TwiddleLab / Physics / How Things Move

Motion Is a Trail of Dots

Lesson 1 of 10 · 5 min · Free, no account needed

What you will learn

• Position is where something is along a line, measured from a fixed zero.
• A motion diagram marks the position at equal time steps, like a camera flash every half second.
• Same time between dots, so wide gaps mean fast, tight gaps mean slow, and dots on top of each other mean stopped.

Start the lesson

How the lesson goes

1. A camera flashes every half second as a skater rolls by. Where will she be at 2 s?

   Three flashes so far. Drag the yellow flag to your guess.

2. Now you are the skater. Drag her to the finish.

   A flash drops a dot every half second. Go fast, go slow, stop for a moment, and watch the dots.

3. A snail, a walker and a sprinter each left a trail. Who is who?

   One dot every second, for 5 seconds. Put each one on its trail.

4. What the dots show has names.

   Position: where the skater is along the track, measured from a fixed zero.

   A motion diagram: her position marked at equal time steps, here every 0.5 s.

   Same time between dots, so spacing shows speed: wide gaps fast, tight gaps slow.

5. Game: ghost race. Match each ghost's trail.

   Score 80 or more on all three ghosts. Your dot turns green when you are right on the ghost's dot.

6. Draw a trip in dots: speed up, stop, speed up again.

   Each dot is half a second after the one before. Then your skater rides it.

7. Race your trip against a sprinter.

   Both leave a dot every half second. Press Play.

Next lesson: Speed: Metres per Second · Part of the course: How Things Move

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