Question

Could someone please hep me with this kinematics question?:

A swimmer heads directly across a river, swimming at 1.6 m/s relative to the water. She
arrives at a point 40 m downstream from the point directly across the river, which is 80 m
wide.

a) What is the speed of the river current?

b) What is the swimmer's speed relative to the shore?

c) In what direction should the swimmer head to arrive at the point directly opposite her
starting point?

d) How long would it take to cross the river swimming in the direction found in (c)?

Answer 1

I need three known variables to find the fourth one but I don't have three because the velocity of the water current is unknown (in fact part of the question is to find that). I attached what little work I was able to do (which is basically just drawing the problem and listing the equations).

Answer 2

You can start to find out the answer for the first part by dividing the width of the river by the speed of the swimmer ie 50 seconds. In that time, our swimmer drifts 40m downstream so I'd say the flow was 40m/50s so 0.8m/s.

You can use Pythagoras squares to figure out the distance swum is 89 m. The angle needed comes from the triangle too: use tangent of the angle ie opposite (40m) divided by adjacent (80m) is 0.5. This gives an angle of 26.6 degrees upstream. Hope this helps.

Answer 3

Rsin@ is velo of water

Answer 4

Thanks guys.