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NEET-XII-Physics

exam-1 year:2016

with Solutions -
Qstn# 7 Prvs-QstnNext-Qstn
  • #7
    At what height from the surface of earth the
    gravitation potential and the value of g are
    -5.4 × ``10^7 J kg^{-2}`` and ``6.0 ms^{-2}`` respectively ?
    Take the radius of earth as 6400 km :
    (1) 2600 km
    (2) 1600 km
    (3) 1400 km
    (4) 2000 km
    digAnsr:   1
    Ans : 1
    Sol. V =
    +
    -GM
    R h
    = -5.4 × 107 ..... (1)
    and g =
    + 2
    GM
    (R h)
    = 6 ..... (2)
    dividing (1) and (2)
    &implies;
    ï‚´
    =
    +
    75.4 10
    6
    (R h)
    &implies; R + h = 9000 km so h = 2600 km