Jupiter has mass

PHYSICS · Multi-part · Fermi University Physics · Mechanics & Dynamical Systems · Rotation, rigid bodies and accelerated frames · Gravitation and central-force motion

Action and Symmetry, Ch Non-inertial frames from one Lagrangian

Problem

Jupiter has mass MJ=1.898×1027 kgM_{\rm J} = 1.898\times10^{27}\ \mathrm{kg}. Its moon Europa orbits at a distance d=6.71×108 md = 6.71\times10^{8}\ \mathrm{m} from Jupiter's centre. Take Cartesian axes centred on Europa with the xx-axis pointing from Europa towards Jupiter's centre, and treat Jupiter as a point mass. ((a)) Write down the tidal tensor Tij=GNMJ(δij−3ninj)/d3T_{ij} = G_{\rm N}M_{\rm J}(\delta_{ij}-3n_in_j)/d^3 of Jupiter's field evaluated at Europa's centre, giving TxxT_{xx}, TyyT_{yy}, TzzT_{zz} and stating that the off-diagonal components vanish in these axes. ((b)) Verify that the trace of TijT_{ij} is zero.

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