Question

a river flows due south with a speedof 2.0m/s.a man steers a motorboat across the river:his velocity relative to the river is 4.2m/s due east.the river is 800m wide.what is his velocity relative to the earth?

Answer 1

V = 2m/s[270o] + 4.2m/s[0o]

X = 4.2 m/s.
Y = -2 m/s.

tanA = -2/4.2 = -0.47619.
A =-25.46o = 25.46o South of East.

V = x/cosA = 4.2/cos(-25.46) = 4.65 m/s.