Key Learning Objectives
- Distinguish between distance (scalar) and displacement (vector with direction).
- Calculate average speed using Speed = Distance ÷ Time (with unit conversions).
- Interpret distance-time graphs: stationary lines, constant speed gradients, and acceleration curves.
Topic Summary & Core Notes
Master motion vectors in Year 7 Physics. Distinguish between scalar distance and vector displacement, speed vs velocity, and calculate speed using Speed = Distance ÷ Time.
Key Rules, Formulas & Definitions
Speed Formula
Speed (m/s) = Distance (m) ÷ Time (s) [v = d / t]
Distance-Time Graph Gradient
Gradient = Rise ÷ Run = Distance ÷ Time = Speed of the object
Velocity Definition
Velocity = Displacement ÷ Time (Speed in a stated direction)
2 Step-by-Step Worked Examples
Worked Example 1
Worked Example 1: Distance vs Displacement on a Track
Question: An athlete runs once around a 400-metre circular track in 50 seconds, returning to the exact starting line. Calculate their total distance, displacement, and average speed.
Step-by-Step Solution:
- Step 1: Total distance: Total length of path travelled = 400 metres.
- Step 2: Displacement: Straight-line distance from start to finish = 0 metres (since they returned to start).
- Step 3: Average speed: Speed = Distance ÷ Time = 400 m ÷ 50 s = 8 m/s.
Final Answer: Distance = 400 m | Displacement = 0 m | Average Speed = 8 m/s
Senior Examiner Insight: Displacement is straight-line distance from starting point. Returning to start always gives 0 displacement.
Worked Example 2
Worked Example 2: Distance-Time Graph Analysis
Question: A horizontal flat line is shown on a distance-time graph for 20 seconds. What does this indicate about the object's motion?
Step-by-Step Solution:
- Step 1: Analyze gradient: Flat horizontal line has a gradient of 0.
- Step 2: Relate gradient to speed: Speed = gradient = 0 m/s.
- Step 3: Conclude: The object is stationary (at rest).
Final Answer: The object is stationary (not moving).
Senior Examiner Insight: Do not confuse a distance-time graph with a velocity-time graph (a flat line on a velocity-time graph means constant speed).
Common Pitfalls & Examiner Warnings
Common Mistake: Confusing flat lines on Distance-Time vs Velocity-Time graphs
On a distance-time graph, flat = stationary. On a velocity-time graph, flat = constant speed.
Common Mistake: Forgetting to convert minutes to seconds
Speed in m/s requires time in seconds (e.g. 2 minutes = 120 seconds).
Common Mistake: Ignoring direction when stating velocity
Velocity is a vector and must specify direction (e.g. '15 m/s North').
Interactive Self-Check Quiz (3 Questions)
Question 1 of 3
A cyclist travels 1,200 metres in 2 minutes. What is their average speed in m/s?
Click to Reveal Answer & Mark Scheme
Correct Answer: B) 10 m/s
Detailed Explanation: 2 minutes = 120 seconds. Speed = 1,200 m ÷ 120 s = 10 m/s.
Mark Scheme & Scoring Points: 1 mark for converting 2 mins = 120 s; 1 mark for 10 m/s.
Question 2 of 3
What does a steep straight diagonal line represent on a distance-time graph?
Click to Reveal Answer & Mark Scheme
Correct Answer: A) Fast constant speed
Detailed Explanation: A steep straight line has a high constant gradient, representing high constant speed.
Mark Scheme & Scoring Points: 1 mark for fast constant speed.
Question 3 of 3
Why is velocity classified as a VECTOR quantity?
Click to Reveal Answer & Mark Scheme
Correct Answer: B) It has both a magnitude (speed) AND a specific direction of travel.
Detailed Explanation: Vectors require both magnitude and direction.
Mark Scheme & Scoring Points: 1 mark for magnitude and direction.
Created by Fiaraz Iqbal
Former Headteacher & Senior Science / Maths Examiner
Fiaraz produces structured video walkthroughs, Tier 3 literacy packs, and exam mark scheme breakdowns to help secondary students achieve top grades.
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