A Mass Hanging From Multiple Strings

AI Thread Summary
A 6 kg mass is hanging from string 3, which is connected to two other strings: string 1 to a wall and string 2 to the ceiling at a 40-degree angle. The problem requires calculating the tension in string 2. The user initially calculated the forces using vector equations but encountered an error in their calculations, particularly with the sign of the gravitational force. After receiving feedback, they acknowledged a mistake and plan to discuss the issue with their teacher. The discussion highlights the importance of correctly applying trigonometric functions in physics problems.
Null42
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A mass of 6 kg is hanging from a string, named string 3. The top of this string is connected to to other strings, string one which goes straight to the left to connect with a wall, and string two which connects to the ceiling making a 40 degree angle between the ceiling and the string. The problem is asking for the tension of string 2.
The available answers are:

EDIT: Will try and provide a picture when possible.

a) 1.2 N
b) 11 N
c) 34 N
d) 3.5 N
e) 40 N


I thought I could solve the problem by considering each string a vector, representing the force of each. Since there is no movement, the sum of the Forces should equal 0.
So , T1+T2+T3=0

I figure the force of T3 to be the F_g, which should be 6 *9.8=58.8 N

Using this I then came up with the following
T1*cos(180)+T2*cos(40)+58.8*cos(270) = 0
and
T1*sin(180)+T2*sin(40)+58.8*sin(270)=0

I figured I could use the second equation most easily, since the sin(180)=0.

So, I came up with 0+(.643)T2+58.8=0
(.643)*T2=-58.8
T2=-91.44
Of course, this is nowhere close to any of the available answers, and I can't seem to wrap my head around any other way of doing it. Any help would be greatly appreciated.
 
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Null42 said:
T1*sin(180)+T2*sin(40)+58.8*sin(270)=0

I figured I could use the second equation most easily, since the sin(180)=0.

So, I came up with 0+(.643)T2+58.8=0
(.643)*T2=-58.8
T2=-91.44
Assuming your description is accurate, the available answers are way off.

Your method is perfectly fine. You did make a sign error, but otherwise your answer is correct. (What is sin(270)?)
 
Ahhh, yes, sorry, 58.8 * -1. Thank you for that. I guess I'll just have to discuss it with the teacher. Thanks!
 
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