Tension in a string at an angle

AI Thread Summary
The discussion revolves around calculating the tension in a wire supporting a 2.15 kg picture at a 15-degree angle from the horizontal. The user initially attempted to solve the problem using the equation ΣF + (-ma) = 2Tsinθ - ma = 0, arriving at a tension of 38.1 N. However, it was pointed out that the correct approach involves using ΣFy = 0 for equilibrium, leading to the equation 2Tsinθ - mg = 0. The user later realized a calculation error due to using 9.18 instead of 9.81 for gravitational acceleration, which affected their result. Overall, the tension calculation is confirmed to be correct, with emphasis on ensuring accurate values in calculations.
BikeSmoth
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Homework Statement


A wire of negligible mass is used to hang a 2.15 kg picture. The ends of the wire are attached to the top 2 corners of the picture. Each end of the wire forms an angle of 15.0 degrees from the horizontal. What is the tension in the wire?



Homework Equations


\SigmaF=ma


The Attempt at a Solution


This is my latest and posiibly best attmept so far, but I don't have anyone to tell me if its right or not.
\SigmaF+(-ma)=2Tsin\theta-ma=0
2Tsin15-19.737=0
T=38.1N
 
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It's correct
 
on which wire would you like the tension for?
 
Yes it looks correct to me.

Though you should put ΣFy=0 when the picture is in equilibrium and then rearrange to get T.

2Tsinθ-mg=0
 
there is only one wire with the picture connected at the two ends hanging down.
 
well it looks like my brilliant self put 9.18 instead of 9.81 in my calculator and subsequently got the question wrong. Man I hate online homework so much!
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
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Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
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