You are riding in a boat whose speed relative to the water is 6.9 m/s. The boat points at an angle of 25.0° upstream on a river flowing at 15.1 m/s. Find the time it takes for the boat to reach the opposite shore if the river is 26.5 m wide.

1 answer

It does not matter how fast the water is flowing. That just affects where on the opposite side you wind up.

Since the boat is moving at an angle of 25.0° upstream, the distance traveled is given by

26.5/d = cos 25.0°

divide the distance by the speed to get the travel time:

t = d/s = (26.5/cos25.0°)/6.9 = 4.23 s

Q: what the heck puny river is only 26.5m wide? That's barely a crick!