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when a satellite is orbiting the earth and moves to a lower orbit, it changes kinetic and grav potential energies.

WHY is the total energy change of satellite= kinetic energy change - potential energy change ?

Also, if the satellite is going to a higher orbit, would the equation be the other way around?
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The total energy change of the satellite = kinetic energy change + potential energy change, however gravitational potential energy is defined as being 0 when the satellite is infinitely far away from the Earth, and is expressed as being negative when closer so there minus sign is within the formula for the potential energy:



$U = -\frac{GMm}{r}$
When going from a higher orbit to a lower one the magnitude of the potential energy increases, but because of the minus sign it will be more negative, so overall the change in gravitational potential energy will be negative.

If the satellite moves to a higher orbit the potential will become closer to 0, and so the overall change will be positive.

(Original post by Henny987)
when a satellite is orbiting the earth and moves to a lower orbit, it changes kinetic and grav potential energies.

WHY is the total energy change of satellite= kinetic energy change - potential energy change ?

Also, if the satellite is going to a higher orbit, would the equation be the other way around?
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