1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: System of Objects

  1. Sep 23, 2008 #1
    http://img297.imageshack.us/img297/5664/systemofobjectssq1.jpg" [Broken]
    1. The problem statement, all variables and given/known data

    Find the acceleration of the system of two masses shown in the figure, given that m1 = 10 kg, m2 = 20 kg, θ = 60o and φ = 30o. Assume that the incline plane is smooth (i.e., there is no friction) and that g = 10 m/s2.

    2. Relevant equations
    A: T=m[tex]_{2}[/tex]g*sinθ + m[tex]_{1}[/tex]g*sinφ
    B: T[tex]_{1}[/tex]=T[tex]_{2}[/tex]
    C: F=ma

    3. The attempt at a solution
    T[tex]_{total}[/tex]=223.2 using A
    F=m[tex]_{2}[/tex]g*sinθ - m[tex]_{1}[/tex]g*sinφ

    Using C: a=F/m
    a=m[tex]_{2}[/tex]g*sinθ - m[tex]_{1}[/tex]g*sinφ / m[tex]_{1}[/tex] + m[tex]_{2}[/tex]
    a= 4.11m/s[tex]^{2}[/tex]

    I'm not sure how to approach this one....
    I know tension = T[tex]_{1}[/tex]=T[tex]_{2}[/tex]...
    Then i get the Force that will be going right since m[tex]_{1}[/tex] < m[tex]_{2}[/tex]
    and find the acceleration. I just want someone to see if I understood this right.
    I was trying to approach the masses as two different components, but it didn't work that well..

    Attached Files:

    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Sep 24, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Where did you get this equation?
    These make sense.

    Do this: Draw a free body diagram for each mass, showing all forces acting. Then apply Newton's 2nd law (your equation C) to each mass. Combine the two equations to solve for the acceleration.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook