How Can I Find Force Components at D and C Using Moments?

In summary, the conversation discusses finding the components of the force at points D and C using moments. The force from the 70 kg weight is 686N and the moment about point C is 1715k. The white line in the picture represents the force required to keep the device in equilibrium. The conversation ends with the acknowledgement that the moment about C does not provide enough information to calculate the components of the force.
  • #1
hockeyguy314
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Homework Statement


Find the components of the force at D and C using moments

picture attached



Homework Equations



M=F x r


The Attempt at a Solution



I'm really stuck on this one. The force from the 70 kg weight is 70*9.8 = 686N, so F=-686j. I found the moment about point C to be Mc=1715k. After that, I'm not sure where to go. I'm also really thrown off by the white line that's at a 60° angle below the x axis. Any help would be greatly appreciated. Thanks.
 

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  • #2
It looks to me that the white line is an arrow representing the force required to keep the device in equilibrium. Does that help?
 
  • #3
Yes, it does help thank you. I still don't know where to go from here though. I guess I'm not really sure how the moment about C would translate into components of force.
 
  • #4
Well, do you not know enough to be able to calculate the white force itself, even if you don't know its components?
 
  • #5


As a scientist, it is important to approach problems systematically and logically. In this case, we are dealing with moments, which are a measure of the rotational effect of a force. The equation for moments is M = F x r, where F is the force and r is the distance from the point of rotation.

To find the components of the force at D and C, we can start by drawing a free body diagram of the system. This will help us visualize the forces and their directions.

Next, we can use the moment equation to find the moment at point D, which is the sum of the moments of all forces acting on the system. This can be done by taking the cross product of the force at D (Fd) and its distance from point D (rD).

Similarly, we can find the moment at point C by taking the cross product of the force at C (Fc) and its distance from point C (rC).

Now, we have two equations (Md and Mc) and two unknowns (Fd and Fc) which can be solved using basic algebra.

The white line at a 60° angle below the x-axis is a reference line to help us visualize the forces and their directions. It does not affect the calculations, as long as we are consistent with our coordinate system.

I hope this helps guide you in the right direction. Remember to always approach problems systematically and don't hesitate to seek help when needed.
 

FAQ: How Can I Find Force Components at D and C Using Moments?

What is a moment in statics?

A moment in statics is a measure of the tendency of a force to rotate an object about a specific point or axis. It is calculated by multiplying the magnitude of the force by the distance from the point or axis.

How do you calculate the moment of a force?

The moment of a force can be calculated by multiplying the magnitude of the force by the perpendicular distance from the point or axis of rotation to the line of action of the force. This can be represented by the formula M = F x d.

What is the principle of moments in statics?

The principle of moments states that for an object to be in equilibrium, the sum of the clockwise moments about any point must be equal to the sum of the counterclockwise moments about the same point. This principle is also known as the law of moments or the principle of balance.

What is the difference between a moment and a torque?

In statics, a moment refers to the rotational effect of a force, while torque specifically refers to the rotational effect of a force applied at a distance from a pivot point. In other words, torque is a type of moment that involves a force acting at a distance from the point of rotation.

How do you find the point of application of a force in a moment problem?

To find the point of application of a force in a moment problem, you can use the principle of moments. Set up an equation with the sum of clockwise moments equal to the sum of counterclockwise moments, and then solve for the unknown distance or point. Alternatively, you can use vector analysis and trigonometry to find the position of the force in relation to the point of rotation.

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