IF the toss was straight upward, then the kinetic energy it got
from the toss is the gravitational potential energy it has at the top,
where it stops rising and starts falling.
Potential energy = (mass) x (gravity) x (height)
= (0.15 kg) x (9.8 m/s²) x (20 m)
= 29.4 kg-m²/s² = 29.4 joules .
The second law states that the total entropy can never decrese over time for an isolated system
Mechanical energy can have mechanical systems. The only mechanical system in the list is the compressed spring. A car battery and a glowing incandescent lightbulb have electrical energy, a nucleus of atom has potential (internal) energy.
