Engineering Mechanics: Force couple

In summary, the problem is to replace a 150-N force with an equivalent force-couple system at point A. The solution involves converting the force into its components and finding the distance D. The moment is then calculated using the cross product of the force components and distance. It is important to check the direction of the force components to ensure they are correctly oriented.
  • #1
Dfresh
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Homework Statement


Problem is:
Replace the 150-N force with an equivalent force-couple system at A
Since it is really hard to describe the scenario in words, attached is a link that shows the diagram of the question.
http://www.chegg.com/homework-help/questions-and-answers/replace-150-n-force-equivalent-force-couple-system--q3044348

Homework Equations


Cross Product and sum of forces

The Attempt at a Solution


So I have the feeling I screwed up somewhere. What I did was I first converted the force into its components, producing me with -150cos35j+150sin35k. Since one of the things that the question asked was for I just simply took -150cos35 and 150sin35. I then decided to find the D which yields me (-0.1m)i+(0.12m)j+(-0.2m)k. Since the moment is equal to FxD, I took the cross product of these two values to produce me a value of (14.25N m)i+(-8.6N m)j +(-12.29N m)k. I have the strange feeling it is wrong and I screwed up somewhere. Can anyone help me with the problem?
 
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  • #2
Check the direction of the components of the force. Look at the coordinate axes to make sure the components are oriented in the correct sense.
 
  • #3
Ah I see now! Thanks!
 

FAQ: Engineering Mechanics: Force couple

1. What is a force couple in engineering mechanics?

A force couple is a pair of forces that act on an object at different points, causing the object to rotate without any translational motion. The forces are equal in magnitude and opposite in direction, creating a moment or torque that causes the rotation.

2. How is a force couple different from a single force?

In a single force, the line of action passes through the object's center of mass, causing translational motion. In a force couple, the lines of action do not intersect, resulting in rotational motion.

3. What are the applications of force couples in engineering?

Force couples are commonly used in machinery, such as engines, to create rotational motion. They are also used in structural engineering to stabilize buildings and bridges against external forces.

4. How do you calculate the moment of a force couple?

The moment of a force couple is calculated by multiplying one of the forces by the perpendicular distance between the two forces. The direction of the moment is perpendicular to the plane formed by the two forces.

5. Can a force couple produce translational motion?

No, a force couple cannot produce translational motion because the forces are equal and opposite, canceling each other out. However, the resulting moment can cause the object to rotate.

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