Newton's Third Law: Forces Come in Pairs

Lab Brief #3

🎯 Your mission

Run the experiment. Find out what really happens.

⚡ The twist

Speed isn't the same as force. Don't mix them up.

What you'll learn

If A pushes B, then B pushes A with an equal force in the opposite direction. The pair always acts on two different objects, which is why they never cancel out — a rocket pushes gas down and the gas pushes the rocket up.

Key words

action-reaction pair
Two equal and opposite forces acting on two different objects.
thrust
The forward force produced when an engine pushes exhaust backwards.

Make a hypothesis first

Guess: where does the energy go?

Say your guess out loud — then find out if you were right.

Get ready

🧰 What you need

wheeled chair
heavy ball
lighter ball
clear floor space

⚠️ Safety first

Work on a smooth clear floor away from stairs, with a spotter behind the chair.

Step 1 of 4 · Read

Think about what you just learned: say what "action-reaction pair" and "thrust" mean in your own words before you start.

Step 2 of 4 · Do

Sit on a wheeled chair holding a heavy ball and throw it forwards. Record which way you move and estimate the ratio of your speed to the ball's from your masses. Repeat with a lighter ball and compare.

Step 3 of 4 · Observe

Record what actually happened, including anything that did not match what you expected.

Step 4 of 4 · Record

Write a conclusion that answers the question this lesson opened with, and state your uncertainty.

Question 1 of 2

A rocket accelerates upwards because:

How sure are you?😐 maybe

Question 2 of 2

Action-reaction pairs never cancel because they:

How sure are you?😐 maybe

Mind = blown

⚡ Static electricity is the same physics as lightning, just smaller.

Nice work!

You got 0 of 2 right.

Next: Weight Is Not Mass All lessons

🎯

Next Smart Experiment

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✨ More to explore

🌍 Where you see this in real life: This is why airplanes can fly and why rockets reach space.

🏆 Stretch challenge (try it this week): This week, find one thing in your house that turns one kind of energy into another.

👨‍👩‍👧 For the dinner table: “Show me something at home that uses this kind of energy.”

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Newton's Third Law: Forces Come in Pairs

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