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.