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Motion In Straight Line

Question
CBSEENPH11020610

Infinite number of bodies, each of mass 2 kg are situated on x-axis at distance 1m, 2 m, 4 m, 8 m, respectively from the origin. The resulting gravitational potential due to this system at the origin will be

  • -G

  • negative 8 over 3 G
  • negative 4 over 3 G
  • -4G

Solution

D.

-4G

The resulting gravitational potential is,
space space space space space straight V space equals space minus 2 straight G space open square brackets 1 over 1 plus 1 half plus 1 fourth plus 1 over 8 plus... close square brackets
rightwards double arrow space straight V space equals space minus 2 straight G space open square brackets 1 plus 1 half plus 1 over 2 squared plus 1 over 2 cubed plus... space close square brackets
rightwards double arrow space straight V space equals space minus 2 straight G space open parentheses 1 plus 1 half close parentheses to the power of negative 1 end exponent
rightwards double arrow space straight V space equals space minus fraction numerator 2 straight G over denominator open parentheses 1 minus begin display style bevelled 1 half end style close parentheses end fraction
space space space space space space space space space equals space minus fraction numerator 2 straight G over denominator open parentheses begin display style bevelled 1 half end style close parentheses end fraction
space space space space space space space space space equals space minus space 4 straight G