# Quick 2D Motion Question (wind resistance)

1. Oct 4, 2012

### Vroc

1. The problem statement, all variables and given/known data
An airplane is flying 100m/s (N20E) according to the pilot, but is in a wind that is blowing 40 m/s (S10E). What is the plane's real velocity?

2. Relevant equations
Pythagorean Therom
Cosin and Sin Laws
Component Method

3. The attempt at a solution

Okay, I think I can easily get the answer if I know what this question is asking me. By real velocity, Does it mean the displacement from point 100 m/s (N20E) to 40 m/s (S20E)? Like, I can draw it on a graph and make the triangle. I would then calculate the angle and length of the unknown side. If that's not it, Then how would I go about getting it? Please Help me understand this.

2. Oct 4, 2012

### tiny-tim

Hi Vroc!
It means the velocity Vpa of the plane relative to the air is 100 m/s (N20E)

you're given Vag, the velocity of the air relative to the ground,

and you need to find Vpg, the velocity of the plane relative to the ground.

3. Oct 4, 2012

### Vroc

What? I just need to know what formula to use or how I can use my graph to find the answer.
I'm given the planes Velocity (100m/s n20e) and than the wind (40 m/s s10e)

4. Oct 4, 2012

### tiny-tim

no, that's not the plane's velocity (relative to the ground), it's the plane's velocity relative to the air

5. Oct 4, 2012

### Vroc

Okay, If I can use vector addiction, than I can do it the way I mentioned earlier by making a triangle and finding the unknown side and angle because they both are ways of finding the same thing. correct?

6. Oct 4, 2012

### tiny-tim

correct

(and make sure your vector triangle has the arrows the right way round,

so that Vpg = Vpa + Vag )

7. Oct 4, 2012

### Vroc

Thank you so much.