suddenly.

2. This week we'll apply Newton's laws of motion to blocks on inclined planes.

3. Newton's third law of motion says the rocket pushes the gas backwards and the gas pushes the rocket forwards.

Common collocations

• Newton's first law
• Newton's second law
• Newton's third law
• apply Newton's laws
• action and reaction

Related terms

• forceA push or a pull that can change how an object moves or change its shape. It has both size and direction and is measured in newtons (N).
• inertiaThe tendency of an object to resist any change in its motion, so it stays at rest or keeps moving with the same velocity. Objects with more mass have more inertia.
• net forceThe single force that has the same effect as all the forces acting on an object together. It is the vector sum of those forces and decides the object's acceleration.
• accelerationThe rate at which an object's velocity changes over time. It can mean speeding up, slowing down or changing direction, and it is measured in metres per second squared (m/s²).
• massThe amount of matter in an object, which also measures how hard it is to change the object's motion. It is measured in kilograms (kg) and does not depend on location.

More terms: Motion and Forces

• velocity
• gravity
• weight
• friction
• speed
• displacement
• equilibrium
• projectile motion
• torque
• centripetal force
• tension
• normal force