Posted by **Hannah** on Wednesday, March 31, 2010 at 9:37pm.

Three forces with magnitudes of 70 pounds, 40 pounds, and 60 pounds act on an object at angles of -30 degrees, 45 degrees, and 135 degrees, respectively, with the positive x-axis. Find the direction and manitude of the resultant of these forces.

Please explain. I really do not understand these.

- Math -
**Reiny**, Wednesday, March 31, 2010 at 10:05pm
The three vectors can be written as

(70cos(-30),70sin(-30)) or (60.622, -35)

(40cos45,40sin45), or (28.2843, 28.2843)

(60cos135,60sin135) or -42.4264, 42.4264)

so the sum of those three vectors is

(46.4799, 35.7107)

the magnitude of that is

√(46.4799^2 + 35.7107^2) = 58.614

the direction would be arctan(35.7107/46.4799) = 37.535°

- Math -
**Hannah**, Wednesday, March 31, 2010 at 10:45pm
Thank You!

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