A river flows due south with a speed of 5.00 m/s. A man steers a motorboat across the river; his velocity relative to the water is 4.00 m/s due east. The river is 780 m wide. Part A What is the magnitude of his velocity relative to the earth

6.4 m/s

Explanation:

From the question, we are given that

Speed of the river, v (r) = 5 m/s

velocity relative to the water, v (w) = 4 m/s

Width of the river, d = 780 m

The magnitude of his velocity relative to the earth is v (m)

v (m) can be gotten by using the relation

[v (m) ]² = [v (w) ]² + [v (r) ]²

[v (m) ]² = 4² + 5²

[v (m) ]² = 16 + 25

[v (m) ]² = 41

v (m) = √41

v (m) = 6.4 m/s

thus, the magnitude of the velocity relative to earth is 6.4 m/s