Worked examples In accordance with the principle of conservation of energy, the whole of this potential energy becomes transferred to kinetic energy when the stone reaches the ground again. Hence kinetic energy on reaching the ground = 56.25 J. Answer. P.E. at greatest height During a shunting operation, a truck of total mass 15 metric tonnes (t) moving at […]
Kinetic energy We saw on page 36 that, w here there are no opposing forces. a moving body needs no force to keep it moving with a steady velocity. If, however, a resultant force does act on a moving body in the direction of its motion, then it will accelerate and the work done by the force will […]
To measure personal power Anyone may find the power he or she is able to develop when running upstairs by measuring the total vertical height of a stairway and using a stop-watch to find the time taken to run up it. The result is creditable to the boy, but it must be remembered that he can maintain this […]
Power and its units Machines may be classified by the speed with which they transfer energy or do work thps-there are motor-car engines of small “power”, as they are rated, or large power (Power is defined as the rate of transfer of energy, energy transferred or average power = time taken The SI unit of power is called […]
Thermonuclear energy At the present time research is being carried out to investigate the possibility of obtaining energy by the fusion of hydrogen nuclei to form heavier ones. This is called a thermonuclear reaction and is believed to be the source of the sun’s energy. Under the extremely high-temperature conditions in the interior of the sun, hydrogen nuclei fuse […]
The conservation of energy and mass Early in the twentieth century Albert Einstein put forward new ideas regarding the relationship between space, time, mass, and energy which have come to be known as the theory of relativity. It had long been accepted that matter could not be destroyed. This assumption was expressed in the law of conservation of […]
The future of nuclear power installations Nuclear reactors like most other industrial plants do not last for ever and, at the time of writing (1988) plans are in operation for decommissioning the early Magnolia reactors. The Berkeley one, mentioned in Fig. 7.6 on page 80 is one of the first for demolition. The first advanced gas-cooled reactor (AGR) […]
Nuclear energy We have just discussed the energy changes which lead to the generation of electricity in a coal-burning electric power station. In a nuclear electricity generating installation the heat required for raising steam is provided by a nuclear reactor instead of a coal furnace. Fig. 7.5 is a simplified diagram to show how a reactor works. It […]
The sun as a source of energy The interesting to trace back to their origin the series of energy transfers which lead the release of light energy by pressing an electric switch. The light is given out from a thin incandescent tungsten filament inside a glass The internal energy required to raise the temperature’ of the tungsten wire is derived […]
Heat energy At this point it will be advantageous to say a word about the meaning of the term heat. In everyday life we sometimes loosely refer to the “heat energy in a body”, instead of using the term: “internal energy”. In physics, heat is defined as energy which is transferred from one place to another owing to a […]