Fundamentals of Physics Extended (10th Edition)

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

Chapter 4 - Motion in Two and Three Dimensions - Problems: 70c

Answer

1km/h

Work Step by Step

The boat is moving upstream in the positive x direction at 14km/h and the water is flowing at 9km/h. Since the boat is moving upstream, it is traveling AGAINST the current, meaning that the river is flowing in the negative x direction. Therefore, to find the speed of the boat relative to the ground we need to subtract the two (opposite directions) which would be: 14km/h (speed of boat) - 9km/h (speed of water) = 5km/h in the positive x The child is then moving from front to rear on the boat (in the negative x direction) at 6km/h WITH RESPECT TO THE BOAT. The boat is moving 5km/h in the positive x and the child is moving -6km/h (in the negative x direction) relative to that, which gives -1km/h for the child's speed
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