Answer:
- 4 km/h
- 0 km/h
- 1.5 km/h
Explanation:
You want John's speed on each section of the walk, given a graph showing the distance from home versus time.
Speed
The slope of a position versus time graph such as this one will give the velocity. A positive slope in this case represents a speed away from home. A negative slope represents a speed toward home.
Since we want speed, not velocity, the sign is of no importance. We are only concerned with the magnitude of change versus time.
Slope
The slope of the line in each section is its "rise" divided by its "run". It is useful to find grid point intersections where the line crossed, so that the rise and run are more accurately determined. The nature of the graph suggests that a "section of the walk" is one in which the speed has some constant value.
Section 1
The first section of the graph, from 0 to 1.5 hours, has a positive slope. It rises 6 km in that time, so the slope is ...
rise/run = (6 km)/(1.5 h) = 4 km/h
John's speed in the first section is 4 km/h.
Section 2
The change over the next half hour, the second section, is 0. John's speed in that section is ...
rise/run = (0 km)/(0.5 h) = 0 km/h
John's speed in the second section is 0 km/h.
Section 3
The change in distance over the last 4 hours is -6 km, so John's speed in the third section is ...
rise/run = (-6 km)/(4 h) = -1.5 km/h . . . . . . . velocity
John's speed in the third section is 1.5 km/h.
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Additional comment
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