Ratio of two masses connected by pulley

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SUMMARY

The discussion centers on calculating the ratio of two masses, m1 and m2, connected by a massless and frictionless pulley, while considering the effects of acceleration (a), the coefficient of kinetic friction (μ), and the angle (θ). The correct formula for the mass ratio is established as m1/m2 = (g(Cosθ - μSinθ))/(g - a), correcting the initial error where the denominator was mistakenly written as (g/a). The participants emphasize the importance of accurately resolving forces acting on both masses to derive the correct relationship.

PREREQUISITES
  • Understanding of Newton's second law (Fnet = ma)
  • Knowledge of frictional forces (Ff = μN)
  • Familiarity with gravitational force equations (W = mg)
  • Basic trigonometry involving angles (Cosθ and Sinθ)
NEXT STEPS
  • Study the derivation of forces in pulley systems with varying angles.
  • Learn about the effects of friction on inclined planes in physics.
  • Explore advanced applications of Newton's laws in multi-body systems.
  • Investigate the role of acceleration in dynamic systems involving pulleys.
USEFUL FOR

Students studying physics, particularly those focusing on mechanics and dynamics, as well as educators looking for examples of problem-solving in pulley systems.

Tasha9000
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Homework Statement

[/B]
Figure 1) Block 1, of mass m1, is connected over an ideal (massless and frictionless) pulley to block 2, of mass m2, as shown. Assume that the blocks accelerate as shown with an acceleration of magnitude a and that the coefficient of kinetic friction between block 2 and the plane is μ.

Find the ratio of the masses m1/m2.
Express your answer in terms of some or all of the variables a, μ, and θ, as well as the magnitude of the acceleration due to gravity g.
MLD_2l_2_v2_2_a.jpg

Homework Equations


Fnet=ma
Ff=muN
W=mg

The Attempt at a Solution



+ /x is direction of acceleration

Forces on m2

y-axis
N - mgy=0

x-axis
T - m2gx-Ff=m2a

T - m2g Cosθ - μm2Sinθ=m2a

Forces on m1

m1g - T = m1a

Attempt

I just put all the equations into one and got:

m1/m2=(g(Cosθ - μSinθ))/(g/a)

but it still says it's wrong. It says the final answer doesn't depend on Cosθ or Sinθ
 
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Tasha9000 said:

Homework Statement

[/B]
Figure 1) Block 1, of mass m1, is connected over an ideal (massless and frictionless) pulley to block 2, of mass m2, as shown. Assume that the blocks accelerate as shown with an acceleration of magnitude a and that the coefficient of kinetic friction between block 2 and the plane is μ.

Find the ratio of the masses m1/m2.
Express your answer in terms of some or all of the variables a, μ, and θ, as well as the magnitude of the acceleration due to gravity g.
MLD_2l_2_v2_2_a.jpg

Homework Equations


Fnet=ma
Ff=muN
W=mg

The Attempt at a Solution



+ /x is direction of acceleration

Forces on m2

y-axis
N - mgy=0

x-axis
T - m2gx-Ff=m2a

T - m2g Cosθ - μm2Sinθ=m2a

Forces on m1

m1g - T = m1a

Attempt

I just put all the equations into one and got:

m1/m2=(g(Cosθ - μSinθ))/(g/a)

but it still says it's wrong. It says the final answer doesn't depend on Cosθ or Sinθ

it should be m1/m2=(g(Cosθ - μSinθ))/(g-a)

I also probably messed up the components but I tried both ways
 
To check whether I have sin and cos the right way round, I consider an extreme case, like ##\theta=\pi/2##. Do your equations look right for that case?
 

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