Four masses are positioned at the corners of a rectangle, as indicated in the figure below (not to scale).

http://www.webassign.net/walker/12-22alt.gif

1kg ---x--- 2kg
|
y
|
3kg ---x--- 4kg

(a) Find the magnitude and direction of the net force acting on the 2.0 kg mass if x = 0.20 m and y = 0.11 m.

ANSWER: ? N
ANSWER: ? degrees counterclockwise from the x-axis, which points to the right.

(b) How do your answers to part (a) change (if at all) if all sides of the rectangle are doubled in length?

ANSWER: the magnitude should be quadrupled while the direction should remain unchanged.


I have tried finding the magnitude of the force acting on the 2kg mass by finding the sum of all of the gravitational forces acting on it from the three other masses. I am not quite sure how to find the direction but I assume that once I find the components of the force in the x- and y-directions that I would use sine or cosine to find the angle. I have been unable to get either of these answers correct, can anybody help me?

Note: This is based on Chapter 12 Problem 12 from Physics (4th ed.) by James Walker
Steve, thanks so much for your help but the system still says that I am wrong, but within 10% of the correct value.