Question

Three forces with magnitude 70 pounds, 40 pounds, and 60 pounds act on objects of -30, 45, and 135 (degrees), respectively, with the positive x-axis. Find the direction and magnitude of the resultant of these forces.

Answer 1

Don't know if it is the easiest or not (less easy to make a mistake) but you could resolve the three forces in the NS and EW directions and finally add the results.
So 60 cos 45 - 40 cos 45 - etc etc

Answer 2

That's what I tried to do, but the answers didn't seem correct. The decimals were either too high, or too low

Answer 3

For instance, if I said:
70cos(-30) + 40cos(45) + 6ocos(135) , the answer wouldn't seem correct

Answer 4

On a quick look (I'm not very good a t calculations) I get
-20sqrt2+35sqrt3 East
100/sqrt2 -35 North

Answer 5

How?

Answer 6

Like I said above, 60 cos 45 (this is 135 in W direction) etc, just resolve each force to the "nearest" of EW or NS directions.

Answer 7

I don't understand. Isn't that what I was doing?

Answer 8

I don't know what you were doing.....

Answer 9

You have to split every force to it's x and y axes forces. Add all the x and y accordingly and then combine the final x and y to create one big force.

You might want to draw out a picture with angles so we can a clear view.

Answer 10

Yes, that's what I said already, it seems the easiest way...

Answer 11

Can you show your work for me? Please

Answer 12

Okay, is that right?

Answer 13

I think I will leave Romero to explain further.

Answer 14

See how force F creates a triangle with a force in the x and a force in the y. Those two forces are the same if we add them together as F. So use cos and sin to split the force F into its x and y. Add all the x and y forces and then that's it.

Answer 15

Okay, so do I have to even have to square them,add those values together, and take the square root to get the final result?

Answer 16

no you use cos and sin to find those values.

Add all the X forces
add all the Y forces.

To get the magnitude you do have to add the squares and then square root the final number. But you have to find the angle and to do this you have to use cos and sin again with the final X force and final Y force you got.

Answer 17

Okay, I understand everything up unto finding the angle.

Answer 18

Ok once you have the final x and the final y you are left with two forces.