1.

there are 2 formulas for escape vel,in what condition should we use the first formula and where should we use the second?

Answer»

уσυ нєℓρ !!!  when SATELLITE is at earth surface thentotal energy = PE + KEPE = -GMm/R     , (KE)i = ?                       (M is mass of earth )TE = (KE)i - GMm/R           .....1                  (R is radius of earth) when satellite escapes from earths gravitational field then it reaches to infinity ...total energy finally = TE = KE + PEPE = GMm/r          ( r is infinity )PE = 0 , (KE)F = ?TE = (KE)f  +  0 = (KE)f   .............2 since energy is conserved so eq 1 equals eq 2-GMm/R + (KE)i = (KE)f   (KE)i  = GMm/R +  (KE)f        .................3from this eq we can see that if (KE)f is 0 then (KE) intial is minimum value of energy should be GIVEN to satellite so that it escapes out...now , (KE)i = mv2/2 ,  (KE)f = 0 , putting these VALUES in eq 3 we getv = (2GM/R)1/2this is the required RESULT...



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