Newton's laws of motion
Key points
- When no forces act on a body, then it moves with constant velocity
- If body A exerts a force on body B, then body B will exert an equal but opposite force on body A
- The net force on a body of constant mass is proportional to that body’s acceleration
Newton’s second law (law of Inertia) states: When the net force on a body is zero, the body will move with constant velocity (which may be 0).
Force definition: A force is what changes a body’s velocity.
- Inertia keeps the body in the same state of motion when no force acts on the body
Formula Booklet
Newton’s second law of motion states: The net force on a body of constant mass is proportional to that body’s acceleration and is in the same direction as the acceleration.
- Unit of force: newton (N)
- One newton is the force required to accelerate a mass of 1kg by 1ms-2 in the direction of the force
Newton’s third law of motion: If body A exerts a force on body B, then body B will exert an equal but opposite force on body A.
- Those forces are known as force pairs
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