1. Not finding help here? Sign up for a free 30min 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!

Determine the Acceleration of Collar B as a result of Collar A

  1. Feb 5, 2013 #1
    1. The problem statement, all variables and given/known data
    Collars A and B slide along the fixed right-angle rods and are connected by a cord of length L = 7 m. Determine the acceleration of collar B when y = 2.2 m if collar A is given a constant upward velocity vA = 2.66 m/s. The acceleration of B is positive if to the right, negative if to the left.

    I have attached an image

    2. Relevant equations

    x2+y2 = l2


    3. The attempt at a solution[/b

    I found the distance x, from the base of the support to B to be 6.64529 m

    I took the derivative of the Pythagorean to get:

    2xx' + 2yy' = 0

    Then I took the derivative again:

    2x'x' + 2xx" + 2y'2 + 2yy"

    Solving for x" = -x'2 - y'2 -yy"/x

    x" = -(-yy'/x)2 - y'2/x

    x" = -0.9057

    But it says it's wrong. Where is my mistake?
     

    Attached Files:

  2. jcsd
  3. Feb 5, 2013 #2

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member


    (I'm assuming you are using the prime to mean differentiation with respect to time.)

    I'm with you to here, although, for this problem, y'' = 0 .

    This should be
    x'' = (-x'2 - y'2 - yy'')/x

      = (-x'2 - y'2)/x​

    attachment.php?attachmentid=55404&d=1360110757.png
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook