Imagine a toy car rolling off the same ramp onto four different floors: carpet, wood, sandpaper and tile. Which floor do you think will stop it soonest?

Today we will find out fairly, and we will measure with real care.

Look at the four surfaces: carpet, wood, sandpaper and tile. Whisper to your partner which one you think will make the car roll the shortest distance, and say why. Then we will share a few ideas with the class.

We will plan a fair test so that only one thing changes. Five cards will come up for sorting, and your job is to call out where each one belongs: Change, Measure, or Keep the same.

Then work with your group, in this order:

• First, set your ramp on two identical books so that it is at the class height shown on the board, and mark one start line, because every run today has to begin from the same place.
• Next, visit the shared surface stations in the order your group chose, changing only the surface under the car.
• At each surface, release the same car from the same start three times with no push, so that the only thing moving the car is the ramp.
• Measure each time from the start line to the front of the car in centimetres. The ramp part is the same every run, so a shorter total still means that surface slowed the car more.
• Before you move on, put the three distances in order — shortest, middle, longest — and write the middle number on your Investigation Journal.

You should already have three distances and a middle value for each surface you finished on your Investigation Journal from the runs.