A boat crosses a 200m wide river at 3m/s, north relative to water. The river flows at 1m/s as shown. What is the velocity of the boat as observed by a stationary observer on the river back from the boat departed?

The resultant velocity = 3.16 m/s

Explanation:

Since the boat is moving North of the direction of the riverflow, the river would either be flowing westward or Eastward. The two motions form a right angle triangle with the resultant velocity being the hypotenuse of the traingle.

The resultant velocity will be given as;

R² = B² + r²

Where B is the velocity of the boat and r is the velocity of the river

R² = 3² + 1²

R² = 10

R = √10 = 3.16 m/s

Therefore, the resultant velocity = 3.16 m/s