Relative Motion Homework Problem?

[rasofia77]

Homework Statement

"To illustrate this principle, consider a plane flying amidst a tailwind. A tailwind is merely a wind that approaches the plane from behind, thus increasing its resulting velocity. If the plane is traveling at a velocity of 100 km/hr with respect to the air, and if the wind velocity is 25 km/hr, then what is the velocity of the plane relative to an observer on the ground below? The resultant velocity of the plane (that is, the result of the wind velocity contributing to the velocity due to the plane's motor) is the vector sum of the velocity of the plane and the velocity of the wind. This resultant velocity is quite easily determined if the wind approaches the plane directly from behind. As shown in the diagram below, the plane travels with a resulting velocity of 125 km/hr relative to the ground."

Homework Equations

oVe =oVm+ mVe (object,medium,earth)

The Attempt at a Solution

I know, it gives the answer- it's from a website (I'm trying to understand relative motion). Okay, now how would I put all of that in the equation below? All I could come up with is planeVair=100, windVair=25, what is planeVground...but I can't put those three into one equation because the objects/mediums aren't the same. So how would I?

[Mod note: Template headers added]

 

[NascentOxygen]

You write windVair. Should be windVground.

For consistency, planeVair should be planeVwind.