# Engineering/Physics

posted by
**Aaron** on
.

A force F = 7^i + 6^j - 5^k lb. acts at the origin. Find the magnitude and

direction cosines of the moment of this force about point A (-4; 5; 6) ft

So in this case wouldn't

vector r= -4i +5j +6k

and

vector F = 7i + 6j - 5k lb?

and r X F = -61i +22j -59k = MA

[MA]= 87.67 ft-lbs

cosα = -61/87.67 => α=134°

cosß= 22/87.67 => ß=75.5°

cosγ= -59/87.67 => γ=132.3°

Not sure exactly where I went wrong because those angles don't make any sense.