Area accumulates rate over time: (metres/second) × seconds gives metres. A horizontal velocity graph can have nonzero area despite zero slope. Area below zero contributes negative displacement.

The model has a domain of validity. Explain its assumptions before using it in a changed context, then compare your prediction with evidence.

• On position-time graphs slope is velocity. On velocity-time graphs slope is acceleration and signed area is displacement.
• A horizontal line on a velocity graph does not mean rest unless it lies at zero velocity.