An easy physics question?

Question

The sum of the kinetic and potential energies of a system of objects is conserved

Choose one answer.

a. only when the objects move along closed paths

b. none of these are correct answers

c. always

d. only when no external force acts on the objects Incorrect

e. only when the work done by the resultant external force is zero

i really dont no which answer...is correct

Answer 1

If a system have maximum kinetic energy than the potential energy is zero, and conversed.

Answer 2

the correct answer is E.

If you have a system of objects where the work done by the resultant external force is zero, then there is no energy added or removed from the system, therefore the sum of kinetic and potential energies remains constant, for that "represents" the amount of energy in the system.

Answer 3

c

Answer 4

d