Distance-time graphs (AQA GCSE Physics Combined Science): Revision Notes

Distance-time graphs

What are distance-time graphs?

Distance-time graphs are a way to show how an object moves. They help us see how far something has travelled over a period of time.

Reading distance-time graphs

The shape of the line tells us what type of motion is happening:

Constant speed

• Straight diagonal line
• The object moves at a steady speed
• The steeper the line, the faster the speed

Accelerating (speeding up)

• Curved line that gets steeper
• The object is moving faster and faster
• The distance covered increases more quickly over time

Decelerating (slowing down)

• Curved line that gets flatter
• The object is moving slower and slower
• The distance covered increases more slowly over time

Stationary (not moving)

• Horizontal flat line
• The object has stopped moving
• The distance stays the same

Calculating speed from distance-time graphs

To find speed, you need to work out the gradient (slope) of the line.

Formula: $\text{Speed} = \frac{\text{change in distance}}{\text{change in time}}$

Method:

1. Pick two points on the line
2. Find the change in distance (vertical difference)
3. Find the change in time (horizontal difference)
4. Divide distance by time

Average speed

To find average speed for a whole journey:

$\text{Average speed} = \frac{\text{total distance}}{\text{total time}}$

Key tips for exams

Remember!