Find the acceleration of 3 blocks and tensions

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Homework Help Overview

The discussion revolves around determining the acceleration of three blocks with varying masses (1 kg, 2 kg, and 3 kg) and the tensions in the connecting strings (T1 and T2). The problem is set in a context involving pulleys and gravitational forces.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants explore relationships between tensions and accelerations, with some suggesting the introduction of additional variables. Questions arise regarding the setup of the problem, including the conditions under which it is being analyzed (e.g., Earth vs. Moon) and the nature of the forces acting on the blocks.

Discussion Status

The discussion is ongoing, with participants sharing insights and questioning assumptions. Some have proposed simplifications and additional variables to clarify the problem, while others express uncertainty about their progress. No consensus has been reached, but there is a collaborative effort to explore the problem further.

Contextual Notes

Participants note potential missing information and the need for relevant equations. There is also a discussion about the nature of the forces acting on the blocks and the role of the pulleys in the system.

avistein
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Homework Statement



In the figure shown.Find :
a)acceleration of 1 kg,2kg,and 3kg blocks and
b)tensions T1 and T2

The Attempt at a Solution


2T1=2T2=>T1=T2
T2=1*a ,where a is acceleration of mass 1kg
T2=a
Let ar be the acceleration of mass 2 kg and 3kg wrt to the 3rd pulley.then,
3g-T1=3ar
and T1-2g=2ar
solving ar=g/5
net acceleartion of 2 kg and 3kg is a-ar and a+ar
then what to do?
 

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Complicated affair. My degree might not be enough, but who knows...
I think we need some relevant equations. Could you collect them for us ?
And then perhaps some given info too. This thing on Earth or on the moon ?
Is T1=T2 a law of physics ?

Is T2 ending up in the middle of the pulley an accidental error? Or is that a spool of wire that is being held in place by the 1 kg weight.
Perhaps you want to introduce some more intermediary variables.
 
How are you getting along with this one ?
I gather you succesfully completed the two-block exercise, this is a bit more challenging.
 
Not done. I am still struggling with this.
 
avistein said:
Let ar be the acceleration of mass 2 kg and 3kg wrt to the 3rd pulley.then,
3g-T1=3ar
No. The mass doesn't 'know' anything about the motion of the pulley. It feels two forces and it accelerates accordingly.
 
We start with a simplification: the lower pulley only, static. later we let that part accelerate downwards, but first we have to discover something. We follow the advice in post #2: introduce T3 and T4. And we make a drawing.
 

Attachments

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Wow, I see posts cross again. avi still awake ? Or at work / school?.

No matter, both helpers are useful to you. I continue with the simple case: the lower pulley only, static.

My questions are:
1. What other forces are there? So there is clearly no balance. And yet T1 = T3 (remember: pulleys only change force direction, not magnitude).
2. Can you calculate the acceleration ?
3. So what is T1?
4. Then: what is T4?

You can read up on this in links on Atwood's machine. The link even has a calculator, but you only want to use it to check things. Remember: you want to understand this. The numerical answer is only a side benefit, not a goal in itself.
 
Last edited:

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