Big Jim had been experimenting in space with the gravitational pull of the moon. in this case he had jumped off of the surface of the moon, however as Newton's first law states Big Jim would have just went sailing through space if not for the outside force, this case being gravity emitted by the moon.
Newton's first law of motion: An object in motion will stay in motion and a object at rest will stay at rest unless acted upon by an outside force. Here a satellite passes planets not effected by friction going on endlessly until acted on by an outside force.
The gravity of the moon pulling down on Big Jim was not enough to squash him that is why he could stand. in order to jump Big Jim needs to exert a force greater than that of the gravity.
Newton's second law of motion: The amount of acceleration an object has is directly proportionate to the force and mass of an object. for instance a satellite was launched out of the earth's gravitational pull.
As Big Jim Jumped off of the moon the moon exerted a force of it's own pushing on Big Jim.
Moon's pull on Jimmy
Newton's third law of motion simply states that: for every action or force there is an opposite reaction that happens. in this case the astronaut Big Jim jumps off the moon but the moon also pushed on Big Jim, since Jimmy is off the ground it meant that he had more force than the moon when it pushed on Big Jim.