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: [FBD] Stick balancing

  1. Nov 20, 2008 #1
    1. The problem statement, all variables and given/known data

    Find the linear and angular accelerations given that FA is the applied force.
    v is the current linear velocity and w is the current angular velocity.
    r is the radius of the stick.
    h is length of the stick.
    d is angle from the vertical axis.

    2. Relevant equations
    a = dv/dt; linear acceleration
    u = dw/dt; angular acceleration
    Icenter = m h2/12; moment of inertia of stick

    3. The attempt at a solution
    Sum of horizontal forces:
    m ax = -FA
    ax = -FA/m

    Sum of vertical forces:
    may = -mg + FN = 0

    Sum of torque
    T = I u = 0.5 h FN sin(d) - 0.5 h FA cos(d)
    u = 0.5 h ( mg sin(d) - FA cos(d) ) / ( m h2/12 )
    u = ( 6 / m h )( mg sin(d) - FA cos(d) )

    Is this correct?

    Shouldn't the vertical acceleration be non-zero? Because if w and u are non-zero, and the finger maintains at the same height, then the center of mass of the stick must be moving. What is wrong with the above?

    - Thanks
    And thank you for replying to my other thread. There are so many threads I thought I shouldn't bump the one that was solved.
  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