Determine the resultant couple moment

In summary, the problem involves two couples acting on a beam with a given force of 125 lb. The resultant couple moment can be determined by using the equation M=Fd, where CW is represented by a positive value and CCW is represented by a negative value. The solution for this problem is M=(200*1.5)+(125cos30*1.25). The question of when to use a negative or positive value in the equation can be solved by using the right hand rule, which is not mentioned in the textbook.
  • #1
joker2014
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0

Homework Statement



4-70 Two couples act on the beam. If F=125 lb. determine the resultant couple moment.
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Homework Equations



M=Fd

The Attempt at a Solution


I know CW is + and CCW is - ...and that is determined in the final answer,
I know the solution is taking Forces times the distance, the solution is M=(200*1.5)+(125cos30*1.25)

question is why are they both positive? when do we consider taking negative instead positive? I've seen other solutions for other questions, where they take negative ... I am confused when to take negative or position... so why not -200 or -125 [/B]
 
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  • #2
Are you sure your textbook doesn't explain this? Like mentioning the right hand rule?
 
  • #3
it didnt, otherwise i wouldn't ask here... you could have did me favor and explained rather than asking me a non sense question.. thank you anyways.
 
  • #4
joker2014 said:
it didnt, otherwise i wouldn't ask here... you could have did me favor and explained rather than asking me a non sense question.. thank you anyways.
I dropped a rather big hint.

https://en.wikipedia.org/wiki/Right-hand_rule
 

What is a resultant couple moment?

A resultant couple moment is a measure of the rotational force created by two equal and opposite forces acting on a body at different points. It is represented by a vector and its magnitude is equal to the magnitude of one of the forces multiplied by the perpendicular distance between the forces.

How is the resultant couple moment calculated?

The resultant couple moment can be calculated by multiplying one of the forces by the perpendicular distance between the forces. The direction of the resultant couple moment is determined by the right-hand rule, where the fingers of the right hand curl in the direction of the first force and the thumb points in the direction of the second force.

What is the significance of the resultant couple moment?

The resultant couple moment is significant because it affects the stability and equilibrium of a body. It can cause a body to rotate around its center of mass or cause it to topple over if the moment is larger than the resisting moment of the body.

Can the resultant couple moment be zero?

Yes, the resultant couple moment can be zero if the two forces are parallel or if they have equal magnitudes and are applied at equal distances from the center of mass of the body. In this case, the forces cancel each other out and there is no rotational force.

How is the resultant couple moment different from the resultant force?

The resultant couple moment and the resultant force are different because they act on different aspects of a body. The resultant force causes linear motion while the resultant couple moment causes rotational motion. Additionally, the resultant force is a vector while the resultant couple moment is a vector moment.

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