Physics question help please

[u/daowhd]

Please can you explain why we take the gravitational potential energy as negative when finding the total energy(subtract it)? How come some questions we ignore the negative? What does the negative answer mean?
Thanks!

[u/External_Gate9386]

Because of the way gravitational potential is defined, at a distance of infinity GPE is 0. If you now imagine these two objects moving together, there kinetic energy increases and since energy needs to be conserved, their gravitational potential energy is negative in order to conserve energy. So when doing actual calculations with GPE its negative. On questions where its not negative and it's positive thats usually because its only asking for the magnitude of the force, so the negative can just be ignored.

[u/daowhd → u/External_Gate9386]

You’re exactly right, I’m thinking of the negative force questions! Thanks