Newton’s Laws of Motion

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Slide 1

While most people know what Newton's laws say, many people do not know what they mean (or simply do not believe what they mean).

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Newton’s Laws of Motion

1st Law – An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force.

2nd Law – Force equals mass times acceleration.

3rd Law – For every action there is an equal and opposite reaction.

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1st Law of Motion (Law of Inertia)

An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force.

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1st Law

Inertia is the tendency of an object to resist changes in its velocity: whether in motion or motionless.

These pumpkins will not move unless acted on by an unbalanced force.

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1st Law

Once airborne, unless acted on by an unbalanced force (gravity and air – fluid friction), it would never stop!

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1st Law

Unless acted upon by an unbalanced force, this golf ball would sit on the tee forever.

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Why then, do we observe every day objects in motion slowing down and becoming motionless seemingly without an outside force?

It’s a force we sometimes cannot see – friction.

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Objects on earth, unlike the frictionless space the moon travels through, are under the influence of friction.

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There are four main types of friction:

Sliding friction: ice skating

Rolling friction: bowling

Fluid friction (air or liquid): air or water resistance

Static friction: initial friction when moving an object

Friction!

What is this unbalanced force that acts on an object in motion?

Slide 10

Slide a book across a table and watch it slide to a rest position. The book comes to a rest because of the presence of a force - that force being the force of friction - which brings the book to a rest position.

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