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- Summary
- is it just a matter of the tangential velocity?

Quick question about the relativistic energy of a rotating thin ring, hoop or cylinder. Is there any reason why the relativistic energy would be anything different than ##E=\gamma_t m_0 c^2## where ##\gamma_t## depends on the tangential velocity ##v_t## observed by someone at rest with the axis?

Likewise, is the relativistic angular momentum ##L = \gamma_t m_0 v_t r## where r is the radius?

Or is this trickier than it appears? If you spin up a ring does its invariant mass ##m_0## change? (a figure skater who increases her angular velocity by drawing her arms in changes her ##m_0## for example). I realize the radius may change but the observer can easily measure it.

Thanks in advance

Likewise, is the relativistic angular momentum ##L = \gamma_t m_0 v_t r## where r is the radius?

Or is this trickier than it appears? If you spin up a ring does its invariant mass ##m_0## change? (a figure skater who increases her angular velocity by drawing her arms in changes her ##m_0## for example). I realize the radius may change but the observer can easily measure it.

Thanks in advance