Question

28 a motorboat can travel 6 mph in still water. the diagram shows a person on the bank of a river observing a motorboat aimed upstream. the person standing on the bank observes which motion of the motorboat? f the motorboat moves up the river at 6 mph. g the motorboat stays in the same place on the river. h the motorboat is pushed downriver by the water. j the motorboat will go 36 mph downriver if it turns around.

Explanation:

To determine the observed motion of the motorboat, we analyze the velocities: the boat's speed in still water is 6 mph upstream, and the river current is 6 mph downstream. These velocities are equal in magnitude and opposite in direction, so they cancel each other out. From the observer's perspective on the bank, the boat's net velocity is zero, meaning it appears to stay in the same place.

• Option F is incorrect because the current opposes the boat's upstream motion, so it doesn’t move up at 6 mph.
• Option H is incorrect as the boat’s upstream speed cancels the current’s downstream speed, so it isn’t pushed downriver.
• Option J is incorrect because if the boat turns around, its downstream speed would be \(6 + 6 = 12\) mph (not 36 mph), as it would add its still - water speed to the current’s speed.
• Option G is correct because the upstream speed of the boat (6 mph) and the downstream speed of the current (6 mph) result in a net velocity of \(6 - 6=0\) mph relative to the bank, so the boat seems to stay in the same place.

Answer:

G. The motorboat stays in the same place on the river.