1. Not finding help here? Sign up for a free 30min 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!

Rotational KE Problem

  1. Jan 14, 2006 #1
    In a crude model of a rotating diatomic molecule of chlorine (Cl2), the two Cl atoms are 2.00x10^-10 m apart and rotate about their center of mass with angular speed = 1.40x10^12 rad/s. What is the rotational kinetic energy of one molecule of Cl2, which has a molar mass of 70.0 g/mol?

    I have tried this problem but I really don't even know where to start..
     
  2. jcsd
  3. Jan 14, 2006 #2

    siddharth

    User Avatar
    Homework Helper
    Gold Member

    What is the forumla for Rotational Kinetic energy of a an object?
     
  4. Jan 14, 2006 #3
    KE=1/2* I* (angular speed)^2

    I=1/12*m*L^2

    would mass=140 g?
     
  5. Jan 14, 2006 #4

    siddharth

    User Avatar
    Homework Helper
    Gold Member

    Why have you chosen I = 1/12* m*l^2? Are you approximating this as a rod of length L? I don't think that's a good idea becuase most of the mass is concentrated in the atom, not the bond. So I think taking this as two sepearate Cl atoms rotating about the COM is a better idea

    Also, the mass will not be 140g. The mass of 1 mol of Cl2 is 70 grams. And you know 1 mol of Cl2 contains around 6.023*10^23 molecules. So what is the mass of 1 molecule?
     
  6. Jan 14, 2006 #5
    ok i got the mass of one to be 1.16E-22

    But then what equation for moment of inertia would I use?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Rotational KE Problem
  1. Rotation problem (Replies: 3)

Loading...