A kid slides down an icy (frictionless) hill starting from rest. At the top his gravitational potential energy is 500 J.
-He slides part way down the hill to a point where his gravitational potential energy is 200 J.His kinetic energy at that point will be
A)200 J.
B)300 J.
C)some unknown value between 0 and 500 J.
D)none of the above.

Question

Quizplus · Accepted Answer

According to the law of conservation of energy, the total energy of the system remains constant. At the top of the hill, the kid has only potential energy which is 500 J. As he slides down, this potential energy is converted into kinetic energy. At the point where his potential energy is 200 J, the remaining 300 J of energy must be in the form of kinetic energy. Therefore, the correct choice is B - his kinetic energy at that point will be 300 J.

A Kid Slides Down an Icy (Frictionless) Hill Starting from Rest