Solving Equilibrium Problem: Determine tan θ

In summary, the conversation discusses how to determine the value of tan θ in a system of static equilibrium, using the equations ΣF = 0 and Στ = 0. The individual provides a sketch of a free body diagram and explains the process of choosing a convenient point for the origin to set up Στ = 0. Ultimately, the correct value of tan θ is found to be 3/4.
  • #1
terryds
392
13

Homework Statement



il9g09.jpg


The system is on static equilibrium. Determine tan θ !

Homework Equations


ΣF = 0
Στ = 0

The Attempt at a Solution



∑Fx = 0
Ta sin θ = Tb

ΣFy = 0
Ta cos θ = mg

Then, I got stuck..
I want to continue to Στ = 0 but I don't know which one to pick as fulcrum, the perpendicular forces acting on the block. It's hard to imagine where is actually the θ in the block section.

Please help me..
 
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  • #2
terryds said:

The Attempt at a Solution



∑Fx = 0
Ta sin θ = Tb

ΣFy = 0
Ta cos θ = mg
OK so far.

Then, I got stuck..
I want to continue to Στ = 0 but I don't know which one to pick as fulcrum, the perpendicular forces acting on the block.
For static equilibrium Στ = 0 about any point. So, you can pick any convenient point for setting up Στ = 0.

It's hard to imagine where is actually the θ in the block section.Please help me..
I'm not sure what you mean here.
Be sure to draw a good free body. Pick a convenient point for the origin and set up Στ = 0.
 
  • #3
Okay, this is my sketch of free body diagram
o6fst5.jpg

I pick the bottom of the block as the fulcrum (so Tb is eliminated)

∑τ = 0
W * 15 cm - Ta cos θ * 30 cm = 0

Then, I pick the top of the block as the fulcrum (so Ta is eliminated)
∑τ = 0
W * 15 cm - Tb * 20 cm = 0
Tb = (3/4) W

From
∑Fx = 0
Ta sin θ = Tb

ΣFy = 0
Ta cos θ = W

tan θ = Tb / W = (3/4) W / W = 3/4

Is it correct ?
 
  • #4
Correct. Good. You might try picking the origin (fulcrum) at the upper left end of the rod and see if you get the same answer.
 
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1. How do you determine the value of tan θ in an equilibrium problem?

In order to determine the value of tan θ in an equilibrium problem, you must first identify all the forces acting on the object and their respective magnitudes and directions. Then, using the principles of equilibrium, you can set up a system of equations to solve for the unknown values, including tan θ.

2. What is the significance of determining tan θ in an equilibrium problem?

Tan θ represents the ratio of the perpendicular component of a force to the parallel component of the force. In an equilibrium problem, determining tan θ can help you understand the balance of forces acting on an object and whether or not it will remain in equilibrium.

3. Can tan θ ever be negative in an equilibrium problem?

No, tan θ cannot be negative in an equilibrium problem. This is because the tangent function is defined as the ratio of two sides of a right triangle, and therefore cannot have a negative value. In cases where the value of tan θ appears to be negative, it actually represents a force acting in the opposite direction.

4. What are some common mistakes when solving for tan θ in an equilibrium problem?

One common mistake is incorrectly identifying the direction of forces, which can lead to incorrect values for tan θ. It is also important to remember to include all forces acting on the object, including any forces of friction or tension. Lastly, not properly setting up and solving the equations can also lead to mistakes when determining tan θ.

5. Are there any shortcuts or tricks when solving for tan θ in an equilibrium problem?

While there are no shortcuts, it can be helpful to draw a clear and accurate diagram with all the forces labeled and their directions indicated. This can help you visualize the problem and make it easier to set up and solve the equations. It is also important to double check your work and make sure all values and directions are correct before determining tan θ.

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