Mechanics- connected particles

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Discussion Overview

The discussion revolves around the mechanics of connected particles, specifically involving pulleys, tension in strings, and the motion of masses on an incline and a horizontal surface. Participants explore the dynamics of the system, including net force equations and kinematics.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • Some participants assert that pulleys only change the direction of tension in the string and that the mass on the incline will slide down, causing the mass on the horizontal floor to move left.
  • One participant suggests setting up net force equations for each mass to analyze the system.
  • Another participant expresses confusion about calculating acceleration and seeks clarification on the dynamics involved.
  • Several participants provide equations for the forces acting on the masses, indicating that both masses experience the same magnitude of acceleration.
  • One participant calculates acceleration and speed for one of the masses, while another mentions a scenario where tension is zero due to a broken string.
  • Links to external resources are shared for further reference.

Areas of Agreement / Disagreement

Participants generally agree on the role of pulleys and the need for net force equations, but there is uncertainty regarding specific calculations and the implications of a broken string. The discussion includes multiple viewpoints on how to approach the problem.

Contextual Notes

Some participants express confusion about the calculations and the relationships between forces, acceleration, and tension, indicating that assumptions and definitions may vary among contributions.

Who May Find This Useful

Students and individuals interested in mechanics, particularly those studying connected systems involving pulleys and forces.

Shah 72
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20210531_213908.jpg

I have no clue how to do this. Pls help
 
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The pulleys only act to change the direction of the tension in the connecting string.

It should be obvious that the mass on the incline slides down the inline, making the mass on the horizontal floor move left … no way the system moves otherwise.

Set up two net force equations like the ones I’ve set up previously, one for each mass.

You need to start taking ownership of these problems.
 
skeeter said:
The pulleys only act to change the direction of the tension in the connecting string.

It should be obvious that the mass on the incline slides down the inline, making the mass on the horizontal floor move left … no way the system moves otherwise.

Set up two net force equations like the ones I’ve set up previously, one for each mass.

You need to start taking ownership of these problems.
Thank you! The pulley ones are a bit confusing. I need to practice more on these kind of problems.
 
skeeter said:
The pulleys only act to change the direction of the tension in the connecting string.

It should be obvious that the mass on the incline slides down the inline, making the mass on the horizontal floor move left … no way the system moves otherwise.

Set up two net force equations like the ones I’ve set up previously, one for each mass.

You need to start taking ownership of these problems.
 
Last edited:
skeeter said:
The pulleys only act to change the direction of the tension in the connecting string.

It should be obvious that the mass on the incline slides down the inline, making the mass on the horizontal floor move left … no way the system moves otherwise.

Set up two net force equations like the ones I’ve set up previously, one for each mass.

You need to start taking ownership of these problems.
In this
F= m×a
T- 0.2× 20cos 30-10= 2a
T- mu R= 2a.
I still don't understand how to calculate a
 
You are given that it takes 1 second for the floor mass to move 0.6m from rest. You should be able to determine the magnitude of acceleration of the floor mass with that info using a kinematics equation.

Both masses undergo the same magnitude of acceleration.

also,

forces for the mass on the incline ...

$m_1g\sin{\theta} - \mu_1 m_1 g\cos{\theta} - T = m_1a$

mass on the floor ...

$T - \mu_2 m_2g = m_2a$

Tension in the string is the same for both masses.
 
skeeter said:
You are given that it takes 1 second for the floor mass to move 0.6m from rest. You should be able to determine the magnitude of acceleration of the floor mass with that info using a kinematics equation.

Both masses undergo the same magnitude of acceleration.

also,

forces for the mass on the incline ...

$m_1g\sin{\theta} - \mu_1 m_1 g\cos{\theta} - T = m_1a$

mass on the floor ...

$T - \mu_2 m_2g = m_2a$

Tension in the string is the same for both masses.
Thanks a lot. So I get a= 1.2m/s^2 and speed of box B = 1.2m/s
 
skeeter said:
You are given that it takes 1 second for the floor mass to move 0.6m from rest. You should be able to determine the magnitude of acceleration of the floor mass with that info using a kinematics equation.

Both masses undergo the same magnitude of acceleration.

also,

forces for the mass on the incline ...

$m_1g\sin{\theta} - \mu_1 m_1 g\cos{\theta} - T = m_1a$

mass on the floor ...

$T - \mu_2 m_2g = m_2a$

Tension in the string is the same for both masses.
For q(d) tension is zero as the string breaks. So I need to calculate the acceleration for A
2a=10- 0.2× 20 cos 30 , a=3.27 m/s^2, s = 1-0.6= 0.4, v^2=u^2+2as, I get v =2.01m/s
 
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