## Materials

• 12 playing cards
• Scotch tape
• A small cardboard platform (the bottom of a milk or juice carton works great, or you can cut down a pizza or cereal box)
• And something small to use as your weights, like pennies or paper clips

## Instructions

1. Identify the Problem
The most critical step of any engineering challenge is to understand the problem you are trying to solve:
• Using only 12 playing cards, how can you design a flat-topped structure that supports as much weight as possible without collapsing?
• You will need to think like a civil engineer to figure out the critical load. This is the amount of weight or force that causes a structure to fail or fall apart.
2. Brainstorm Designs and Build
• Spend a few minutes trying out different arrangements of cards to get ideas for which design would work best.
• As you build, see how much tape you need to secure your structure. You can use all 12 cards, but you don’t have to.
3. Test Your Design
• It’s time to test the strength, also known as the structural integrity, of your house! Will your house stay up when weight is added?
• When you are ready, place your cardboard platform on top of your structure and count how many pennies you can add, one at time, until it collapses.
• Be sure to add weight evenly. If your house falls down after only a few pennies, that’s OK. This is why testing is so important.
• How many pennies did it take for your structure to fail? Record the total number of pennies as your critical load.
• Or you can calculate the critical load in grams. A US penny weighs 2.5 grams.
4. Evaluate and redesign
• Think about any changes you would like to make using these questions:
• How much weight did the house support? Could it be designed to support more?
• Where is your structure failing? How can you strengthen the weak points?
• Did the height of your card structure affect its ability to support the added weight?
• What was the shape of your card structure? Is there another shape you can try?
5. Make Changes and Try Again!
• Redesign your house and test again.
• Were you able to increase the critical load?
• Looking for another challenge? Increase the difficulty by building without tape or by using index cards instead of playing cards.
6. Share Your Results with a teacher, parent/guardian, or DiscoverE!
• You can email photos to DiscoverE at social@DiscoverE.org or post on Instagram/Twitter using the hashtag #DiscoverEChallenge

Activity courtesy of IEEE TryEngineering.org. All rights reserved.

https://www.ieee.org/documents/critical_load_english.pdf

Supplemental content adapted for Dream Big Activities by the Carnegie Science Center.