5.13 Distance-time graphs
9 exam questions worth 22 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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What does a horizontal line on a distance-time graph show?
Choose one answer.
Correct Not quite: the answer is The object is stationary
Mark scheme
B: The object is stationary
Model answer
The object is stationary (B).
State what the gradient of a distance-time graph represents.
Mark scheme
speed
Model answer
The speed of the object.
On a distance-time graph, an object moves from 10 m to 70 m in 15 s. Calculate its speed.
Mark scheme
change in distance = 60 m (1); speed = 60 ÷ 15 (1); 4.0 m/s (1)
Model answer
Speed = (70 − 10) / 15 = 60 / 15 = 4.0 m/s.
Look at the distance-time graph in this lesson. Describe the motion of the object between 30 s and 40 s.
Mark scheme
the object moves back towards the start (1); it moves 60 m in 10 s (1); at a constant speed of 6 m/s (1)
Model answer
The object returns towards its starting point, covering 60 m in 10 s at a constant speed of 6 m/s.
Two objects are shown on the same distance-time graph. Line X is steeper than line Y. State which object is moving faster and explain how you know.
Mark scheme
X (1); the gradient is greater so the speed is greater (1)
Model answer
Object X is faster, because its line has a bigger gradient.
A student says that a downward-sloping line on a distance-time graph means that the object is slowing down. Explain why the student is wrong.
Mark scheme
the line shows that the distance from the start is decreasing (1); so the object is moving back towards the start, not necessarily slowing down (1)
Model answer
A downward line shows that the distance from the start is decreasing, so the object is moving back toward the start. It could be at constant speed.
Describe the shape of the distance-time graph for an object that starts from rest and speeds up, and explain why it has that shape.
Mark scheme
the graph is a curve that gets steeper (1); because the gradient / speed increases with time (1)
Model answer
The graph is a curve that gets steeper, because the gradient (the speed) is increasing.
(Higher) A tangent is drawn to a curved distance-time graph at 5.0 s. The tangent passes through (3.0 s, 4.0 m) and (7.0 s, 24.0 m). Calculate the speed of the object at 5.0 s.
Mark scheme
gradient = change in distance ÷ change in time (1); (24.0 − 4.0) ÷ (7.0 − 3.0) (1); 5.0 m/s (1)
Model answer
Speed = (24.0 − 4.0) / (7.0 − 3.0) = 20.0 / 4.0 = 5.0 m/s.
A student walks to school. She walks 600 m in 5 minutes, waits at a crossing for 1 minute, then walks 300 m in 2 minutes. Calculate her speed during each walking stage in m/s and sketch (describe) the distance-time graph.
Mark scheme
stage 1: 600 ÷ 300 = 2.0 m/s (1); stage 3: 300 ÷ 120 = 2.5 m/s (1); graph: straight line sloping up for 5 min (1); horizontal for 1 min (1); steeper straight line for the last 2 min (1)
Model answer
First stage: speed = 600 m / 300 s = 2.0 m/s. Last stage: speed = 300 m / 120 s = 2.5 m/s. The graph is a sloping straight line for 5 minutes, a horizontal line for 1 minute, and then a steeper sloping line for 2 minutes.
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