Concepts of Physics

IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

Kinetic Energy of Marbles


To learn the concept of energy


At the school level, the concept of different types of energies are introduced. The potential and kinetic energy are prominent one.


two aluminium channels of different lengths, two marbles, a towel


Spread the towel on the floor. Place the channels in such a way that their heights remains the same and they touch the floor with same inclination. If you release the two balls simultaneously, it will be observed that they rolled down and go to the same distance.


When we raise the two bodies to the same height, their potential energies (\(mgh\)) remains same. As the body rolls down, the potential energy is gradually converted into kinetic energies (\(\frac{1}{2}mv^2\)). At the point where the ball strikes the floor, all the potential energy is converted into kinetic energies. Neglecting any loss due to friction, \(mgh\) is equal to \(\frac{1}{2}mv^2\). From this simple equation, it can be calculated that velocity for the marbles at the end of the channels will be same. As velocity is same for both the balls, they will go up to the same distance.