# Fighter Jet Vector Help

1. Dec 2, 2007

### goodie2shoes

Hello. I do not really understand how to solve these problems and was hoping that you could help/explain them to me. Thanks.

1. A fighter plane moving 200 m/s horizontally fires a projectile with speed 50.0 m/s in a forward direction 30 degrees below the horizontal. What is the speed of the projectile with respect to a stationary observer on the ground?
I was thinking to use cosθ = A/H. But that doesn't work. How do I set up this problem?!

2. Three forces, each having a magnitude of 30N, pull on an object in directions that are 120 degrees apart from each other. What is the resultant?

3. An airplane with a speed of 120km/h is headed 30 degrees east of north in a wind blowing due east at 30km/h. What is the speed of the plane relative to the ground?
I tried using cos, sin/ tan, but somehow I can't get the answer again.

4. Two forces are acting upon an object as shown. What is the magnitude of the resultant forces.?

So basically I kind redid the diagram here. a is 75 degrees between the left hand side lines (slashes) and the box and b is 60 degrees for the right hand side lines (slashes) and the box.

80N....\...../...120N
...........\.../
.........a .\./.....b
........ ----------
........|............|
........
I was going to use F and such to solve for the resultant but no mass is given and I can't think of another way to solve for it.

Thanks for your help. Much appreciated.

Last edited: Dec 2, 2007