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Homework Help: Sin(Theta) or Cos(Theta) for Ramp problem

  1. Jan 26, 2016 #1
    1. The problem statement, all variables and given/known data

    The blocks shown in the figure below are connected by a string of negligible mass passing over a pulley of radius r = 0.250 meter and moment of inertia I. The block on the frictionless incline is moving up with a constant acceleration of magnitude a = 2.00 m/s2. What is the moment of inertia I of the pulley?

    2. Relevant equations
    3. The attempt at a solution
    I solved using T1- m1gcos(theta) = m1a
    Is it m1gsin(theta) or cos(theta) for the force of gravity on block one parallel to the T1 force. (like in eq. above or do i use m1gsin(theta))

    (don't help me solve the problem just want to make sure i projected the gravity on block1 correctly with the parallel force of tension)
  2. jcsd
  3. Jan 26, 2016 #2


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    I always check my own choice by considering theta=0. Would you expect the component of gravity to be 0 or mg then?
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