Four uniform spheres, with masses mA = 37 kg, mB = 30 kg, mC = 220 kg, and mD = 55 kg, have (x, y) coordinates of (0, 50 cm), (0, 0), (-77 cm, 0), and (44 cm, 0), respectively. Find the net force on sphere B due to the other spheres. What are the (a)x and (b)y components of that net force?

I cant figure out what in doing wrong! please help me :)

6 answers

Post your work. I can't figure out what you are doing wrong either.
Im using the F=Gm1m2/r^2.
So to figure out the y i plugged in the values for massA and B and used a radius of .5 to get 2.96E-7.

For the x i used the same formula but did it twice once for particle CB and the other for BD. then i added them together and got -1.74E-7.
ok, you are not considering the forces to be vectors. Adding them as if they are in a straight line won't work. Sketch the locations, and then the forces have to be added as vectors. I would change each force to components in the x and y direction, then add the x's, to get the x sum, and then the same with the Fy.
Here is a similar (simpler) problem. Study it.
http://answers.yahoo.com/question/index?qid=20080331085912AASJv68
Thanks it worked :)
Two insulating spheres have radii 0.300 cm and 0.500 cm, masses 0.500 kg and 0.700 kg, and uniformly distributed charges of -2.00 µC and 3.50 µC. They are released from rest when their centers are separated by 1.00 m.