Why 3 dof for a particle and not 6 including rotation

Join the discussion
Registration is free. Start your own thread to ask a follow-up.
Sign up Log in
1 reply · 2K views
babbar.ankit
Messages
4
Reaction score
0
A particle has 3 degree of freedom (dof) , so we write 3N dof for N particles...
But I have a fundamental doubt: 3 dof means we consider only transitional motion of particle?
... why can't we say 6 dof?
 
Physics news on Phys.org

Discussion

Because, in classical mechanics, a particle is said to have zero spatial extent, and hence, insofar it rotates about an axis going through its C.M, the whole particle lies on the axis of rotation and thus do not have any rotational energy in addition to its translational energy.

Thus, in classical mechanics, rotation of infinitesemal particles is dynamically irrelevant.