Equilibrium Force Question Homework

[joedozzi]

Homework Statement

a.
A bag of cement of weight 290 N hangs from three wires as shown in the figure below.


[PLAIN]http://capa.physics.mcmaster.ca/figures/sb/Graph05/sb-pic0524.png

Two of the wires make angles θ1 = 57.1° and θ2 = 25.0° with the horizontal. If the system is in equilibrium, calculate the tension T1.

b.
Calculate the tension T2.


c.
Calculate the tension T3.

Homework Equations

Anything to with kinematics/force

The Attempt at a Solution

no idea...

 

[DR13]

Think about the relationship between the forces on the hanging mass and the tension in T3. What is the net force on the hanging mass? What forces attribute to this net force? Then try to find a relation between T3 and T2 and T1. What component of T2 and T1 do you need? How is this related to theta?

 

[joedozzi]

UPDATE:

How do I isolate for T1?

Weight = T1sin(theta1) + [T1cos(theta1)]/[cos(theta2)]xsin(theta2)

 

[DR13]

UPDATE:

How do I isolate for T1?

Weight = T1sin(theta1) + [T1cos(theta1)]/[cos(theta2)]xsin(theta2)

You are making this much too hard. I will give you a big hint. Weight = T1. Now I ask you what the vert compontets of T2 and T3 will have to add up to?

 

[joedozzi]

it should add up to 290N

 

[DR13]

Yup! Can you tell me why this is?

 

[joedozzi]

Okay I get that but I am not sure what to do next. You are saying that my T1 is 290N? I did figure out my T3 is 290N? How do I figure out T2?

 

[DR13]

Okay I get that but I am not sure what to do next. You are saying that my T1 is 290N? I did figure out my T3 is 290N? How do I figure out T2?

Wow I am sorry I made a typo. T3 will equal weight and the vert components of T3 and T2 will sum to weight. Now try it.

 

[joedozzi]

So i understand, that T3=290N but How do I vert components T1 and T2?
Using sin?

 

[DR13]

So i understand, that T3=290N but How do I vert components T1 and T2?
Using sin?

Yup use sine.

 

[joedozzi]

So sin57.1 + sin25.0 = 290N
this would give me T1 and T2?

 

[DR13]

So sin57.1 + sin25.0 = 290N
this would give me T1 and T2?

Well not quite. You don't have T1 and T2 involved in your answer.
T1sin57.1 + T2sin25 = 290

 

[joedozzi]

how do I solve for this if I have two unknowns?

 

[DR13]

Think of it as a proportion. What percent of the force will have to go to T1 as opposed to T2 based on the angles.

This is all I can say for tonight. I have to go now.
Good Luck!