Answer: The correct answer is C.
Explanation:
According to the law conservation of the mechanical energy, the total mechanical energy in a closed system remains constant in the absence of friction.
In the given problem, a child is sliding down a slide at the playground.
When a child is on the top of the slide then the he has more potential energy. When he starts slides down the slide then the kinetic energy starts increasing.
At the bottom of the slide, he has more kinetic energy.
But some energy is lost here due to friction. Hence, the mechanical energy is not conserved.
Therefore, the correct option is C.
