91Ó°ÊÓ

The energy possessed by an object by virtue of its motion is known as kinetic energy.For Example, the motion of a yo-yo, stretching a rubber band, moving the muscles, a moving car, etc.

The kinetic energy is proportional to the mass and square of the velocity of the object. Its formula is given by:

\(KE = \frac{1}{2}m{v^2}\)

The energy stored in an object by virtue of its position above the surface of the earth is known as gravitational potential energy.

It is given by:

\(PE = mgh\)

Here, m is the mass of the object, h is the height, and g is the acceleration due to gravity \(9.8\;{\rm{m/}}{{\rm{s}}^{\rm{2}}}\).

When the skier is standing still at the top of the hill, he/she has no kinetic energy. The potential energy is the maximum, which is stored in the gravitational field between the skier and the earth.

As the skier coasts downhill, the potential energy gets converted into kinetic energy. If the skier is lifted higher, he/she would have greater potential energy.

Therefore, the more the steepness, the more will be the potential energy. Consequently, a skier starting from a greater height will move at a greater speed.

Thus, (c) and (d) depict the highest speed when friction is ignored.