# Calculate vector forces on object being affected by wind

I am wondering how you calculate the vector forces of the wind on an object? The information I have is the bearing direction of the wind and the speed of the wind. So how do I calculate the x and y vector forces of the wind as shown in the diagram below? Also I do realise that using trig I can do a straight calculation but that only works out the speed not the force.

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The wind does not impart a 'force' on the object. The object does not 'feel' the wind (as long as it's not in contact with the ground). What actually happens is that the object moves concurrently with the wind in the same direction and with the same speed, in addition to the object's own velocity. So you have the object's velocity and the wind velocity; add them up and you get a net velocity, which is the true direction of travel.

From what is given, the angle that the velocity makes with the vertical is $$\theta=360^{\circ}-\text{Wind Bearing Angle}$$

The horizontal and vertical components of velocity are $$\cos (\theta)=\frac{W_y}{W}$$ $$\sin (\theta)=\frac{W_x}{W}$$ where $W$ is the net wind velocity.

You add the components of the wind speed to the object's speed to get the net velocity $$V_{x}=W_x+O_x$$ $$V_y=W_y+O_y$$

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Cheers Greg, that was my suspicion but wasn't entirely sure. It helped alot :) –  Nicholas Jun 22 '13 at 3:16
As far as I can tell, this answer contradicts itself. If the object travels with the same velocity as the wind (relative to the ground say) then it's completely unclear why $O_x$ and $O_y$ in your last two equations are not automatically zero. Moreover, it's absolutely not the case that flying objects always fly with the same velocity as wind (think for example of an airplane flying against a headwind). Wind does exert forces on objects unless those objects are in fact flying with precisely the same velocity as the wind, but this rarely happens. –  joshphysics Jun 22 '13 at 7:23
@joshphysics Do you know a better equation for this then? –  Nicholas Jun 22 '13 at 7:40
@Nicholas There is no way to solve this problem as it is written. The force of the air on a given object depends on the relative velocity of the object and the wind (among other things like its drag coefficient) neither of which have been specified. Is this the precise way the problem was initially stated? –  joshphysics Jun 22 '13 at 8:03
@joshphysics Yes there is, I am using this for a physics simulation for programming. I do have the information of the velocity of the object and have the information for the velocity of the wind. Any other information needed can be gotten if needed :) –  Nicholas Jun 22 '13 at 10:21