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Calculate the velocity of a mass

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  1. Mar 12, 2016 #1
    • Member warned about not using the homework template
    Hi
    I have this question to do :

    upload_2016-3-12_16-54-39.png

    I want to calculate the velocity ... I did like this:

    m2 * a = m2 * g - T
    m1 * a = T - μ*m1*g*sin α
    combine them
    m1 * a = -m2*a + m2*g - μ*m1*g*sin α

    Now what should I do ?
    thanks
     
  2. jcsd
  3. Mar 12, 2016 #2
    why you ask? the vertical mass can cover only a finite distance ..... so the inclined plane -mass should cover the same distance as string/cable is taut..... then from above equations you can calculate the acceleration so you know speed... well i may be wrong... but one can try.
     
  4. Mar 12, 2016 #3
    ok the acceleration is

    a=(m2*g - μ*m1*g*sin α)/(m1+m2)
    and v=a/t
    but I do not have t (time)
     
  5. Mar 12, 2016 #4
    are you correct in writing above equation for 'a' and v ? think...
    connected systems have same displacements, velocity-magnitude and accelerations. v=a/t is not correct dimensionally - as it is accelerated motion with initial vel=0 one can use v= sqrt(2.acceleration. distance covered)
     
  6. Mar 12, 2016 #5

    Ray Vickson

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    Science Advisor
    Homework Helper

    If the acceleration ##a## is constant, you have a simple problem of an object falling with constant acceleration. The acceleration happens to be different from ##g## in this case, but that does not matter; the equations are exactly the same as those you must have seen already in previous courses; if not, you can solve the differential equation for the motion., to get ##x(t)##.
     
  7. Mar 12, 2016 #6
    In that case I believe that you could use the kinematic equation V2 = V02+2ax
    Assuming that the acceleration is constant which it should be since it is caused by gravity in this case
     
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