Lift a small block in the air. The block has the potential to do work by virtue of its position in the air. It possesses potential energy. The potential energy of the block is due to gravity. Other examples of potential energy are a wound spring, a taut bowstring, a stretched rubber band and an inflated balloon.
Kinetic energy Let the block fall.
The block has kinetic energy, the energy of movement as it falls, and has the ability to do work. Potential energy is converted into kinetic energy. The kinetic energy in this example is also due to the force of gravity. The most efficient means of transportation in terms of energy utilization is the bicycle. To cover one kilometre, a cyclist expends 20 to 100 times less energy than a car driver.