Velocity Has a Direction

Lesson 4 of 10 · 7 min · Free, no account needed

What you will learn

Distance is every metre you travel. It only grows.
Displacement is where you end up compared with where you started: end minus start, with a sign. Back home means 0.
Velocity is speed with a direction: plus to the right, minus to the left. On a position-time graph, a falling line means negative velocity.

You run one lap of a 400 m track and finish where you started. How far did you go?
Careful.
Drive the car both ways. Watch the two counters.
Zero is in the middle: right is plus, left is minus. Go past zero on both sides.
Play three trips and watch their graphs.
What does a line going down mean?
Three numbers, three names.
Distance: every metre travelled, left or right. Here 30 + 40 = 70 m. It only grows.
Displacement: end minus start, with a sign. Here -10 - 0 = -10 m: 10 m to the left of the start.
Velocity: speed with a direction. Moving right it is plus, moving left it is minus, like -5 m/s.
Draw a 40 s walk with 100 m of distance and a displacement of 0.
Start at zero. The counters under the graph follow your pen.
Game: delivery drone. Three parcels, one battery.
Tap a house to fly there. Deliver all three and land back at base before the battery dies.
Code: make the car drive left with a negative velocity.
The car starts at 10 m. Each turn of the loop is one second. It should end at 0.
Tap every piece of this trip where the velocity is negative.
Zero is in the middle of the track. Tap a piece again to undo.
Your drone route against the shortest one.
Press Fly both and compare the batteries.

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