Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Angular Speed (w)

  1. Mar 23, 2008 #1
    A thin, uniform, rectangular sign hangs vertically above the door of a shop. The sign is hinged to a stationary horizontal rod along its top edge. The mass of the sign is 2.40 kg and its vertical dimension is 45.0 cm. The sign is swinging without friction, becoming a tempting target for children armed with snowballs. The maximum angular displacement of the sign is 25.0° on both sides of the vertical. At a moment when the sign is vertical and moving to the left, a snowball of mass 520 g, traveling horizontally with a velocity of 160 cm/s to the right, strikes perpendicularly the lower edge of the sign and sticks there.

    (a) Calculate the angular speed of the sign immediately before the impact

    I have absolutely no clue on how to the w. If anyone can please enlighten me, it would be greatly appreciated. Thanks

  2. jcsd
  3. Mar 24, 2008 #2

    Shooting Star

    User Avatar
    Homework Helper

    Use conservation of angular momentum at the moment of impact.

    The sum of the angular momenta of the snowball and the sign just before the impact is equal to the angular momentum of the sign just after the impact. If you need more help, you have to show some work now, though this should be enough.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook