← Back to course
Builder's Lab / Week 04 / Thursday
4/6
Week 04 · Bridge the Gap

Thursday

Why did it sag?
// A paper bridge that holds the most coins
⏱ about 20 min

Thursday: Why Did It Sag?

Plink! Rocket's flat bridge sags to the table at coin three.

"Only two coins," Rocket says with a laugh. "We can improve it!"

Raven bends down to look. "What do you notice? It is flat."

Nova blinks twice. "Would you like a hint? Remember Tuesday's fan."

VersionShapeCoins held
Rocket version 1Flat sheet2

Find the problem

The flat sheet bent as soon as coins went on.

It held only two coins.

The crew will change one thing: the shape of the paper.

READ THE TABLE
  • Read the question.
  • Tap your answer.
How many coins did version 1 hold?
WHICH TEST IS FAIR?
  • Read the question.
  • Tap your answer.
The crew folds the paper. What must stay the same?
Rocket wants to fold it AND use thick cardboard. Is that fair?
PLAN THE FAIR TEST
  • Tap a card.
  • Then tap its spot.
1First
2Next
3Then
4Last
Draw your folded bridge plan.

A good guess

Engineers make a guess before they test.

Raven guesses the folded bridge will hold more coins.

Her reason: the folds made paper stiff on Tuesday.

Friday's test will check her guess.

THINK IT THROUGH
  • Read the question.
  • Tap your answer.
Which coin made version 1 touch the table?
What is Raven's guess?
What will the crew change?
IdeaTrue or false?
Rocket was sad about his flat bridge.?
A guess needs a reason.?
The crew will use new coins on Friday.?
WHY THIS EXERCISEGood guesses and fair tests help engineers learn.

You spotted the problem and planned a fair fix!

Tomorrow, we test version 2.

← Wednesday