Answers:
- Speed for section A = 15 km per hour
- Speed for section B = 0 km per hour
- Speed for section C = 60 km per hour
- Speed for section D = 40 km per hour
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Explanation:
To compute the speed, we divide the distance traveled over the time duration.
For instance, if a car goes 100 km in 5 hours, then its speed is 100/5 = 20 km per hour.
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For section A, the car travels 30 km over the course of 2 hours (since 11:00-9:00 = 2:00)
speed = distance/time = (30 km)/(2 hrs) = 15 km/hr
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We don't need to do any computations for section B. It's a flat horizontal line, so the speed is zero. There's no change in distance, so the car is stationary for this 1 hour period.
You could say speed = distance/time = 0/1 = 0 km/hr if you wanted.
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For section C, its change in distance is 60-30 = 30 km and the change in time is 0.5 hour (because it spans from 12:00 to 12:30)
So, speed = distance/time = (30 km)/(0.5 hr) = 60 km/hr
The steeper slope of section C, compared to section A, means the car is going faster.
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Section D spans from 12:30 to 14:00. This is a time period of 14:00-12:30 = 1:30 = 1.5 hours. The change in distance is 60 km
(60 km)/(1.5 hrs) = 40 km/hr
The speed of the car during section D is 40 km per hour.
Side note: if you were talking about velocities instead of speeds, then section D would have a negative velocity of -40 km/hr to indicate the car is going the opposite direction (compared to sections A and C). However, speed is always nonnegative.
