At a certain point in time, the total energy of a closed system is observed to be 90 J. Which one of the following statements is TRUE?
1. Twelve hours later the energy of the system is 90J
2. Three hours later the energy of the system is 180J.
3. Some of the energy should be potential
4. Twelve hours later the energy of the system is 45J
5. All of the energy should be kinetic if the objects are moving.