Final answer:
Positive acceleration indicates an increase in velocity, meaning the car is speeding up. Claire's average running speed was 5 miles per hour, as she ran 20 miles in 4 hours.
Step-by-step explanation:
When a car has positive acceleration, this means that its velocity is increasing over time. In other words, the car is speeding up. If the acceleration is consistent and positive, the car's speed will continue to increase at a steady rate. For example, if a car's velocity increases from 10 m/s to 30 m/s in a span of 5 seconds, this change in velocity indicates that the car has been accelerating. A negative acceleration (or deceleration), on the other hand, would mean that the car is slowing down, as its velocity is decreasing. Claire's average speed can be calculated by dividing the total distance traveled by the total time taken. Since she ran 20 miles in 4 hours, her average speed would be 20 miles / 4 hours = 5 miles per hour. This is the average speed because it assumes a constant rate over the entire distance.