Simple, resultant force problem but stuck.

In summary, the conversation discusses finding the height at which the resultant of three forces acts. The solution involves using the moment formula and solving for distance. The final answer is that at 45 inches above the base B, there is 100 pounds of force acting towards the right. The conversation also mentions the use of Verignon's law and taking moments about any point.
  • #1
frozenguy
192
0

Homework Statement


Determine the height h above the base B at which the resultant of the three forces acts.
prob280.jpg


Homework Equations


Rx=F1,x + F2,x + F3,x

The Attempt at a Solution


Rx=(-300)+650+(-250)
Rx=100

but where?! The picture shows the diameter decreasing a tad just under the 650 force, does that matter?

Anyways, am I suppose to use moments/couples? Dont moments/couples have to be equal in magnitude, opposite/parallel?

Thanks,

Frozenguy
 
Last edited:
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  • #2
Hi there, Now I remember only a little bit from my statics class, but you did find fx correctly. Now for the height. Moments are the correct way to do it, I would suggest to find the total for all moments and see where you can go from there. Once you get that, think of the moment formula (M=distance x force). And keep in mind your trying to solve for distance.
 
  • #3
LP20 said:
Hi there, Now I remember only a little bit from my statics class, but you did find fx correctly. Now for the height. Moments are the correct way to do it, I would suggest to find the total for all moments and see where you can go from there. Once you get that, think of the moment formula (M=distance x force). And keep in mind your trying to solve for distance.

Oh ok!

So I add up M1, M2, and M3 (defining base B as the point of rotation) and that will be M0 because of that guys law (I'm terrible, I need to look up his name). Then M0 divided by the magnitude of R will be the distance d.
 
  • #4
It should be. Do you have an answer for it in the book?
I got an answer that seems reasonable. What's yours?
 
  • #5
I got that h would be equal to 45" above base B..

It's an even problem, which the book lacks answers for :/

I think this answer makes sense.. so is it saying that at 45" above B, there is 100lb of force acting towards the right? Or is this just to gauge the relationship between the forces?Thanks so much for your help btw.
 
  • #6
That is exactly what it is saying, your resultant force is 100lb above B 45". This moment equals all the other moments acting on the beam from the other forces. Just like summing up the forces, your summing up the moments.

No problem for the help. I've been helped many times on here before, I figured I'd give back to the community.
 
  • #7
The beauty of this is that you can take moments about ANY point
 
  • #8
what do you mean any point? are you referring to verignons lawl?
 

1. What is a resultant force?

A resultant force is the combined force that results from the combination of two or more individual forces acting on an object. It is the net force that determines the overall motion of the object.

2. How do I calculate the resultant force?

To calculate the resultant force, you need to determine the magnitude and direction of each individual force acting on the object. Then, use vector addition to find the sum of all the forces. The resultant force will be the magnitude and direction of this sum.

3. What is the difference between a balanced and unbalanced force?

A balanced force is when the individual forces acting on an object cancel each other out, resulting in no net force and no change in motion. An unbalanced force, on the other hand, is when the individual forces do not cancel out, resulting in a net force and a change in motion.

4. How does the direction of forces affect the resultant force?

The direction of forces plays a crucial role in determining the resultant force. If the individual forces are acting in the same direction, the resultant force will be larger. If the individual forces are acting in opposite directions, the resultant force will be smaller. The direction of the resultant force will also be affected by the direction of the individual forces.

5. What are some real-world examples of resultant forces?

Some real-world examples of resultant forces include pushing a shopping cart, throwing a ball, and swimming against a current. In each of these scenarios, there are multiple forces acting on the object, and the resultant force will determine the overall motion of the object.

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