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: Linkage kinetics problem

  1. Jun 10, 2012 #1
    1. The problem statement, all variables and given/known data

    The linkage ABD is formed by connecting two 8.05-lb bars and a collar of negligible weight. The motion of the linkage is controlled by the force applied to the collar. Knowing that a tthe instant shown the angular velocity and angular acceleration of bar B are zero and 10 rad/s2 counterclockwise, respectively, determine the force P.

    http://img685.imageshack.us/img685/5416/picxv.png [Broken]

    2. Relevant equations

    [tex]\sum \tau = I\alpha[/tex]
    [tex]\sum F = m a_G[/tex]
    [tex]\vec a_G = \vec a_B + \vec a_{G/B}[/tex]

    3. The attempt at a solution

    Considering the vertical bar (1):
    [tex]a_B = \alpha_1 L[/tex]
    [tex]\tau = LF = I\alpha_1 \Rightarrow F = \frac{I\alpha_1}{L} = \frac{mL\alpha_1}{3}[/tex]

    Now, the horizontal one (2):
    [tex]a_{Gx} = a_B = \alpha_1 L[/tex]
    [tex]P\cos \theta - F = ma_{Gx} = m \alpha_1 L \Leftrightarrow P \cos \theta = m\alpha_1 L (1 + 1/3) \Leftrightarrow P = \frac{4m \alpha_1 L}{3\cos \theta} [/tex]

    I know this isn't correct (it doesn't match the solutions), but I can't figure out what I'm doing wrong.

    Last edited by a moderator: May 6, 2017
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted