Question

A North American river otter wants to cross the North Saskatchewan river. It can swim at a speed of 2.75 m/s. In that location, the distance directly across the river is 45.0 m and the current velocity is 2.5 m/s.
a) How much time does the otter take to get to the other side, if it points directly across the river?

b) How many metres downstream will the current have carried the otter when it gets to the other side?

c) Calculate the otter's velocity, relative to the bank from where it started.

Answer 1

Answer:

Step-by-step explanation:

time to cross will be the distance divided by the velocity in that direction.

a) t = d/v = 45/2.75 = 16.363636... 16.4 s

In the same time that the otter is swimming cross stream, the stream is also moving perpendicularly at its own pace.

b) d = vt = 2.5(16.36) = 40.9090... 40.9 m

As velocity is a vector, An observer on the bank would see the velocity as the vector addition of the cross stream and down stream velocities

c) v = √(2.75² + 2.5²) = 3.716517... 3.72 m/s  magnitude

  θ = arctan2.5/2.75 = 42.2736... 42.3° downstream of a line straight across