You are riding on a jet ski at an angle upstream on a river flowing with a speed

Question

You are riding on a jet ski at an angle upstream on a river flowing with a speed of 2.8 m/s. Suppose the jet ski is moving at a speed of 15 m/s relative to the water.
(a) At what angle must you point the jet ski if your velocity relative to the ground is to be perpendicular to the shore of the river?
What is the ° upstream

(b) If you increase the speed of the jet ski relative to the water, does the angle in part (a) increase, decrease, or stay the same?

Explain.

The answer for b is decrease. I only new this by calculating a. I got 11.4/11.5 degrees and it is still wrong.Anyone have any clue what I'm doing wrong?

Explanation / Answer

If you were to draw both of the vectors out with their respective angles, the vector sum of the vectors going upstream would give you the relative speed.

V(jet ski) = V(s1) cos(1) = (2.8)cos(35°) = 2.30 m/s

V(ground) = V(s2) cos(2) = (9.5)cos(20°) = 8.93 m/s

Speed of jet ski relative to water = V(jet ski) + V(ground)

= 11.23 m/s

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