How do I solve a tension and torque problem without prior knowledge?

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    Tension Torque
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Homework Help Overview

The discussion revolves around a tension and torque problem, with the original poster expressing uncertainty about how to approach it due to a lack of prior knowledge on the topic. The subject area includes concepts related to forces, free body diagrams, and torque calculations.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants suggest starting with a free body diagram to visualize the forces acting on the object. There is a focus on identifying the forces involved, including tension from strings and gravitational force. Questions about the original poster's prior knowledge of free body diagrams and center of mass are raised.

Discussion Status

Some participants have offered guidance on how to begin the problem, emphasizing the importance of drawing a free body diagram and considering torque equations. There is an ongoing exploration of how to approach the problem without prior knowledge, with no explicit consensus reached yet.

Contextual Notes

The original poster indicates a lack of exposure to the relevant concepts in their lectures, which may affect their understanding of the problem. Participants remind the original poster of the forum's guidelines regarding effort and engagement in the learning process.

marinarasauce
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Homework Statement
An 87 cm long metal bar has a mass of .695 kg and is supported by 2 strings

-Find the tension in each string

-Find the center of the mass for the bar relative to the left end of the bar
Relevant Equations
I think we use
Torque= F r sin theta....?
I have no idea where to start or how to do this. I haven't learned this in lecture yet
 

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Welcome to PF.

marinarasauce said:
I have no idea where to start or how to do this.
With problems like this it's best to start with a Free Body Diagram (FBD) of the object that shows all of the forces acting on it (in this case the two strings pulling up at their contact points with the angles, along with the force of gravity acting down on the bar at it's center of gravity point). Once you have your FBD drawn and labeled, you write the equations to sum all of the forces to zero and to sum all of the torques to zero.

Try sketching that FBD for us and upload it using the "Attach files" link below the Edit window.

EDIT -- Beat out by @kuruman again! :smile:
 
To elaborate on @berkeman 's reply, you need to pick an axis for the torque equation. Generally one chooses a point at which some of the forces act so that those do not feature in the equation. Occasionally it pays to pick two axes and write the torque equation for each, but for a single free body that is usually redundant since it can be deduced from the other torque equation and the linear equations.
 

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