Newton's First and Second Laws

This lesson covers Newton's first law and Newton's second law of motion as required by AQA GCSE Combined Science Trilogy (8464), section 6.5.3. These laws link forces to the motion of objects and form the backbone of the Forces topic.

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Newton's First Law

Newton's first law: An object at rest remains at rest, and an object in motion continues to move at a constant velocity, unless acted upon by a resultant (net) force.

In plain language:

• If the resultant force on an object is zero, the object either stays still or keeps moving at the same speed in the same direction.
• If the resultant force is not zero, the object will accelerate (change its velocity).

What Is Inertia?

Inertia is the tendency of an object to resist a change in its state of motion. The more massive an object, the greater its inertia and the harder it is to change its motion.

• A stationary object with high inertia (large mass) requires a large force to start it moving.
• A moving object with high inertia requires a large force to stop it or change its direction.