1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

Question Confirmations.

  1. Nov 16, 2009 #1
    Hi there, I have a multiple choice quiz that I completed for my physics class and I'm looking for confirmation on whether I'm correct or not.

    1.The centre of mass of an object...
    A. Must always lie outside the object, at a point where there is no mass.
    B. May lie outside the object, at a point where no mass is.
    C. Must always lie within the mass of the object

    2. Consider a ball on the end of a string being whirled in a horizontal circle. The horizontal force acting on the ball points...
    A. outwards, away from the centre of the circle
    B. inwards, towards the centre of the circle
    C. ... nonsense. There is no force at all on the ball

    3. A man is standing on a turntable holding a dumbell in each of his outstretched hands. He is rotating at 1 rev/s. If he now brings his hands in close to his chest,
    A. his rotational speed decreases
    B. his rotational speed is unchanged
    C. his rotational speed increases

    The answers I got are B, B and C respectively. Can anyone confirm?
  2. jcsd
  3. Nov 16, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    looks good!
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook