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: Mechanics application problem

  1. Mar 16, 2010 #1
    1. The problem statement, all variables and given/known data
    When an athlete
    throws a javelin her forearm snaps through an angle of
    approximately ¼ radians in 0.20 s. The athlete’s hand moves
    with approximately constant speed, the length of her forearm
    is 45 cm, and the combined mass of her forearm and javelin
    is 2.0 kg. Assuming that the system is well approximated by
    a mass of 2.0 kg located 45 cm from the pivot, what force do
    the ligaments holding the forearm to the elbow need to exert?

    2. Relevant equations

    3. The attempt at a solution

    Im getting lost, I cant interpret the question easily. I really have no idea how to do this.
    I can picture some sort of lever mechanism but other than that, im confused as to what to do with the angular displacement value and the time period value theyve given us.

  2. jcsd
  3. Mar 16, 2010 #2
    Looks more like a centripetal force problem to me, unless I am reading it wrong. I am no biology expert, but I believe the ligaments are attaching the forearm with the elbow so it will experience a force due to the circular motion of the javelin. You will need to calculate this force based on what you know about centripetal acceleration.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook