Statics Question / Understanding Direction

In summary, when determining the sign of a given couple, the Right Hand Rule (RHR) can be used. In this case, the 30 lb couple on the zy-plane has a negative value for its moment, which means it creates a clockwise moment in the z-y plane. To use the RHR, the thumb should be perpendicular to the z-y plane in order to keep the same sign of the moment.
  • #1
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Homework Statement



I'm trying to understand how to determine the sign (+/-) of a given couple. In the sample problem below it shows the 30 lb couple (on the zy-plane) having a negative value for it's force. Is this found by using the RHR? And if so, in which direction do I orient my hand? In the positive direction of the axis it's parallel to?

C3kmH.jpg


Homework Equations



[itex]M = Fd[/itex]

Right Hand Rule

The Attempt at a Solution



I tried to depict the two orientations inside of the picture above.

Thank you for any help / feedback is appreciated.
 
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  • #2
I think you meant to say that it has a negative value for its moment? If you look at the couple you'll see that it causes a clockwise moment in the z-y plane which means it causes a negative moment in the z-y plane. This means that your thumb should be perpendicular to the z-y plane in order for the RHR to be obeyed and keep the same sign of the moment created.
 

FAQ: Statics Question / Understanding Direction

What is "statics" and how does it relate to direction?

Statics is the branch of mechanics that deals with the study of objects at rest or in uniform motion. It is concerned with the analysis of forces and moments acting on a body, and how they affect its equilibrium. The concept of direction is important in statics as it helps to determine the net force and moment acting on an object, which ultimately determines its state of equilibrium.

How do you determine the direction of a force in statics?

The direction of a force in statics is determined by using vector analysis. This involves breaking down the force into its components in the x, y, and z directions. The direction of the force can then be determined based on the signs of these components and their relative magnitudes.

What is the difference between scalar and vector quantities in statics?

In statics, scalar quantities only have magnitude, such as mass or temperature, while vector quantities have both magnitude and direction, such as force or velocity. In order to accurately analyze forces and moments in statics, it is important to differentiate between scalar and vector quantities.

Why is it important to understand direction in statics?

Understanding direction in statics is crucial for accurately determining the equilibrium of an object. Forces and moments have specific directions and magnitudes, and if these are not properly accounted for, the object may not be in equilibrium and could potentially experience undesired motion or failure.

Can objects be in equilibrium if the forces acting on them are not in the same direction?

Yes, objects can still be in equilibrium if the forces acting on them are not in the same direction. However, in order for this to occur, the forces must be balanced and have the same net moment about any point. This means that the sum of the forces in each direction must equal zero, and the sum of the moments about any point must also equal zero. This concept is known as the conditions of equilibrium in statics.

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