450 Relativity*P39.48Let observer A hold the unprimed reference frame, with uc134=and uc234= −. Let observer B be atrest in the primed frame with ′ ==−−uuvu v c111201vuc==134.(a)Then ′ =−−=−−− −+=−+uuvu v cccccc222213434134341 519 16bgbg.speed =′ ===uccc23225 1624250 960..(b)In the unprimed frame the objects, each of mass m, together have energyγγmcmcmcmc22222210 753 02+=−=...In the primed frame the energy is mcmcmc222221010 964 57−+−=.., greater by4 573 021 5122...mcmc=times greater as measured by observer B.Section 39.9Mass and EnergyP39.49Let a 0.3-kg flag be run up a flagpole 7 m high.We put into it energymgh=≈0 3720.kg 9.8 msmJ2ej.So we put into it extra mass∆mEc==×=×−2821620310210Jm skgejfor a fractional increase of210101615×−−kg0.3 kg~.P39.50E=×
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