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)

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