# Relative velocity problem. NEED HELP.

1. Sep 11, 2007

### sanghoon

1. The problem statement, all variables and given/known data
A jet airliner moving initially at 300 mph due east enters a region where the wind is blowing at 100 miph in a direction 30° north of east. What is the new velocity of the aircraft relative to the ground?

2. Relevant equations
I don't know any equations for this question.

3. The attempt at a solution
I thought it might be like using the 300 mph... caculate the hypotenus velocity vector using the angle, and add 100 mph... I don't think it's right.

Last edited: Sep 11, 2007
2. Sep 11, 2007

### Staff: Mentor

This is a vector addition problem. One adds the planes velocity vector to the winds velocity vector. The plane is supported/carried by the wind and the wind is moving, which is much like a boat in a river with a current.

So pick a coordinate system, and the determine the components of each vector.

Pick the direction to East as +x, and the direction to North as +y.

3. Sep 11, 2007

### sanghoon

Oh wait... so if the plane's velocity vector was A, and the wind's velocity vector was B.
It would be B + A = R?
R being the new velocity vector relative to the ground.

Last edited: Sep 11, 2007
4. Sep 11, 2007

### Staff: Mentor

Correct!

5. Sep 11, 2007

### sanghoon

Thank you very much. Much easier when you have another to think with.