KINETIC ENERGY

— Energy, in physics and mechanics, is defined as the capacity for doing work. Kinetic energy is energy due to motion, in contradistinction to potential energy, which is energy due to position or state of strain. A few examples will make these definitions clear. A stone on the top of a clifi po e es potential energy, because it can do work by falling from the top of the cliff to the bottom. Immediately, however, it is rolled over the edge of the cliff, its energy becomes partly kinetic, owing ‘to the fact that it is moving. The energy of a pendulum at the end of each stroke is wholly potential, because it is momentarily at rest, but is capable of doing work because of its position. At the middle of its stroke, it loses all its potential energy, its energy being then kinetic. At intermediate points, its energy is partly potential and partly kinetic. The energy of an arrow resting on a stretched bow is potential; as it flies through the air, the energy is mainly kinetic. <A coiled spring po e es potential energy due to state of strain; a travelling automobile po e es kinetic energy due to its motion. The kinetic energy of a body is proportional to its ma and to the square of its velocity. The kinetic energy of a swinging hammer weighing 2 lbs. is twica that of a hammer weighing 1 Ib. If swung at a velocity of 10 feet per second, its kinetic energy is one hundred times as much as if it = swung at a velocity of 1 foot per second.;