title: ‘Physics: Newton'’s Laws of Motion’ comments: true categories:

• General
• Science tags:
• General
• Science
• Physics date: 2019-11-12 11:49:52 math: true

## First Law: Inertia

An object in motion will stay in motion, and will maintain its speed and direction, unless acted on by an unbalanced force

• The principle of INERTIA is that all objects have a tendency to resist change in motion.
• An object with all forces balanced out will not change speed or direction until another force is applied to it.
• For example, a person sitting on a chair is being pulled down by gravity, but pushed up with an equal NORMAL FORCE. The person does not change speed or direction.
• If the person in the above example is in a moving car, which suddenly brakes, the person will continue to move forward until they are stopped by the seat in front of them: the person resists any change in motion until acted on by an external force (the seat in front)
• A more massive object therefore needs more force to reach the same acceleration as a less massive object.

## Second Law

Force is equal to mass times acceleration
• This is expressed mathematically as \(F=ma\)
• F: Force in Newtons (N)
• m: Mass in Kilograms (kg)
• a: Acceleration in Meters per Second squared \(m/s^2\)

## Third Law

Every Action has an Equal but Opposite Reaction
• The reaction force is known as the NORMAL FORCE
• The Normal force always acts perpendicular (at \(90^\circ\)) to the surface that your object is on
• The Normal force changes magnitude based on the force that it is attempting to balance

## Video: Newton’s Laws Crash Course (11 minutes)

##### Pranav Sharma
###### Site Owner

Year 12 Student, site owner and developer.