The Science of Energy

Chapter LIVING ENERGY

Seventeenth-century scientists performed experiments that gave a better understanding of the energy changes that take place when an object moves. The first real experiments into the behavior of moving objects were conducted by Galileo Galilei (1564–1642), the Italian astronomer and physicist. Although Galileo could not have understood energy as we understand it today, he seems to have had an awareness that the energy of an object thrown vertically upwards, a ball say, does not gradually disappear as it reaches the top of its flight. The energy is, in fact, changing from one form into another, from energy of movement into energy of position. We now call these ideas kinetic energy and potential energy. As the object reaches its highest point all of its kinetic energy has become potential energy and for a split second the ball stops moving. As it starts to fall, the ball’s potential energy is changed back again into kinetic energy so that when it reaches the ground it has just as much kinetic energy as it had when it was first thrown up. Aristotle had said that in order to keep

moving a body had to have a force applied to it continuously. This was supposedly provided by air rushing in to fill the space left by the moving object. Later, others pointed out that if this was true then moving objects should travel faster and faster. Galileo showed that this point of view was the correct one. He measured the velocities of objects moving on slopes, on level surfaces and falling freely. He showed that an object moving down a slope or falling freely accelerates, that is, its velocity increases, but on a flat surface

A ball is given kinetic energy when it is thrown into the air. At its highest point it has no kinetic energy, but it has maximum potential energy.

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