Which Design Works Better?

Imagine it is raining very hard outside. Water drips into a garden and makes a puddle on top of the soil. The plants don't like too much water sitting on them!

Two kids, Mia and Leo, each build a small rain cover to protect the plants. Mia makes hers with a flat piece of cardboard. Leo makes his with a folded piece of cardboard shaped like a little tent. They put each cover over a plant and wait for the rain.

After the rain, Mia's flat cover has a big puddle of water on top. Some water dripped right onto her plant. But Leo's tent-shaped cover let the water slide off to the sides! His plant stayed much drier.

• Which rain cover do you think worked better? Why?
• What is different about the two covers that might explain what happened?

When we want to solve a problem, we can design (that means plan and build) something to help. But how do we know if our design is good? We need to compare (that means look at two things side by side) and test them!

The Problem: A toy car needs to roll down a ramp and go as far as possible across the floor.

What you need:

• 🚗 A small toy car
• 📦 A flat piece of cardboard (Ramp A — smooth)
• 📦 A piece of cardboard with bumps or crinkles (Ramp B — bumpy)
• 📏 A ruler or piece of tape to mark where the car stops
• 📚 A stack of books to hold up the ramp

Steps:

• Stack the books and lean Ramp A (smooth) against them.
• Let the car roll down from the top. Mark where it stops on the floor.
• Now use Ramp B (bumpy) at the same height. Let the car roll down.
• Compare! Which ramp made the car go farther? Why do you think so?

When we tested the two ramps, we saw something important. The car went much farther on Ramp A (smooth) than on Ramp B (bumpy).

Why did this happen? The bumps on Ramp B slowed the car down. The smooth surface on Ramp A let the car roll fast and keep going.

Now here is the important part: we don't just say "Ramp A is better." We explain why by using what we saw in our test. We say: "Ramp A worked better because the smooth surface helped the car roll farther. The bumps on Ramp B slowed it down."

Here is a big idea that scientists and engineers use all the time: Structure and Function. That means the shape or structure of something helps it do its job (its function).

Let's see this pattern in different places!

Do you see it? In every example, the shape of the design helps it work well. When we compare designs, we look at how the shape or structure is different. Then we can explain why one works better!

People use comparing and explaining every day to make things better! Here are some examples:

Engineers are people who design and build things to solve problems. They always compare their designs and explain which works better. That is exactly what you are learning to do!

• Design — A plan you make to build something that solves a problem.
• Compare — To look at two or more things side by side and see how they are the same or different.
• Test — To try something out and see what happens.
• Explain — To tell why something happened using reasons or evidence.
• Structure — The shape or how something is built.