Engineers are people who design and build things. They build bridges, buildings, and machines. Engineers must pick the right materials for every job.
A bridge needs to hold weight without falling. Most bridge parts are rigid so they stay strong and straight. But some bridges have flexible parts too! Flexible parts let a bridge move a little in strong wind. A little bending can stop a big break.
Today you are the engineer. You will build a small bridge between two books. You will test different materials. Which material holds the most weight? Make a guess, test it, and record what happens. That is exactly what real engineers do!
1. What does an engineer do?
2. Why do some bridges have flexible parts?
Ask a grown-up for help gathering materials. Use only light weights like coins or blocks. Keep small items away from little brothers and sisters.
You need: two stacks of books, paper, straws, cardboard, and coins for weights.
Steps: 1. Put the book stacks about 6 inches apart. 2. Lay one material across the gap like a bridge. 3. Add coins one at a time to the middle. 4. Count how many coins it holds before it bends down and drops them!
My guess: the strongest bridge material will be ______________________ .
Test each material. Record your results.
| Bridge material | How many coins did it hold? | Flexible or rigid? | Did it bend a lot? |
|---|---|---|---|
| One sheet of paper | YES / NO | ||
| Folded paper (fan folds) | YES / NO | ||
| Straws side by side | YES / NO | ||
| Cardboard | YES / NO |
1. Which bridge held the most coins? ______________________
2. Which bridge held the fewest coins? ______________________
3. How many more coins did the strongest hold than the weakest? __________
| Question | My answer |
|---|---|
| What was my guess? | |
| What really won? | |
| Was my guess right? | YES / NO |
Draw your strongest bridge with the coins on top. Label the material.
Why do you think the winning material held the most coins? Use the words rigid or flexible in your answer.
Pick your weakest bridge material. Can you make it stronger? Try folding it, rolling it, or doubling it. Test it again!
What I changed: ______________________________________
Coins it held before: __________ Coins it held after: __________
Did my change work? YES / NO
Write today's date in your journal. Then finish these sentences:
Today I built bridges out of ______________________________.
One thing I would try next time is:
Look for a real bridge when you ride in the car. What material is it made of? Tell a grown-up if you think it is rigid, flexible, or both!