Kinetic energy and rigid bodies

[Niles]

Homework Statement

Does it make sense to talk about kinetic energy without specifying, which axis the body is rotation about? I mean, since K = ½ * I * w^2, I have to say that " ... the kinetic energy of the body around the x-axis is ...", right?

 

[nrqed]

Homework Statement

Does it make sense to talk about kinetic energy without specifying, which axis the body is rotation about? I mean, since K = ½ * I * w^2, I have to say that " ... the kinetic energy of the body around the x-axis is ...", right?

Not only you have to say around what axis it is rotating but in addition you have to say around what point! In other words, you have to specify completely the axis around which the object rotates (and notice that the value of the moment of inertia depends on what is the axis around which the object revolves).

 

[Niles]

Ok, good - then I have understood it correctly :-)

Thanks!