# A kid slides down an icy (frictionless) hill starting from rest. At the top his gravitational...

## Question:

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

## Conversion of Energy:

From the conservation of energy, we know that the energy can neither be created nor destroyed it can only change its form. Therefore, when the object's potential energy will decrease, then its kinetic energy will increase.

Given data

Initial energy of the kid {eq}(E_{1} ) = 500 \ J {/eq}

Energy at the second place

{eq}E_{2} = P + K \\ E_{2} = 200 + K \ J {/eq}

where

• P is the potential energy
• K is the kinetic energy

Now applying the energy conservation

{eq}E_{1} = E_{2} \\ 500 = 200 + K \\ K = 300 \ J {/eq}

Therefore, the kinetic energy of the kid would be 300 J.

Hence the correct option would be "b".

Energy Conservation and Energy Efficiency: Examples and Differences

from Geography 101: Human & Cultural Geography

Chapter 13 / Lesson 9
104K