Reading Motion Graphs — Drills · Grade 8 Science

Chapter: Motion

What these drills covers

By the end of Reading Motion Graphs you should be able to:

6 questions, numeric, written answer and multiple choice, each with a worked explanation.

Vocabulary used: position, slope, average velocity, model, evidence, system boundary, assumption.

Problem 1

Position changes from 12 m to 4 m in 2 s. Find average velocity.
Answer and explanation

-4 m/s

(4 − 12) ÷ 2 = −4.

Problem 2

Why read the axis labels before interpreting a graph?
Answer and explanation

A horizontal position–time line means rest; a horizontal speed–time line can mean constant nonzero speed.

Problem 3

On a distance-time graph, a horizontal line means the object is
  1. speeding up
  2. stationary
  3. moving at constant speed
  4. reversing
Answer and explanation

stationary

Distance is not changing, so the object is at rest.

Problem 4

A distance-time graph rises from 0 m to 60 m over 12 s in a straight line. What is the speed in m/s?
Answer and explanation

5 m/s

The gradient is 60/12 = 5 m/s.

Problem 5

On a speed-time graph, a horizontal line above zero means
  1. the object is stationary
  2. constant speed
  3. constant acceleration
  4. the object is reversing
Answer and explanation

constant speed

Speed is unchanging, so there is no acceleration.

Problem 6

Explain how to tell acceleration from constant speed on each kind of graph.
Answer and explanation

On a distance-time graph constant speed is a straight sloping line and acceleration is a curve that gets steeper. On a speed-time graph constant speed is a horizontal line and acceleration is a sloping one. The same motion looks different on the two graphs, so the axes must be read before interpreting the shape.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

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