Calc Question:

Force 1 = 70 lbs
Force 2 = 100 lbs
Resultant = 80 lbs

What is the angle between the forces given the resultant force is the magnitude.

Question

Calc Question:

Force 1 = 70 lbs
Force 2 = 100 lbs
Resultant = 80 lbs

What is the angle between the forces given the resultant force is the magnitude.

anonymous · Answer

dot product
80 = 70*100*cos(theta)
cos(theta) = 8/700
theta is around 89.35 degrees

anonymous · Answer

I have seen similar problems worked this way, but the book yields the answer as 53 degrees. Any thoughts?

anonymous · Answer

70^2 + 100^2 + 2(70)(100)cos(theta) = 80^2
14000cos(theta) = -8500
cos(theta) = -17/28
theta = 127.383
adjust for negative
53

anonymous · Answer

^-- law of cosine

anonymous · Answer

sorry for mistake :x

anonymous · Answer

Excuse my unintelligent moment...but may I inquire on how you got the -8500.

anonymous · Answer

80^2 - 70^2 - 100^2 = -8500
i moved all numbers to right side

anonymous · Answer

AH! Alright. Thanks for the help
*Medal Given*

anonymous · Answer

lol thanks and no problem