In the above video we can see Roi sitting on his
skateboard on the upper side of the street, when he lift up his legs his skateboard
starts to roll down the street, when he wants to stop his skateboard movement, Roi
pull down his legs so that they have contact with the side walk and the skateboard
To his amaze, when he teach his shoes, he can feel
that they are hotter then they were before he used then to stop his skateboard.
What is the source of energy that caused Roi's shoes
to hat up?