# Question on Physics

1. Nov 23, 2009

### vu95112

I read one book. The author says that, in the old day, people know to apply physics to lead a boat against the wind. Anyone can help me on this question. What is the law in physics do they apply? Thank You.

2. Nov 23, 2009

### FoxCommander

This i believe has to do with aerodynamics. A sail works just like an airplane wing, if you point the boat against the wind, the sail will have a curve like an airplane wing. Lets say that this bulge is towards the left. So air will flow faster at the left side and slower at the other because it has to travel a greater distance to get to the other side. Just like an Airplane wing(i know i keep repeating this but its exactly the same principle). So the air going faste will have less pressure than the slower moving air. And so if you take the pressure difference and multiply it times the area of the sail you will see that the force will actually push it forward against the wind.
If this doesnt make sense look at my diagram i am about to submit
Sincerely,
FoxCommander

3. Nov 23, 2009

### FoxCommander

Sorry i couldnt get my scanner to work so just look it up on google and you should be able to make sense of it using my description

4. Nov 23, 2009

### vu95112

Hello FoxCommander,

Thank you very much for your help. I got it. I can search it on Google. I wish you have a very nice Thanksgiving.

Sincerely,

Vu95112

5. Nov 23, 2009

### FoxCommander

Thanks and you have a wonderful Thanksgiving yourself!

Sincerely,
FoxCommander