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: Angular momentum Question

  1. Jan 7, 2012 #1
    1. The problem statement, all variables and given/known data
    Harry Potter is sitting 2.0 meters from the center of a merry-go-round when Draco Malfoy casts a spell that glues
    Harry in place and then makes the merry-go-round start spinning on its axis. Harry has a mass of 50.0 kg and can
    withstand 5:0 g's of acceleration before passing out. What is the magnitude of Harry's angular momentum when
    he passes out?

    2. Relevant equations
    T=I alpha

    3. The attempt at a solution

    Assuming that the spell is a force then rF = I alpha. And using alpha = a/r, we using the max acceleration of 5g that
    5mgr = Ia/r
    However I'm not sure where to go from this, how do i get v? as time is unknwon
  2. jcsd
  3. Jan 7, 2012 #2
    Lets look at the second eqn you mentioned,
    you have m,r. what you need is v

    Now, what do you think the acceleration 5g is acting along (direction)?
  4. Jan 8, 2012 #3
    oh i see mv^2/r = ma a=5g :D
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook