Monday
Monday: How Fast Is Fast?
Rocket sprints across the backyard and skids to a stop by the fence. "New record!" he shouts. "That was my fastest run ever."
Raven looks up from her notebook. "What do you notice about that claim? Fastest compared to what?"
Rocket frowns. "Compared to... yesterday? I think I was faster."
Nova drifts down from the tree, her light a soft cyan. "A feeling is not a measurement," she says. "What two things would you need to measure?"
Rocket thinks. "How far I ran. And how long it took."
"Then we need a start line, a finish line and a timer," Raven says. She tears off two strips of masking tape.
"Welcome to the Field," Rocket says, grinning. "Our backyard is now a physics lab."
Speed is distance divided by time
Speed describes how fast or slow an object moves. A physics text from OpenStax defines speed as the rate at which an object changes its location.
To find an average speed, divide the distance traveled by the time the motion took. That is the whole recipe.
Distance is the length of the path between where the object started and where it ended.
If Rocket runs 10 metres in 5 seconds, his average speed is 10 divided by 5. That is 2 metres per second.
A fast object covers a lot of distance in a short time. A slow object covers a little distance in the same time.
| Quantity | What it measures | Unit at the Field |
|---|---|---|
| Distance | How far the object moved | metres, with a tape measure |
| Time | How long the motion took | seconds, with a timer |
| Speed | Distance divided by time | metres per second |
- Read the question.
- Tap your answer.
Why "fastest ever" needs numbers
Rocket felt fast, but a feeling cannot be compared with yesterday. A number can.
Scientists write down the distance, the time and the speed. Then anyone can check the claim.
This week you will set up your own Field and start a Field Log. Every measurement you make goes in the log.
| Statement | True or false? |
|---|---|
| Speed is the rate at which an object changes its location. | ? |
| To find speed, you add the distance and the time. | ? |
| A fast object covers more distance in a given time than a slow one. | ? |
| A feeling of being fast counts as a measurement. | ? |
Put one strip of masking tape on the ground as a start line. Put another a few big steps away.
Write "Field Log, week 1" on a fresh page. Draw your two lines and label them.
A tape measure or ruler, a kitchen timer or phone stopwatch and masking tape are all that is needed.
The definitions come from an OpenStax physics text and the unit facts from NIST, which you can read at nist.gov.
Strong start. Tomorrow you will meet the units scientists everywhere share: the metre, the second and the kilogram.