# Vertical spring connected between two bodies with a rope above them

• physics1000
In summary,At the point where the rope is cut, the masses of M1 and M2 are in equilibrium, with no net force acting on either.
physics1000
Homework Statement
Yes, homework
Relevant Equations
There is no equation in here
Question:
A string spring is connected between two bodys with a rope above them.
M1 = 25Kg
M2 = 50KG
Distance between them is 100m.
I answered a bit and got to the point where the distance between the two masses are 110m ( the mass below got 10m lower and is on balance, I mean, acceleration = 0.
Anyway, in that point, The question is:
The rope has been cut, what is the acceleration?

I couldn't really understand what I should say...
I thought of that:
M1 ( the above mass ) has m1g + Fk below
M2 ( the below mass ) has only m2g.

Am I right in doing this? the reason Fk is not in M2 because the string doesn't do a thing to him, but to M1 it does, because it is heavier.
Am I right?

[Mentor Note -- some corrections applied to this post]

Last edited by a moderator:
Is the rest of the problem on a different forum ?

hmmm27 said:
Is the rest of the problem on a different forum ?
Nope, its the last sub-question on the question. ( There is A,B,C):
A - is something else, not related.
B- Is what I said regarding the distance from 100 to 110.
C - is the cut rope

hmmm27 said:
What is the problem exactly? I don't have a painting? well,, you can understand its a little problematic to paint here right? I can paint:

This is how the question looks like.
Just what it means when i cut the rope.. that's my sole question.
If what i said above is true?

thats the question

Welcome to PF.

Also, what is the rope? Is it holding the masses at some separation before it is cut?

physics1000
berkeman said:
Welcome to PF.

Also, what is the rope? Is it holding the masses at some separation before it is cut?
Sorry, meant spring, I don't know why I wrote string... sorry, my bad.
Regarding the rope:
It is holding the masses.
According to my question:
M1 is 25KG.
M2 is 50KG
I had to find the point where M2 is in balance, It means Acceleration=0. I found it, it is 10 meter below the starting point.
Then for the question of this thread:
What happens if, from that point of the 10meter below the starting point, the rope is being cut?
What I thought is:
M2 has force of m2G below only.
M1 has force of m1G and Fk below.

Reasons for my thoughts:
M2 is heavier then m1, thus, the spring is not doing a thing to him.
in the other hand, M1 is lighter, thus, he will be carried more faster to M2, that's why he has Fk below, means, M1G+Fk is the force below.

Is it true?
Or my other thought ( but less logical ):
M2 has M2G below and FK above, of 10meter ( I thought maybe it returns to his base- starting point ).
M1 has M2G below and Fk below also ( goes 10m down ).

But this thought is less logical then the first, the first one sounds more true to me, but I want to be sure.

physics1000 said:
M2 is heavier then m1, thus, the spring is not doing a thing to him.
If the spring has no mass then there cannot be a net force on it. What does that tell you about the forces the spring exerts on the two masses?
physics1000 said:
What happens if, from that point of the 10meter below the starting point, the rope is being cut?
That's a bit vague. Do you just want the instantaneous acceleration of each mass, or of just one mass, or how the whole system moves thereafter?
physics1000 said:
M2 has M2G below and FK above
And what is the value of Fk at the instant the rope is cut?
physics1000 said:
M1 has M2G below and Fk below
M1 doesn’t 'know' anything about M2. All it experiences are its own weight, the force from the spring, and, until it is cut, the force from the rope.

haruspex said:
If the spring has no mass then there cannot be a net force on it. What does that tell you about the forces the spring exerts on the two masses?

That's a bit vague. Do you just want the instantaneous acceleration of each mass, or of just one mass, or how the whole system moves thereafter?

And what is the value of Fk at the instant the rope is cut?

M1 doesn’t 'know' anything about M2. All it experiences are its own weight, the force from the spring, and, until it is cut, the force from the rope.
Ahh, I see.
I will try to make a solution
Is it Possible I will write in my notebook and send a picture here? because I don't know how to write it all ( plus paintings ) in forum.

physics1000 said:
Ahh, I see.
I will try to make a solution
Is it Possible I will write in my notebook and send a picture here? because I don't know how to write it all ( plus paintings ) in forum.
Images are for diagrams and textbook extracts. Please take the trouble to type in your working.
Latex is preferred (click LaTeX Guide below the text entry panel), but not essential.

haruspex said:
Images are for diagrams and textbook extracts. Please take the trouble to type in your working.
Latex is preferred (click LaTeX Guide below the text entry panel), but not essential.
Problem is, there isn't any much writing in this question, its mostly the painting itself.
But okay, I will try, I will send a picture of the painting and write what I did here.

berkeman
EDIT:
Here was a picture of my last solution before the actual one.
It was wrong, don't mind it.

Last edited:
You can close post, I got good with this question...
Thanks anyway ( although I didnt get any answers ).

physics1000 said:
You can close post, I got good with this question...
Thanks anyway ( although I didnt get any answers ).
What answer did you get? It bothers me that your diagram still does not show a force exerted on M1 by the spring.

physics1000
haruspex said:
What answer did you get? It bothers me that your diagram still does not show a force exerted on M1 by the spring.
Oh the one in the picture is wrong.
I thought it is meaningless to post an answer, since no one tried to answer :/
but anyway, I got it solved, thanks anyway :)

physics1000 said:
Oh the one in the picture is wrong.
I thought it is meaningless to post an answer, since no one tried to answer :/
but anyway, I got it solved, thanks anyway :)
It's not that nobody tried. I had to go out for a while. Using a forum provided by volunteers you need to be patient.

haruspex said:
It's not that nobody tried. I had to go out for a while. Using a forum provided by volunteers you need to be patient.
I didnt blame you or something, you don't have any commitment to answer to me ( sorry if you felt so because of what I wrote ). I wasnt mad or anything about it ( now I understand what I wrote looks like, sorry about it ), just thought it was matterless.
Problem is, now to write all I wrote in latex here.. its hell lol. ( I will edit the comment with the picture, say it is wrong and delete picture ).
Thanks anyway :)

## 1. How does a vertical spring connected between two bodies with a rope work?

The vertical spring connected between two bodies with a rope is a system that utilizes the elasticity of a spring to connect two objects and allow for vertical movement. When one object moves up or down, the spring stretches or compresses, creating a force that pulls or pushes the other object in the opposite direction.

## 2. What factors affect the behavior of a vertical spring connected between two bodies with a rope?

The behavior of a vertical spring connected between two bodies with a rope is influenced by several factors, including the stiffness of the spring, the weight and mass of the objects, and the length of the rope. These factors determine the amount of force and displacement that the spring will experience.

## 3. How do you calculate the force exerted by a vertical spring connected between two bodies with a rope?

The force exerted by a vertical spring connected between two bodies with a rope can be calculated using Hooke's Law, which states that the force is directly proportional to the displacement of the spring. The formula is F = -kx, where F is the force, k is the spring constant, and x is the displacement.

## 4. Can a vertical spring connected between two bodies with a rope be used to measure weight?

Yes, a vertical spring connected between two bodies with a rope can be used as a scale to measure weight. By knowing the spring constant and the displacement of the spring, the weight of an object can be calculated using the formula W = kx/g, where W is the weight, k is the spring constant, x is the displacement, and g is the acceleration due to gravity.

## 5. What are some real-life applications of a vertical spring connected between two bodies with a rope?

A vertical spring connected between two bodies with a rope has various practical applications, such as in car suspensions, bungee jumping, and weight scales. It is also used in engineering and construction to absorb shock and vibrations, and in sports equipment such as trampolines and pogo sticks.

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