Year 9 Science · Unit 4 · Lesson 13
Challenge Worksheet
Learning Goals
Two objects on the same graph
Study the graph below showing Objects A and B on the same distance-time axes. Answer the questions that follow.
1. At t = 12 s, which object has travelled further? How can you tell from the graph without measuring?
2. What does the crossing point at t = 8 s represent physically? What is not the same at the crossing point?
3. Object B's line is curved and getting steeper over time. What does this tell you about its speed? How is this different from Object A?
Design challenge — bushwalker journey
A bushwalker leaves camp, walks 3 km at 4 km/h, stops for lunch for 30 minutes, then walks 2 km back toward camp at 3 km/h. Design a complete description of the distance-time graph for this journey.
(a) Calculate the time taken for each segment. Show your working using time = distance ÷ speed. Then complete the table.
| Segment | Distance | Speed | Time (show working) |
|---|---|---|---|
| Walk out | 3 km | 4 km/h | |
| Lunch stop | 0 km | 0 km/h | 30 min |
| Walk back | 2 km | 3 km/h |
(b) Describe what each segment looks like on the distance-time graph. Include the shape of each line and whether the slope goes up, stays flat, or goes down.
(c) What would be different if you drew this as a displacement-time graph instead of a distance-time graph? Explain why the final value on the two graphs would differ.
Wrap Up
In one sentence, what was the main idea of this lesson?