Statics Question: Finding Resultant Moment

In summary, the magnitude and direction of the resultant moment produced by the forces about point O are determined by breaking the forces down into their components and calculating their individual moments. The sum of these moments is -268.33 Nm, indicating a clockwise rotation. The x components do not affect the direction of rotation.
  • #1
Chandasouk
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http://img831.imageshack.us/img831/8005/f48am.jpg [Broken]

Determine the magnitude of the resultant moment produced by the forces about point O

Determine the direction of the resultant moment produced by the forces about point O

I first break the forces down to their components.

F1x = 500(4/5)

F1y=500(3/5)

F2x=600cos(60)

F2y=600sin(60)

The problem for me is when it comes time to add their moments. I am taking counter clockwise to be POSITIVE and clockwise to be NEGATIVE.

MF1x= -500(4/5)(0.25) = -100

MF1y= 500(3/5)(0.425) = 127.5

MF2x= -600cos(60) (0.25)=-75

MF2y= -600sin(60)(0.425) = -220.836478

so ƩM = -268.33 Nm turning clockwise?

The directions of the X components are confusing me, I would imagine they would cause the object to turn clockwise? I have only a few tries left on my HW so I just wanted to be sure of my answer.
 
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  • #2
Your work looks good to me. (I don't see why you find the x components confusing.)
 

1. How do you calculate the resultant moment?

To calculate the resultant moment, you need to find the sum of all the individual moments acting on an object. This can be done by multiplying the force by the distance from the point of rotation to the line of action of the force. The resultant moment is a vector quantity, so it also has direction and can be represented by a moment vector.

2. What is the difference between a moment and a force?

A moment is a rotational force that causes an object to rotate about a fixed point, while a force is a push or pull that causes an object to move in a straight line. Moments are measured in units of force multiplied by distance, while forces are measured in units of mass multiplied by acceleration.

3. How do you find the direction of the resultant moment?

The direction of the resultant moment can be found using the right-hand rule. Point your thumb in the direction of the force and curl your fingers in the direction of rotation. The direction of your fingers will indicate the direction of the resultant moment.

4. What is the principle of moments?

The principle of moments states that for an object to be in equilibrium, the sum of the clockwise moments must be equal to the sum of the counterclockwise moments about any point. This means that the object will not rotate as long as the moments are balanced.

5. How do you find the resultant moment in a system of forces?

To find the resultant moment in a system of forces, you must first find the sum of all the individual moments using the principle of moments. Then, you can use the Pythagorean theorem to find the magnitude of the resultant moment, and the right-hand rule to determine its direction.

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