How do I find the tension and angles in a spider's web?

[madinsane]

Homework Statement

A spider is resting after starting to spin its web. The gravitational force on the spider is 0.165 N on the junction of three strands of silk. The junction is supported by different tension forces in the two strands above it so that the resultant force on the junction is zero. The two sloping strands are perpendicular (the 2 strands above it), and we have chosen the x and y directions to be along them. The tension Tx is 0.112 N.

(a) Find the tension Ty.


N

(b) Find the angle the x-axis makes with the horizontal.


°

(c) Find the angle the y-axis makes with the horizontal.
°

My attempt at this:
For the first one I did
0.165-0.112-x=0
so x=0.053
which was wrong (because I thought the resultant force =0)
I think the second and third depend on the first.
but if I get the first maybe my answer to the second and third may be
cos^-1(y(the first one)/the magnitude)?
I am not sure where to start really, can someone point me in the right direction?

 

[LawrenceC]

If I understand the problem correctly, the spider sits on the vertical leg so it looks like the letter 'y' with the angle of the vee being 90 degrees.

If that is correct set up a force balance at the point where all 3 pieces come together. The vertical forces must sum to the weight of the spider and the horizontal forces must balance.

Looking at the equations, you will have 3 equations with 3 unknowns.

Hint: sin(alpha)=cos(90-alpha), etc

 

[madinsane]

If I understand the problem correctly, the spider sits on the vertical leg so it looks like the letter 'y' with the angle of the vee being 90 degrees.

If that is correct set up a force balance at the point where all 3 pieces come together. The vertical forces must sum to the weight of the spider and the horizontal forces must balance.

Looking at the equations, you will have 3 equations with 3 unknowns.

Hint: sin(alpha)=cos(90-alpha), etc

Thanks for replying...
unfortunately I didn't undersand anything from what you just said,
can you expand?
annd yes the V is 90degrees

 

[LawrenceC]

Do you know what a force balance is? Do I have the geometry correct?

 

[madinsane]

Do you know what a force balance is? Do I have the geometry correct?

No I don't
Would be great if you could explain :D

 

[LawrenceC]

Since nothing is moving in this problem, all forces must balance out. They must sum to zero so sum them in the vertical and horizontal directions. Write equations at the vee that represent this. When you do that you will wind up with three equations and 3 unknowns that you'll have to solve to determine the tension in the other leg of the vee.

 

[madinsane]

Since nothing is moving in this problem, all forces must balance out. They must sum to zero so sum them in the vertical and horizontal directions. Write equations at the vee that represent this. When you do that you will wind up with three equations and 3 unknowns that you'll have to solve to determine the tension in the other leg of the vee.

how do I sum them in the vertical and horizontal direction?

 

[LawrenceC]

You would use trigonometry.

 

[madinsane]

You would use trigonometry.

can you be more specific?

 

[LawrenceC]

You do not sound serious to me. You'll have to find someone else to help.