%Mass
Ar C = 12 g/mol, Mr C₄H₁₀ = 58 g/mol, Ar H = 1 g/mol

or

Both create energy. Both require atoms.
Fission is ripping the atoms apart, fusion is forcing them together. Fission takes less energy because it's easier to rip unstable atoms apart but pushing two atoms that have similar charges together is extremely hard. Fission is currently mainstream on earth, but fusion is known for taking place within stars.
So you don't jump off a cliff thinking you could fly. Laws and Motion are heavily used in jobs and help us understand more about the mechanics of how earth's gravity operates. Imagine in the future where we could manipulate gravity? That's why we learn and study this so much.