A cyclist rides eastward for 60 km at a speed of 15 km/h, then immediately turns west and rides 30 km at a speed of 12 km/h. What is the cyclist’s total distance travelled and displacement from the starting point?
Answer
Total distance: 90 km; Displacement: 30 km east
The correct answer is Total distance: 90 km; Displacement: 30 km east — Step 4: State that the cyclist travelled a total of (90\text{ km}) and ended (30\text{ km}) east of the start.
Step-by-step solution
- Step 1: Identify two separate legs of the trip: east leg (60\text{ km}) and west leg (30\text{ km}).
- Step 2: Add the magnitudes to find total distance: (60+30=90\text{ km}).
- Step 3: Calculate displacement by subtracting westward distance from eastward distance: (60-30=30\text{ km}) eastwards.
- Step 4: State that the cyclist travelled a total of (90\text{ km}) and ended (30\text{ km}) east of the start.
Common mistake: adding westward distance as negative when calculating displacement
Concept tested: displacement versus total distance
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