Distance-Time Graphs

Distance-Time Graphs

Definitions

• A Distance-Time graph is a way of visually representing a journey.
• The horizontal x-axis typically displays the time elapsed, usually in seconds, minutes or hours.
• The vertical y-axis typically displays the distance travelled, usually in metres or kilometres.
• The gradient of the line in a distance-time graph represents the speed of the journey.

Straight Lines

• A straight horizontal line on a distance-time graph indicates that the object is stationary. It’s not moving because the distance remains constant over time.
• A straight line inclining upwards indicates steady motion. The object is moving at a constant speed.

Remark on Speed

• The steeper the incline of the line, the faster the speed of the object.
• The gradient of the line on the distance-time graph gives the speed of the object.

Curved Lines

• A curved line on a distance-time graph indicates that the object is accelerating or decelerating.
• If the curve slopes upwards and the gradient is increasing, the object is accelerating.
• If the curve slopes upwards but the gradient is decreasing, the object is decelerating.

Calculating Speed

• To calculate the speed using a distance-time graph, choose two points on the line, and divide the change in distance (vertical difference) by the change in time (horizontal difference). This will give you the average speed between these two points.

Interpreting the Graph

• Use the graph to understand the journey. Check for periods of stillness (horizontal lines), constant speeds (straight inclined lines) and acceleration or deceleration (curved lines).

Practice

• Try sketching distance-time graphs based on different scenarios for better understanding of the topic. Practice calculating speeds using different points from the graphs.