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Lesson · Grade 6 · Science

Newton's Third Law: Equal and Opposite Forces

  • Grade 6
  • Science
  • 1 min 10 s
  • British Columbia
  • BC6-SC-12

Someone steps off a small boat onto a dock. Their foot pushes the boat back, the boat pushes them forward, and the boat slides back while they step; a side panel then lays the two arrows together to show they are equal in size, point in opposite directions and act on different objects, so they do not cancel. The same pair of forces is then shown for a rocket and its hot gas and for a swimmer and the water, and the video ends on the recap "Forces come in pairs: equal and opposite."

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In one sentence

The question this lesson answers

When you push on something, does it push back?

Imagine stepping off a small boat onto a dock.

Transcript

What the lesson says

When you push on something, does it push back?

Imagine stepping off a small boat onto a dock.

As you step, your foot pushes the boat backward.

At the same time, the boat pushes you forward.

So you move forward onto the dock, and the boat slides back.

The two forces are equal in size.

And they point in opposite directions.

Each force acts on a different object, so they do not cancel out.

This is Newton's third law: forces always come in pairs.

A rocket pushes hot gas down and out of its engine.

The gas pushes the rocket up.

A swimmer pushes the water backward.

The water pushes the swimmer forward.

Forces come in pairs, equal in size and opposite in direction.

Curriculum

Where this fits

British Columbia, Grade 6

Science, Physics: Newton's three laws of motionBC6-SC-12

Previous: Newton's Second Law: Unbalanced Forces Cause AccelerationNext: Balanced and Unbalanced Forces in Sport and Play

The outcomes and strands follow the British Columbia curriculum.

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