# Resultant Force

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• April 25th 2009, 03:34 PM
Tek
Resultant Force
Forces with magnitudes of 85 pounds and 50 pounds act on a single point. The angle between the forces is 15 degrees. Describe the resultant force.

The answer in the book is: "The resultant force is 113.92 pounds and 5.6 degrees from the 85-pound force."

For the life of me I cannot understand how to obtain this answer though...
• April 25th 2009, 04:30 PM
galactus
Is there a diagram to go along with the problem?. That may help.

Try the law of cosines.

$75+\sqrt{85^{2}+50^{2}-2\cdot 85\cdot 50\cdot cos(15)}\approx 113.92$
• April 25th 2009, 04:33 PM
VonNemo19
Now go solve this thing!
Hey Tek, A parrallelogram is formed from the two added force vectors. The law of cosines is all you need to solve this problem.

http://upload.wikimedia.org/math/d/6...22fc14aede.png (you can solve for a to make your life easier)

So let alpha be equal to 165 (365-15-15 because you need that angle to use this formula) and let b and c be be the sides ajacent to the angle and let b=the resultant vector. I'm pretty sure that's all ya need.(Wink)

If youneed more help let me Know!