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.
If their volumes are equal, then the denser one has more mass.
Bernoulli's principle can be borrowed from the principle of conservation of energy.
Hope this helped.
A chemical change. chemical changes could cause changes in shapes or sizes
I think 3 but I’m not sure I don’t even know who they are