The speed of the river flow is 1 m / s, the speed of the rower’s movement relative to the water is 1.5 m / s.

The speed of the river flow is 1 m / s, the speed of the rower’s movement relative to the water is 1.5 m / s. What is the minimum time (s) for a rower to be able to cross by boat to the opposite bank of a 150m wide river?

In a minimum time, you can cross if the rower moves 90 degrees relative to the water. If you draw a drawing (from the total vector of vectors through t. Pythagoras, you can find the speed), then:

V ^ 2 = V1 ^ 2 + V2 ^ 2
V ^ 2 = 1.5 * 1.5 + 1 = 3.25 (m / s)
V = 1.80 (m / s)

Suppose that the swimmer stood still at time t = 0, then
V0 = 0 m / s

Using the formula for the path without acceleration, we find the time:
S = (V + V0) t / 2

t = 2S / V
t = 167 s

Answer: t = 167 s