On a roller coaster potential energy builds up while you are going up a hill . Once at the top all of that energy is being released this giving you a push which means all of that energy is making you down down the hill. Hope this helps you.
Well first of all, a planet doesn't have a semimajor axis, although it's orbit does.
In an orbit with a smaller semimajor axis, the planet moves faster, and its orbital period is shorter.
That's why the International Space Station circles the Earth in less time than the Moon does.
A. The slope represents the rate of increase in elevation in feet per minute.
b. The elevation is increasing with time so we are hiking uphill.