# Physics

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the question is to write down a relationship for the potential energy of a body of mass m, when it is a distance r from the center of mass M and radius R.explain all symbols used

and show that if a body is to escape the gravitational influence of the planet, it must be launched from the surface of the planet with a minimum speed, v = (8 pi GR^2 p/3) ^1/2 ..where G is grav. const, and p is the density of the planet

• Physics -

PE= GMm/r ....see the law of gravitation.

1/2 mv^2=GMm/r

remember that density=M/(4/3 PI r^3)

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