Help with 3 objects/masses connected by string over frictionless pulley?

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Homework Help Overview

The problem involves three masses connected by strings over a frictionless pulley, with specific values for each mass and the acceleration due to gravity. The original poster seeks to find the downward acceleration of one of the masses based on their attempts to apply Newton's second law.

Discussion Character

  • Exploratory, Problem interpretation, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to analyze the system using free body diagrams and equations of motion. They express confusion over the signs of their calculated acceleration and explore different equations to find a solution.

Discussion Status

Some participants express a desire for assistance, indicating a lack of clarity in the problem setup. The original poster has made several attempts to solve the problem but has not reached a satisfactory conclusion. One participant requests a diagram to better understand the configuration, while another notes they have figured it out, suggesting some progress has been made.

Contextual Notes

There is mention of a diagram that is crucial for understanding the problem, which may not have been initially available to all participants. The original poster's confusion about the signs in their calculations indicates potential misunderstandings regarding the direction of forces and acceleration.

miamirulz29
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Homework Statement


Three masses connected by light strings are shown in the figure below (I will try my best in describing the figure):
There is light, frictionless pulley with two masses, M2 and M3, on the left and one mass, M1, on the right. They are all connected by light strings. Given m1 = 10 kg, m2 = 7.48 kg, m3 = 8.01 kg, and g = 9.8 m/s2. The acceleration of gravity is 9.8 m/s2 . Find the downward acceleration of m2 mass. answer in units of m/s^2


Homework Equations


SigmaF= ma
mg=fg

The Attempt at a Solution



I drew three separate free body diagrams for each of the masses.
For M1:
Ft-MG=MA
Ft-98=10a

For M2:
MG-Ft=MA
7.48(9.8)-Ft=7.48a
73.304-Ft=7.48a

So I combined the two equations and got -1.413 m/s^2. I though because it is downward, I didn't need the negative, so I put in UT, 1.413, it was wrong, I also put -1.413, it was also wrong. Then I tried using M3 and combined the acceleration of M3 and M2, which was 8.387, which is also wrong. Then I read on another thread that you can use the equation:
A= [(M1-M2)/(M1+M2)] * G. I got 1.413. I honestly don't know what to do at this point, can somebody please help me. Thanks in advance.
 
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Anybody? Please?
 
miamirulz29 said:
Anybody? Please?

If you could post the diagram that would help a lot so we would know where to start...
 
Diagram posted. It is on the last page, number 018 (part 1of 3).
 

Attachments

Please can anybody help? I even posted the diagram.
 
Nevermind, figured it out.
 

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