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Dogs pulling on a post vector probelmby kirby27
Tags: vector analysis 
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#1
Oct611, 06:49 PM

P: 32

Two dogs pull horizontally on ropes attached to a post; the angle between the ropes is 60.5.
If dog A exerts a force of 250 and dog B exerts a force of 330 , find the magnitude of the resultant force. Find the the angle the resultant force makes with dog A's rope. I dont know where to start because i dont know what to do with the 60.5 degrees. should i split it equally between the dogs (30.25 each)? does it matter? or am i doing it wrong? 


#2
Oct611, 07:12 PM

PF Gold
P: 1,053




#3
Oct611, 07:40 PM

P: 32

ok. i know not to split the angle, but now i dont know how to get started.



#4
Oct611, 07:49 PM

PF Gold
P: 1,053

Dogs pulling on a post vector probelm
You realize that this is a vector addition question, yes? What methods have you used in the past? There is the graphical method with rulers and protractors, the parallelogram method if you like trig functions, to start.



#5
Oct611, 09:01 PM

P: 32

i'm very good at vector adition, but i dont know how to divide these two vectors into their components. if i had angles for each vector i would understand how to do the problem



#6
Oct611, 09:11 PM

PF Gold
P: 1,053

Well then pick one of the dog vectors so that it aligns with the +x axis. Put the other dog vector at the angle 60.5° CW (or CCWit does not matter) from the first dog and then add them using the component method.



#7
Oct611, 09:30 PM

P: 32

ok but the question says that the dogs pull "horizontally." This means that they are both pulling on the xaxis, and their angle is created in the yaxis. isn't the wording unclear?



#8
Oct611, 09:35 PM

PF Gold
P: 1,053

I did not read it that way. "pulling horizontally" means that all their force is applied in a horizontal plane.



#9
Oct611, 09:42 PM

P: 32

im gonna trust you on this one



#10
Oct611, 09:43 PM

PF Gold
P: 1,053

So, to be clear, this horizontal plane consists of an xaxis (+x pointing east, say) and a yaxis (+y pointing north). The dogs pulling horizontally means there is no zcomponent of force. [Edit: No short dog, tall dog scenario. ]



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