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Practical Physical Science

Lesson 7-4 Laws of Motion

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Objectives

  • Explain what is meant by a force.
  • Define and explain friction.
  • Explain and apply the three laws of motion.

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First Law of Motion

An object in motion remains in the same motion and an object at rest remains at rest unless a force acts on it.

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Friction is a force.

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Inertia

Inertia is the tendency of an object to resist changes in its motion.

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Newton’s Second Law of Motion

The amount of force needed to change an object’s motion depends on its mass.

Force = Mass x Acceleration

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Newton’s Third Law of Motion

If an object exerts a force on a second object, the second object will always exert a force on the first object.

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Practice

Lesson 7:4 Review p. 195

WB 33 “The Laws of Motion”

Which way will the skateboard go if the fire extinguisher is released?