Author Topic: Physics question about a yachts mast  (Read 399 times)

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Offline Skiffy Wolf

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Physics question about a yachts mast
« on: November 04, 2014, 02:18:14 am »
So I have this one question for physics in this past exam and the answers don't seem to have the answers for this part of the exam and I am unable to figure it out. The question is:

The vertical mast of the yacht below is held up by steel cables attached to the hull. The tip of the mast, A, is at equilibrium


(A) On the above diagram, show the direction of the total force on A from the two cables.
(B) Explain your reasoning for your answer in (A).
(C) Calculate the force on A from cable (2).

Please help I am actually super lost on this question. All I know is that all the forces will be equal since it is an equilibrium. I don't know what to do after that.
« Last Edit: November 04, 2014, 02:30:26 am by Skiffy Wolf Skiffington »

Offline Jethro

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Re: Physics question about a yachts mast
« Reply #1 on: November 04, 2014, 03:12:18 am »
I can probably help you if I remember tomorrow. I'm currently not in a good state of mind for this.

Breaking the force into components is usually best.  So split your cable 1 up.  500N * sin(40) to get your X component and 500N * cos(40) to get your Y.
*Remember, I switched cos and sin because you're taking the angle from the vertical!

Then your cable 2 is   T*sin(30) for X and T*cos(30) for Y.   

Now you can set 500N*sin(40) - T*sin(30)=0 to solve for T .   Or 500N*cos(40) + T*cos(30) = 0       I /believe/ these two will give you the same answer for what T is.

Then once you have T; you add the x and y components from both:  X is  500N*sin(40) - T*sin(30) because you now know T  and then Y is 500N*cos(40) + T*cos(30)
 and then do Sqrt(x^2 + y^2) to get the magnitude- the resultant force A.
You can also do the inverse of tangent, tan^-1 (y/x) to get your angle.

I really hope this helps.
« Last Edit: November 08, 2014, 10:03:56 pm by Panda♡♡ »

Offline Skiffy Wolf

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Re: Physics question about a yachts mast
« Reply #2 on: November 06, 2014, 11:29:07 pm »
Thank you. I followed what you said and got an answer of 848.62 for force A. Not sure if it's correct seeing as I may have made a mistake somewhere (as I nearly did until I noticed it). Thanks again.