You are riding on a Jet Ski at an angle of 35¢ª upstream on a river flowing with a speed of 2.8 m/s. If your velocity relative to the ground is 9.5 m/s at an angle of 20.0¢ª upstream, what is the speed of the Jet Ski relative to the water? (Note: angles are measured relative to the x axis)

Answer 1

Use the VECTOR equation
Vwater + Vski/water = Vski/land
Vski/water is the velocity of the Jetski with repect to water, etc..
Vwater is the velocity of the water. Let x be the upstream direction and y be the cross stream direction.
Vwater,x = 2.8 m/s
Vwater,y = 0
Vski/land,x = 9.5 cos 20 = -8.93
Vski,land,y = 9.5 sin 20 = 3.25

Vski/water,x = -8.93 - 2.8 = -11.73 m/s
Vski/water,y = 3.25 m/s

Answer 2

13m/s