As a rocket increases height and slows down, it gains more and more potential energy and loses more and more kinetic energy. Potential energy is store energy (usually determined by height), and kinetic energy increases as speed increases.
I would say by putting two fingers under your chin or putting two fingers on the back of your wrist, hope i helped ! :)
I think it most likely burn since th metal tube is going to transfer so much heat
I think the correct answer would be to electrolyze water (run an electric current through it) to decompose it into hydrogen and oxygen. Assuming 100% efficiency, it is said that it needs about 40kWh per kilogram of water to fully decompose it.