Calculating tensions in ropes suspending an onject

novae
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Homework Statement


A mass of 20 kg is suspended from a ceiling by two lengths of rope that make angles of 30° and 45° with the ceiling . Determine the tension in each of the strings.

2.Relevant equations

Fg= mg

The Attempt at a Solution


Fg= 20 x 9.8 = 196 N

∑F= fnet=ma
Fg-FTtotal= 0
196= FTtotal
196= FT1y+ FT2y (y components of each of the tensions)
196= (cos60)(FT1) + (cos45)(FT2)
I think I'm doing something wrong and I don't knownwhat. In the textbook, instead of using the y components of the tensions, they just use the tensions, which doesn't make sense to me because it's the y components of the tensions that give the equilibrant force to Fg.
 
What you're doing is fine, but don't forget the x-components. That will give you the second equation that you need to solve for your two unknowns.
 
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Doc Al said:
What you're doing is fine, but don't forget the x-components. That will give you the second equation that you need to solve for your two unknowns.
Ohhhhh right! I forgot about that! And then it's substitution and stuff from there, thank you!
 

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