Position-Time Graphs

Lesson 3 of 10 · 7 min · Free, no account needed

What you will learn

A position-time graph puts time across and position up: the whole trip in one line.
Flat means standing still. Steep means moving fast.
The slope of the graph is the speed: rise ÷ run gives metres per second.

Your fitness app drew your walk to school. When did you stop to chat?
Up means further from home, across is time. Tap the piece where you think you stood still.
Walk, and the graph draws itself.
Drag the walker along the street for 30 s. Stop for a bit, then hurry.
Now the other way: draw a walk with a stop in it.
Draw the graph from left to right. Then the walker acts it out.
Steepness has a name you know from math.
A position-time graph: time across, position up. Each point says where you were at that moment.
Flat means standing still. Steeper means faster: the runner's line climbs twice as fast.
The slope is the speed: rise ÷ run. The walker goes 6 m in 4 s, and 6 ÷ 4 = 1.5 m/s.
The bus stop is 90 m away and the bus leaves at 60 s. What is the slowest pace that makes it?
Turn the dial: it sets the slope of your line. Make the line hit the bus stop point.
Game: copy the walk.
Act out each dashed graph by moving the walker. Match 75 or more on all three.
From math class: a taxi's price graph. How much does each km add?
Drag the marker on the scale. In math this steepness is the slope; in physics, on a position graph, it is the speed.
Which graph means: fast to school, a wait, then slowly back home?
Up is distance from home, across is time.
Your walk from the start of the lesson, one more time.
Press Play and watch the dot ride your graph.

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