Position-time graph — Science definition
A graph of position versus time; its slope at any point is the instantaneous velocity.
Where it is taught
- Motion Graphs & Kinematic Equations — Motion & Kinematics, Physics & Environmental Science, Grade 12
In use
A position-time graph represents coordinates in a chosen frame.
Motion Graphs & Kinematic Equations
Questions using position-time graph
Problem 1
On a position-time graph, a horizontal (flat) line means the object is…
- moving at constant positive velocity
- speeding up
- at rest (not moving)
- moving backward
Answer and explanation
at rest (not moving)
A flat line has zero slope, meaning zero velocity — the object's position isn't changing, so it is at rest.
Problem 2
Describe how you would find (a) an object's velocity from a position-time graph and (b) its displacement from a velocity-time graph.
Answer and explanation
(a) Velocity is the slope of the position-time graph — pick two points on the line and compute rise over run (change in position divided by change in time). (b) Displacement is the area between the velocity-time line and the time axis; for simple shapes you find the area of the rectangle, triangle, or trapezoid the graph forms.
Problem 3
On a position-time graph, a flat horizontal line means the object is…
- moving backward
- moving at constant velocity
- at rest
- accelerating
Answer and explanation
at rest
Zero slope means zero velocity, so the object's position isn't changing — it is at rest.