- #1
Chubigans
- 21
- 0
Homework Statement
Homework Equations
M = r x F, where r is "a vector directed from the line of action of one of the forces to the line of action of any other force"
The Attempt at a Solution
Well, for the 250 lb couple the r = {3i - 4j - 2k{, F = 250 {3/5i - 4/5j}
M = {-400i - 300j} (I verified this by taking the moments individually)
For F1, r = 3i and F = fyj
so M = 3Fy*k
For F2, r = {-2k} F = {fxi} so M = {-2Fxj}
When we sum the moments, we get {-400i -300 - 2Fxj + 3Fyk }
The x component can never equal zero!
There are two possibilities: I'm misreading the diagram, I'm missing something entirely, or I don't understand the couples idea of getting the vector r between two forces. Please help, I've been doing this for over 5 hours now.