love sersh

I think there's no absolute conclusion of friction yet , some scientist say it's the rough surface that causes the friction, while others say it's the forces between molecule . (Actually in tiny scale , noting is perfectly smooth)

I mean I have no idea how to unlock you answer, just tell me which to click

It's in trash can

Sorry,I'm new here,could you tell me how to unlock it?

Are you talking about the TWIN PARADOX? It's due to the change in inertial reference. And if acceleration is considered, you should use GR to calculate.(both for the man in spacecraft)

so what concept should we use to deal with the prediction of lorentz transformation？ thanks，i am just not sure about it at first

I knew that , but it's the next step ,c2 d (m2) = d(m2v2) , c2 2mdm=2mvdmv , I m just a little confused about the first one

I've just met a problem when I differentiated the mass-velocity equation. In m2(c2-v2)=m02c2 because the right one is a constant after differentiation , i got d [ m2(c2-v2) ] = 0 which means c2 d (m2) = d(m2v2) i don't think it makes sense, hope someone can help me point out the wrong step，thanks a lot！