Free-Body Diagrams

Lab Brief #5

🎯 Your mission

Understand the idea. Then look for it everywhere.

⚡ The twist

Energy never disappears — it just hides somewhere else.

What you'll learn

A free-body diagram shows one object as a dot with every force on it drawn as an arrow from that dot. Arrow length shows size and direction shows line of action. Getting the diagram right usually solves the problem before any arithmetic starts.

Key words

free-body diagram
A sketch showing all forces acting on a single chosen object.
normal force
The push a surface exerts perpendicular to itself on an object resting on it.

Make a hypothesis first

Before you start: which will move faster, and why?

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

Step 1 of 4 · Read

Think about what you just learned: say what "free-body diagram" and "normal force" mean in your own words before you start.

Step 2 of 4 · Do

Draw free-body diagrams for four cases: a book on a table, a box being dragged at constant speed, a ball at the top of its flight, and a car braking. Label every arrow with its cause and mark which pairs balance.

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

On a free-body diagram you draw forces acting:

How sure are you?😐 maybe

Question 2 of 2

A book rests on a table. The normal force acts:

How sure are you?😐 maybe

Mind = blown

🎢 You feel weightless on a roller coaster because you and the seat are falling at the same speed.

Nice work!

You got 0 of 2 right.

Next: Friction: Static, Kinetic, and Useful All lessons

🎯

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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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