Fundamentals of Physics Extended (10th Edition)

Published by Wiley
ISBN 10: 1-11823-072-8
ISBN 13: 978-1-11823-072-5

Chapter 2 - Motion Along a Straight Line - Problems: 4


44.4 km/hr

Work Step by Step

To find the average speed we need to find the total distance and divide it by the total amount of time traveled. The question states that the car goes up the hill at 40 km/h and back down the hill at 60 km/h. We do not know the height of the hill or the distance traveled, but we know that the car must travel the same distance going up the hill as it does down the hill. We will assume that this distance is 100 km. To find the time it takes for the car to travel up the hill, we take the 100km and divide it by 40 km/h. This gives us 2.5 hrs. To find the time it takes for the car to travel down the hill, we take the same 100 km and divide it by 60km/h. This gives us 2 hours. Therefore, the car traveled a total of 200 km (100km up and 100 km down) and it took a total of 2.5hrs + 2 hrs = 4.5 hours. Taking the total distance and dividing by the total amount of time we get 200km / 4.5 hours = 44.4 km/hr
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