Solve Beam Torque Problem: Find Cord Tension & Hinge Force

  • Thread starter Mr. Snookums
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In summary: So yes, you you can take moments about the hinge and solve for the y-component of the hinge force.In summary, there is an 80kg beam attached to a hinge on a wall and supported by a cord. The angle between the cord and the beam is 25 degrees, and the length of the beam is 4.5m. There is also a 20kg beam hanging from the very tip of the beam. By balancing the torques, the tension in the cord is found to be 1790N. To find the force exerted by the hinge, the x-component (1790 cos(25)) and y-component (1790 sin(25)) of the reaction force are calculated. Taking moments about the
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Mr. Snookums
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There is an 80kg beam attached to a hinge on a wall and supported by a cord. The angle between the cord and the beam is 25 degrees. The beam is 4.5m long., and the cord is attached to the beam a metre from the beam's end. There is a 20kg beam hanging from the very tip of the beam. Find the cord tension and the force exerted by the hinge.

CW Torque=(80kg)(9.8m/s^2)(2.25m)+(20kg)(9.8m/s^2)(4.50m)
=2646Nm

Since the torques must balance:

2646Nm=F(3.5m)
F=756N

Plug this into the right triangle created by the cord and the beam:

Tension in the cord=cos65/756N=1790N

Now here's where I have the trouble. How do I get the force exerted by the hinge? I found the x xomponent, which is 1790sin65. But when I use this answer to find the force vector of the hinge, I don't get the right answer.

(1790sin65)(sin25)=687N. The answer is 1600N. Where have I gone wrong?
 
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  • #2
The hinge will exert an x and y component force.

You're right that the x-component will be 1790 cos(25) [or as you put it, sin(65)].

Now you have to find the y-component.
 
  • #3
The y-component is the force from the hinge that would balance all the other forces along the beam? Because the torque is already balanced.
 
  • #4
Don't think of it as "balancing" torques. Think of it as setting all of the torques set to 0.

You're right in that if you set all of the vertical forces set to 0 then you can find the y-component of the reaction force at the hinge. The thing to realize though is that if you take the moments (torques) about any point on the beam, they should add to zero. (Well actually if you take the moments about any point in space they should add to zero.)
 
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FAQ: Solve Beam Torque Problem: Find Cord Tension & Hinge Force

What is a beam torque problem?

A beam torque problem is a physics problem that involves finding the tension in a cord and the force at a hinge in a beam structure. This is typically done by analyzing the forces acting on the beam, including the applied load and any external supports or forces.

How do you solve a beam torque problem?

To solve a beam torque problem, you will need to use principles of static equilibrium, which state that the sum of all forces and torques acting on a stationary object must be equal to zero. This means that you will need to set up and solve equations using the known forces and torques to find the unknown tension and hinge force.

What information do I need to solve a beam torque problem?

To solve a beam torque problem, you will need to know the applied load, the length of the beam, the distances between the applied load and the supports, and any other external forces or supports acting on the beam. You may also need to know the material properties of the beam, such as its elasticity and weight.

What are some common mistakes when solving a beam torque problem?

One common mistake when solving a beam torque problem is forgetting to include all of the forces and torques acting on the beam. It is important to carefully consider all external forces and supports to ensure that the equations are set up correctly. Another mistake is using incorrect units or not converting units properly, which can lead to incorrect solutions.

Can computer software be used to solve beam torque problems?

Yes, there are many computer programs and apps that can help solve beam torque problems. These programs use mathematical algorithms and equations to quickly and accurately solve for the tension and hinge force in a beam structure. However, it is still important to have a solid understanding of the principles and equations involved in solving these problems in order to use the software effectively.

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