a person jumping on a trampoline
a rocket blasting off from Earth
a log rolling down a hill
all of the above
This is College Physics Answers with Shaun Dychko. In all of these cases, the electromagnetic strong and weak forces can be ignored. The strong and weak force only apply on the scale of an atom, inside the atom and the electromagnetic force can apply on a large scale. But it wouldn't in these cases because we're not dealing with things that are significantly charged one way or another. So all of the above is the answer here and it's mainly an issue of the size, the scale here because gravity is a large force on a large scale. It's only a small force when you consider inside a molecule. Inside an atom gravity is negligible. But in this case we're dealing with a person and a rocket blasting up from earth and a log rolling down a hill, all of which are large scale phenomena and so that excludes the nuclear forces and electromagnetic force won't be an issue here because -- I mean, electromagnetic force would be keeping all of the molecules within the person together, and all the molecules within the rocket bonded together, that's true. But when dealing with the interaction between the rocket and the earth, it's gravity that is most important and likewise for the other, A and C.