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Homework Help: Two masses connect by a rope over unequal slopes

  1. Sep 16, 2012 #1
    Hey Guys,

    I'm stuck with two particular problems that relates to two masses attached by a rope on a slope with unequal angles and i'm unsure how to go about the problem, I have never accounted a problem such as these before and i'm stuck with how to go about it. I have taken two photos of the questions as they include a diagram!

    Thanks in advanced.

    1. The problem statement, all variables and given/known data

    Q.9 and Q.19 are those I am refering to in the attachments.

    2. Relevant equations

    I believe looking at all the forces affecting the diagram, Tension, Gravity, Weight components, ultimately to my understanding ƩF=0 for the block to remain at rest, that is the forces balance. I am a bit confused on how to set out some of the forces as most problems I have encounted similar to this have a 90 degree angle where the block on the left is.

    3. The attempt at a solution

    I do not have answers to these two questions as they are not provided with the text book

    Attached Files:

  2. jcsd
  3. Sep 16, 2012 #2
    For each mass try writing sum of all forces in x and y direction. [and show us how you wrote them]

    Without going into calculations my intuition tells me the system will move to the left. [if there is no friction, can you tell what is the friction needed to keep the system at rest?]
  4. Sep 16, 2012 #3
    I don't know, i'm confused, I know the only possible forces that can act is tension and weight components but I don't know how to set it out. Here is an attempt anyway


    x: mgcosθ
    y: T-mgsinθ

    x: T-mgcosθ
    y: T-mgsinθ
  5. Sep 16, 2012 #4
    1. Draw the system with all the forces, you don't need x and y as for both the masses all the relevant forces are in 1 dimension, choose the direction parallel to the slope. [in the other dimension sum of all forces are 0...]
    2. Don't forget the Newton laws.
    3. You will have 2 equations with two unknowns, do you know what they are?

    Let your intuition help you.
    Hint: What can you tell about a? [[itex]\sum F=ma[/itex]]
  6. Sep 16, 2012 #5
    Another hint, for each mass draw its own diagram and choose the coordinate system parallel to the slope.
    Last edited: Sep 16, 2012
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