What has a higher total energy?

Join the discussion
Ask a follow-up here, or get your own question answered by working scientists, mathematicians and engineers — people, not an autocomplete.
Real named experts · corrections over time · the nuance an AI answer skips
4 replies · 2K views
jakeginobi

Homework Statement


Why does a satellite that has a 40.0kg mass in its 177km orbit has a total energy larger than its 144 km orbit?

Homework Equations


Ep = -GMm/r, Et = -GMm/2r

The Attempt at a Solution


I figured from using the Et equation, the greater the radius the bigger the value, but I don't know how to explain it in terms of potential energy and kinetic energy. Also its path is a circular orbit and there's friction involved
 
Physics news on Phys.org
jakeginobi said:

Homework Statement


Why does a satellite that has a 40.0kg mass in its 177km orbit has a total energy larger than its 144 km orbit?

Homework Equations


Ep = -GMm/r, Et = -GMm/2r

The Attempt at a Solution


I figured from using the Et equation, the greater the radius the bigger the value, but I don't know how to explain it in terms of potential energy and kinetic energy. Also its path is a circular orbit and there's friction involved

You have a negative value for ##E_t##, which I assume is kinetic energy.
 
PeroK said:
You have a negative value for ##E_t##, which I assume is kinetic energy.
Total energy.

Basically: it takes energy to move the satellite to infinity. More energy than the kinetic energy (namely twice as much).

The further out you start, the easier it becomes ==> total energy is larger at 177 than at 144 km up.