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Kinetic Energy

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  p-71

2025-11-03

456

When the head strikes the pile, the work that had been stored up as potential energy in raising the head to its position of rest becomes available on account of the velocity acquired in the fall. This form of energy which is dependent upon the velocity of a body is called kinetic energy. The work that has been done on a body to give it a certain velocity is a measure of its kinetic energy. We have already learned that work = force × distance, and that force (in absolute units) = mass × acceleration; hence we may write as an expression of kinetic energy,

K.E. = FS = Ma S.

But (Formula 4) S = 1/2 at² ; hence K.E. =1/2 Ma²t², and since v = at (Formula 3)

K.E. = 1/2Mv²

in which v is the velocity per second, and K.E. is expressed in absolute units.

If K.E. is to be expressed in gravity units,

  whence

Since g (at New York) is 32.16 ft., the formula may be written