A force of 90 lb acts on an object at an angle of 55 degrees. A second force of 100 lbs acts on the object at an angle of -60 degrees. Find the direction and magnitude of the resultant force.
First force is not measured in pounds but in newtons so I will pretend the forces are 90 N and 100 N.
Now we can calculate the magnitude of resultant force by using law of cosine (see the image below).
`R=102.4363` <-- Magnitude
Now we can calculate the direction. In order to do that we will first calculate the angle between vector `veca` and resultant vector `vecR` by using law of sine.
`alpha=62^o13'16''` ` `
Now we subtract that from 55° (direction of vector `vecb` ) to get direction of resultant force.
`55^o-62^o13'16''=-7^o13'16''` <-- Direction
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