← Back to course
Builder's Lab / Week 09 / Tuesday
2/6
Week 09 · Balloon Car

Tuesday

Air out, car forward
// A car pushed by balloon air
⏱ about 20 min

Tuesday: Air Out, Car Forward

Raven threads a string through a straw. She tapes on a balloon.

Rocket lets the balloon go.

Whoosh! Air rushes out the back. The balloon zips forward along the string.

"What do you notice about the two directions?" Raven asks.

Nova draws two arrows. "I found a pattern!"

Push back, go forward

Air rushes out of the back of the balloon.

That pushes the balloon the other way, forward.

This forward push is called thrust.

Air goes...Balloon goes...
BackwardForward

Friction matters too

Wheels and axles rub as they turn.

Rubbing makes friction, and friction slows the car.

Wheels that spin freely help the car go far.

Watch it
A grown-up blows up a balloon.
They let it go in an open room.
Which way does the air go? Which way does the balloon go?
Safety first
Children under 8 can choke on balloons that are flat or broken.
A grown-up blows up every balloon.
Throw away broken balloon pieces right away.
Skip balloons if anyone has a latex allergy.
PUSH CHECK
  • Read the question.
  • Tap your answer.
Air rushes out the back. Which way does the balloon go?
What do we call the forward push?
IdeaTrue or false?
Friction can slow a balloon car.?
The air and the balloon go the same way.?
Wheels that spin freely help a car go far.?
WHY THIS EXERCISEGood thrust and low friction help a balloon car roll far.

Two forces on the car

  • Thrust: balloon air pushes the car forward.
  • Friction: rubbing parts slow the car down.
  • More thrust and less friction help the car go far.
THRUST AND FRICTION
  • Read the question.
  • Tap your answer.
Raven's balloon zips along the string. Which force moves it?
Wheels rub on the car. Which force is that?
What helps a car roll far?
Air rushes out the front of a balloon. Which way does it go?
THE STRING BALLOON
  • Tap a card.
  • Then tap its spot.
1First
2Next
3Then
4Last
Try it
Roll a toy car across the floor.
Now hold one wheel so it cannot turn.
Roll it again. What changed?
Safety first
Roll the car gently, away from people.
IdeaTrue or false?
A wheel that cannot turn makes more friction.?
Thrust pushes the balloon backward.?
A grown-up blows up every balloon.?
WHY THIS EXERCISEThrust moves the car. Friction slows it.
Draw the balloon and two arrows. Show where the air goes and where the balloon goes.

You know how balloon cars move!

Tomorrow, we build version 1.

← Monday