Understanding Changing Forces in Equilibrium: A Scientific Approach

  • Thread starter UserUnique
  • Start date
  • Tags
    Forces
In summary,-You are asking people to watch a 9 minute video and then you say you are interested in something else. It would be better if you could just make a SIMPLE statement of exactly the scenario you are concerned with (not a scenario you are NOT interested in) and what your issue is.-You are asking people to watch a 9 minute video and then you say you are interested in something else. It would be better if you could just make a SIMPLE statement of exactly the scenario you are concerned with (not a scenario you are NOT interested in) and what your issue is. Also, you have to make SOME effort on your own for us to be able to help you.
  • #1
UserUnique
8
0
Homework Statement
Here in this [video](https://youtu.be/WJQW7sB9G-w) the problem is to find the ratio between the height of water and mercury.(u don't have to watch the whole video. Just look at the drawing so you will have an I idea what I'm talking about)
But I'm interested in something else. Let's say we open the container, and the water pushes the mercury, making it to go up in right side of the v-tube. Let's also change the picture a little bit, and say that the water exits the container at the initial mercury hight, so there is no free fall.
What I want is the ability to measure second by second what is going on, the speed of water exiting the container, what is the maximum hight that the mercury rise to before going back down, the gradual decrease of water force, and gradual increase of mercury resistance force, untill both forces cancel each other.
How do I do that? I have basic high school physics knowledge, like kinematics and Newton dynamics.
But I have no idea how to do what I want there.. for example how to measure mercury maximum hight, and how many seconds will take for it to get there after opening the water container?
I will appreciate assistance in solving this. At least tell me what tools to use?
Relevant Equations
None
Don't know how to approach this problem. I know how to solve 2 opposite constant forces, but in this problem both forces (water and mercury) change with time, until reaching equilibrium.
 
Physics news on Phys.org
  • #2
You are asking people to watch a 9 minute video and then you say you are interested in something else. It would be better if you could just make a SIMPLE statement of exactly the scenario you are concerned with (not a scenario you are NOT interested in) and what your issue is. Also, you have to make SOME effort on your own for us to be able to help you.
 
  • #3
phinds said:
You are asking people to watch a 9 minute video and then you say you are interested in something else. It would be better if you could just make a SIMPLE statement of exactly the scenario you are concerned with (not a scenario you are NOT interested in) and what your issue is. Also, you have to make SOME effort on your own for us to be able to help you.
Ok, sorry. Let me explain it in words. Let's say you have a "v" shaped tube filled with mercury. Now you apply water to the left column of the v-tube. Let's say the initial water height above mercury is H. Let's also say that the water pushes mercury h distance.
So in right v-tube column mercury rises h, while in left column it descends h.
So how do I calculate stuff like the speed of water pushing the mercury, and what is the maximum height that the mercury rises to?
 
  • #4
UserUnique said:
Ok, sorry. Let me explain it in words. Let's say you have a gauge filled with mercury. Now you apply water to the left column of the gauge. Let's say the initial water height above mercury is H. Let's also say that the water pushes mercury h distance.
So in right gauge column mercury rises h, while in left column it descends h.
So how do I calculate stuff like the speed of water pushing the mercury, and what is the maximum height that the mercury rises to?
OK, I THINK I understand what you are asking but it seems incomplete and a bit garbled. First, on the incomplete, you ask how fast the mercury will rise but you do not say how fast the water is inserted. You can't just say it magically appears so you need to say how fast it is inserted. Then on the garbled, you specifically say that the mercury rises a distance h and then ask how high the mercury rises.

Draw a diagram and insert it here with numbers shown EXACTLY what you are talking about and what your question is.
 
  • #5
phinds said:
OK, I THINK I understand what you are asking but it seems incomplete and a bit garbled. First, on the incomplete, you ask how fast the mercury will rise but you do not say how fast the water is inserted. You can't just say it magically appears so you need to say how fast it is inserted. Then on the garbled, you specifically say that the mercury rises a distance h and then ask how high the mercury rises.

Draw a diagram and insert it here with numbers shown EXACTLY what you are talking about and what your question is.
1. Well I did say that the water is at H height. Let's say it's final height will be
(H-h).
2. By "h" I mean mercury's final position. But before that the water will push it higher, until the mercury force will become bigger than water, and stop rising and go back down... until stopping at h (equilibrium).
 
Last edited:
  • #7
phinds said:
DIAGRAM !
Like... You want me to draw?
 
  • #8
Have you thought about applying conservation of energy?
 
  • #9
for the water and mercury, get the density and the volume involved and that should lead to your answers.
 
  • #10
phinds said:
for the water and mercury, get the density and the volume involved and that should lead to your answers.
How will it lead me to answers? Let's say mercury density 10 times higher than water. I don't care about volume. I don't need exact numbers, just an equation. Volume of water enough to push mercury "h" distance down. Whole volume of water is inside left column of the v-tube(previously it was inside container, but let's make it easier and place all water inside the tube with mercury). So naturally it also descends h.
How do I calculate (2)? Max height of mercury?
 
  • #11
jbriggs444 said:
Have you thought about applying conservation of energy?
...can you explain some more pls?
 
  • #12
You start with a configuration with water piled up higher on the left than on the right and a tendency for the left side to sag down and the right side to rise up.

You end with a configuration with mercury piled up higher on the right than on the left. The "sag" has gone past equilibrium. The fluid is rocking back and forth and the right hand side has just reached its first high point.

If we assume that there is negligible energy loss to viscosity, energy is conserved.

Can you calculate the potential energy in the initial configuration? That is, if you labelled the diagram with various heights of the columns, could you write down an expression for that potential energy?

Can you calculate the potential energy in this "final" configuration in the same manner?

Note that this "final" configuration is just the end of the first oscillation to the right, not the ultimate configuration after the oscillations have died out.
 
  • #13
jbriggs444 said:
You start with a configuration with water piled up higher on the left than on the right and a tendency for the left side to sag down and the right side to rise up.

You end with a configuration with mercury piled up higher on the right than on the left. The "sag" has gone past equilibrium. The fluid is rocking back and forth and the right hand side has just reached its first high point.

If we assume that there is negligible energy loss to viscosity, energy is conserved.

Can you calculate the potential energy in the initial configuration? That is, if you labelled the diagram with various heights of the columns, could you write down an expression for that potential energy?

Can you calculate the potential energy in this "final" configuration in the same manner?

Note that this "final" configuration is just the end of the first oscillation to the right, not the ultimate configuration after the oscillations have died out.
Oh... So technically our columns should descend and ascend forever, without damping? (Just like this thing with marbles hitting each other that people put on a desk)?
 
  • #14
UserUnique said:
Oh... So technically our columns should descend and ascend forever, without damping?
Yes, if there were no damping.
 
  • #15
jbriggs444 said:
Yes, if there were no damping.
Ok, that makes sense. Thank you.
 

FAQ: Understanding Changing Forces in Equilibrium: A Scientific Approach

What is the problem with changing forces?

The problem with changing forces is that they can cause unpredictable and often unwanted effects on objects or systems. This can make it difficult to accurately predict the behavior of these objects or systems.

How do forces affect motion?

Forces can either cause an object to start moving, stop moving, or change its direction or speed. The type and magnitude of the force will determine the resulting motion of the object.

How do we measure forces?

Forces are measured using a unit called Newtons (N). This unit is based on the amount of force needed to accelerate a mass of 1 kilogram at a rate of 1 meter per second squared.

Can forces be balanced?

Yes, forces can be balanced when they are equal in magnitude and opposite in direction. This means that the net force acting on an object is zero, resulting in no change in motion.

What is the difference between a contact force and a non-contact force?

A contact force is a force that requires physical contact between two objects, such as pushing or pulling. A non-contact force, also known as an action-at-a-distance force, does not require physical contact and can act over a distance, such as gravitational or magnetic forces.

Similar threads

Understanding the generic nature of linearity in Physics
Replies
2
Views
580
Confused about how forces in a pulley balance
Replies
6
Views
497
Use of imaginary charge vs Gauss' law
Replies
12
Views
396
Moving charge deflected by a loop of wire
Replies
1
Views
355
Friction force on a ball falling through a body of water
Replies
9
Views
581
Proving Newton's 3rd law from conservation of momentum
Replies
2
Views
347
Exploring the Relationship between Buoyancy Force and Gravitational Force
Replies
5
Views
1K
Pearson HW23, The Little Prince
Replies
2
Views
551
Exploring the Equilibrium of a System: Net Force & Net Work
Replies
9
Views
1K
How to find the equilibrium position of three masses (two of them fixed)?
Replies
4
Views
1K

Hot Threads

Recent Insights

Back
Top