Titlebook: Mastering Science; Robert Barrass Textbook 1991Latest edition Macmillan Publishers Limited 1991 community.energy.environment.evolution.gen

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Energy, work and power,The universe consists of matter and energy. Science, therefore, is the study of both matter and energy. In contrast to matter, which occupies space and has mass, energy does not occupy space and it has no mass. . may be defined as . or as ..

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,Air: Earth’s atmosphere,Earth’s atmosphere is a mixture of colourless gases (see Figure 11.1), held near Earth by the pull of Earth’s gravity. You cannot see air, but you feel it when the wind blows, when you move quickly through still air, and as you breathe deeply.

refine

Machines,.. We need to consider only simple machines.

釋放

Energy from sunlight,You will remember that in sunlight green plants add oxygen to the air. In 1860, about 100 years after Priestley’s work on the effects of plants and animals on the composition of air (see page 118), a German botanist Julius von Sachs demonstrated that in sunlight green leaves increase in mass.

eucalyptus

fodlder

Matter and energy from your food,Of the 94 elements that occur naturally, only about 22 (all of low atomic mass) are essential constituents of living organisms.

instate

recession

Ledger

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