Work, energy, potential energy--mechanical and gravitational

Description
Positive and negative work has been explained beautifully. The topics like work energy theorem, mechanical energy are explained using examples.What is different here is a nice experiment performed using a ball rolling down a inclined groove from a height .Calculation shows what should be the minimum height from where the ball should roll so that it can go round a vertical circular path and indeed the motion of the ball confirms the theoretical calculation. It will be useful to go through because such kind of situation is very commonly found in the numerical examples too. Thanks to Youtube.com for the video