Basic question - balance of forces....?

In summary, the beam has a force of 100Newtons resting on it at two points, 10 feet apart. The torque about each point is calculated using the force and the distance from the point.
  • #1
tbaker
5
1
I'm trying to find some basic physics information. Suppose you have a (massless) beam, supported at two points, 10 feet apart. You have a force (m*g) of 100 Newtons resting on that beam, say 4 meters from the left point (6 meters from the right)... How much force does that exert on each point, and how do you calculate it...? It seems this would be a simple physics example but I can't seem to find any info on an example like this. I'm working on a trailer hitch problem and the info would be useful...

Thanks.
 
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  • #2
Sorry, I meant the beam is 10 meters long...
 
  • #3
Try looking at the torque about each support, keeping in mind that the net torque about any point must be zero.
 
  • #4
Thanks, but I was looking for a more specific 'example'. I'm not a student trying to get an answer for a homework problem... thanks anyway.
 
  • #5
tbaker said:
Thanks, but I was looking for a more specific 'example'. I'm not a student trying to get an answer for a homework problem... thanks anyway.
That's not how we roll here. For spoon-fed answers you will need to look elsewhere. The expectation is that you will put in some effort, show your work and we will try to help when you get stuck.

So, can you pick a point on the beam and write down expressions for the torque about that point from each of the three forces on the beam?
 
  • #6
So I think I've got it. It's been a while since I've done a physics problem.

So there's a beam (massless), 10 feet long. At each end is a support. A 100 pound weight is 2 feet from the left support (8 feet from the right). The system is in static equilibrium. Call the 100 pound weight F3. The left support F1, the right support F2. So F3 = F1 + F2. Using torque (I'll simplify it as FxD). So, since F1 and F2 are also in equilibrium with each other, F1*D1 = F2*D2, or F1*2 = F2*8.

So, F1 = 4*F2
So, F2 + 4F2 = 100
5F2 = 100
F2 = 20 lbs.
F1 = 80 lbs

Anyhow, I think I have what I need to get an idea what I'm trying to figure out.

Thanks.
 
  • Like
Likes jbriggs444
  • #7
That looks correct.
 
  • #8
Thanks pixel
 

Related to Basic question - balance of forces....?

1. What is meant by the "balance of forces" in basic physics?

The balance of forces refers to the equilibrium state of an object or system where all the forces acting on it cancel each other out, resulting in no net force and therefore no acceleration.

2. How is the balance of forces related to Newton's First Law of Motion?

The balance of forces is directly related to Newton's First Law of Motion, also known as the Law of Inertia. This law states that an object at rest will remain at rest, and an object in motion will continue in a straight line at a constant speed, unless acted upon by an external force. In other words, the balance of forces is what allows objects to maintain their state of motion.

3. What are the different types of forces that can affect the balance of forces?

There are two main types of forces: contact forces and non-contact forces. Contact forces include friction, applied force, normal force, tension, and spring force. Non-contact forces, also known as action-at-a-distance forces, include gravitational force, electrical force, and magnetic force.

4. How can the balance of forces be calculated in a given scenario?

The balance of forces can be calculated using Newton's Second Law of Motion, which states that the net force on an object is equal to its mass times its acceleration. By analyzing all the forces acting on an object and their magnitudes and directions, we can determine whether the object is in equilibrium or if it will accelerate in a certain direction.

5. Can the balance of forces be disrupted or changed?

Yes, the balance of forces can be disrupted by adding or removing forces from an object, or by changing the magnitudes or directions of existing forces. This can result in a change in the object's state of motion, either causing it to accelerate or decelerate. Additionally, external factors such as changing mass or surface conditions can also affect the balance of forces.

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