Newton's Laws

Force

Force - The cause of motion (what causes objects to move)

• Two types of force
  • pushes
  • pulls
• Forces are measured in Newtons
  • SI unit of force
  • Symbol N
  • Measured by using a spring scale
• Forces may be unbalanced or balanced

Balanced Forces - all forces acting on an object are equal

• there sis no change in motion

Unbalanced Forces - one or more forces acting on an object are stronger than others

• There is change in motion
  • A net force

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Newton’s Laws

• First Law - Inertia
• Second Law - Acceleration, Force & Mass
• Third Law - Action-Reaction

First Law

Inertia

• An object at rest (not moving) remains at rest unless acted on by an unbalanced force (push or pull)
• An object in motion remains in motion unless acted on by an unbalanced force (push or pull)

Inertia & Mass

• Mass is the amount of matter in an object

• The more mass an object has, the more inertia the object has

• Bigger objects are harder to start and stop

  

Second Law

Acceleration & Mass definitions

• Acceleration is a change in velocity (speed or direction)
• Mass is the amount of matter in an object

Acceleration & Force

• The more force placed on an object, the more it will accelerate (change its motion)

Acceleration & Mass

• The more mass (or inertia) an object has, the more force it takes to accelerate the Object

  

Third Law

Action - Reaction

• Forces are always produced in pairs with opposite directions & equal strengths

• For every force there is an equal and opposite force

• Newtons cradle is an example of this law in practice