- #1

fog37

- 1,402

- 95

- TL;DR Summary
- General expression of wind force on a sail...

Hello everyone,

In trying to better understand how sailboats work, how they can sail upwind (not directly), how the go faster than the wind speed, I have been thinking about the magnitude of the wind force and its equation: $$F_{wind}= \frac {1}{2} \rho_{air} A v_{wind}^2$$

Instead of ## v_{wind}##, would the correct expression for the wind force include the magnitude of the apparent wind speed, which should be the magnitude of the difference between the true wind velocity and the boat velocity?

In general, I believe the expression$$F_{air}= \frac {1}{2} \rho_{air} A v^2$$ is found in physics book as the magnitude of the air drag due to air and experienced by an object moving through air (zero wind speed).

Thanks!

In trying to better understand how sailboats work, how they can sail upwind (not directly), how the go faster than the wind speed, I have been thinking about the magnitude of the wind force and its equation: $$F_{wind}= \frac {1}{2} \rho_{air} A v_{wind}^2$$

Instead of ## v_{wind}##, would the correct expression for the wind force include the magnitude of the apparent wind speed, which should be the magnitude of the difference between the true wind velocity and the boat velocity?

In general, I believe the expression$$F_{air}= \frac {1}{2} \rho_{air} A v^2$$ is found in physics book as the magnitude of the air drag due to air and experienced by an object moving through air (zero wind speed).

Thanks!