(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Determine resultanat force of vectors P (40N) and Q (60N). P is 20 degrees from reference plane and Q is 45 degrees from reference plane.

2. Relevant equations

When using the parallelogram rule, should you always start with the lowest angle vector? (like in the bottom diagram of the attached image)

3. The attempt at a solution

I solved the question using the parallelogram in two different ways and ended up with different answers. Is there a right way to do this?

Solution 1:

P vector, then Q vector with resultant vector starting at tail of P to tip of Q.

Law of Cosines yields,

R = 97.726N

Law of Sines yields,

Angle A = ∠15.039

alpha = ∠20 + ∠15.039 = ∠35.04

Solution 2:

Q vector, then P vector with resultant vector starting at tail of Q to tip of P.

Law of Cosines yields,

R = 98.542N

Law of Sines yields,

A = ∠7.9803

alpha = ∠45 - ∠7.9803 = ∠37

Diagram attached.

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# Silly Parallelogram Question

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