Posted by anne on .
An object acted on by three forces moves with constant velocity. One force acting on the object is in the positive x direction and has a magnitude of 6.5 N; a second force has a magnitude of 3.9 N and points in the negative y direction. Find the direction and magnitude of the third force acting on the object.

college physics 
K,
Newton's second law states that for every action there is an equal and opposite reaction. Draw a force diagram. It is moving at a constant velocity. Your force diagram for an object moving at a constant velocity is the same as your force diagram for an object at rest, so you can solve the same way. Negative y fOrce of gravity always exists, so the force you are looking for is keeping it up.
I'm not goig to just give you the answer. (ps, I'm a freshman in my 5th week of highschool and I'm in physics, but since we just learned what you're learning, I thought I'd help you. 
college physics 
yo,
that did not help at all

college physics 
Henry,
F1+F2+F3 = M*a = M*0 = 0.
6.5  3.9i + F3 = 0.
F3 = 6.5 + 3.9i = 7.58 N.[31o] N. of W.
= 149o CCW from +xaxis.