Gravitational potential energy = the energy due to an objects

Gravitational energy is the energy of a body when it is taken to a certain height with respect to the earth surface.It is one of the part of potential energy that comes in thr part of the mechanical energy. the work done in taking a body upto a certain height get stored in the body in form of gravtitational potential energy. potential energy is directly proportional to height or altitude upto which the body is taken, mass of the body and gravtational acceleration(9.8m/s^2)So P.E. = mgh

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we need to know the time interval during which the force acts. impulse of force = momentum change

answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.