- Define and explain Distance–Time Graphs in your own words
- Use key terms such as speed accurately
- Apply what you have learned to new examples and questions
- Avoid the common mistakes learners make with this topic
This lesson focuses on Distance–Time Graphs: reading journeys from graphs and finding speed from the gradient.
Reading journeys from graphs and finding speed from the gradient.
Key ideas
Graphs turn journeys into pictures
On a distance–time graph, the gradient (slope) equals the speed — steeper means faster, flat means stationary. On a velocity–time graph the gradient gives acceleration, and the area under the line gives the distance travelled. One graph can replace a whole table of data.
Speed tells you how fast, velocity tells you how fast and where to
Speed = distance ÷ time is a scalar with no direction. Velocity adds direction, making it a vector. Two cars can share a speed of 20 m/s yet have different velocities if they head opposite ways — and that difference matters in collisions.
Key term — speed: How fast something moves: distance travelled divided by time taken, measured in m/s or km/h.
On a distance–time graph, what does a flat horizontal section mean?
The object is stationary — distance is not changing as time passes.
Answer: The object is stationary — distance is not changing as time passes.
- Reading the gradient of a velocity–time graph as speed The gradient of a velocity–time graph is acceleration; speed is read straight off the vertical axis.
- Mixing up distance and displacement Distance is the total path travelled; displacement is the straight line from start to end — they match only on a straight one-way trip.
Practice
It equals the area under the graph, between the line and the time axis.
100 ÷ 12.5 = 8 m/s.
Yes — its direction is changing, so its velocity is changing, which means it is accelerating even though its speed is constant.
25 × 40 = 1000 m.
Quick check
Which of these best defines "speed"?
A van accelerates from 10 m/s to 22 m/s in 6 s. Find the acceleration.
- Distance–Time Graphs: reading journeys from graphs and finding speed from the gradient.
- Graphs turn journeys into pictures: On a distance–time graph, the gradient (slope) equals the speed — steeper means faster, flat means stationary.
- velocity: Speed in a stated direction — a vector, so 30 m/s north and 30 m/s south are different velocities.
- Watch out for: reading the gradient of a velocity–time graph as speed