Your vessel is on course 135°T, speed 18 knots. From the appearance of the sea you estimate the speed of the speed of the true wind as 24.5 knots. The apparent wind is 40° on the starboard bow. Determine the speed of the apparent wind.
Given: Own speed = 18 knots
True wind speed = 24.5 knots
Apparent wind Angle = 40°
What is asked: Apparent wind speed
Solution: Own speed² + True wind speed² + 2 x Own speed x True wind speed x Cos 40° and then square root the answer to get the apparent wind speed. This the formula for apparent wind speed:
Apparent wind speed = √18² + 24.5² + 2 x 18 x 24.5 x Cos 40° = 39.99 knots
Well, as you notice, there's a little discrepancy if we are going to compare our computed answer with the official answer which is 36.0 knots. So what shall we do? My instructor during my review used to advice us to choose the nearest answer in cases like this. That is to select the best answer, so to speak.
This is very problem taken from my reviewer book.
Feel free to comment.
See Related Problem
Given: Own speed = 18 knots
True wind speed = 24.5 knots
Apparent wind Angle = 40°
What is asked: Apparent wind speed
Solution: Own speed² + True wind speed² + 2 x Own speed x True wind speed x Cos 40° and then square root the answer to get the apparent wind speed. This the formula for apparent wind speed:
Apparent wind speed = √18² + 24.5² + 2 x 18 x 24.5 x Cos 40° = 39.99 knots
Well, as you notice, there's a little discrepancy if we are going to compare our computed answer with the official answer which is 36.0 knots. So what shall we do? My instructor during my review used to advice us to choose the nearest answer in cases like this. That is to select the best answer, so to speak.
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| Apparent wind speed |
This is very problem taken from my reviewer book.
Feel free to comment.
See Related Problem