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«Физика пәнін ағылшын тілінде оқып үйрену»

33. Power.

In daily life we hear about powerful cars, nuclear power or the power of motors. People usually talk about the power of men, animals and machines. So what is the meaning of power?
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“Power” has a special meaning in physics, like “work” and “energy”. The following example may be useful in understanding the word “power”.

Let us suppose that we are constructing a building as shown in the figure on the left. There are two workers to carry up 200 bricks, which weigh 600 kg, to the third floor of an apartment, which is 9 m vertically above the ground. One of the works can carry up the bricks in one hour, but the other can carry them up in two hours. If we ask which of them is the more powerful, what will the answer be? Of course the answer will be the first one, because he does the same work in a shorter time than the other.

In scientific terminology, power is defined as the amount of work done (or energy spent) in a unit of time. It can be stated as:

_Power_Work done

^orPower 

Energy spent

in symbols,

Time

taken

Time

taken

P  ^W

t

or _P_^Et

Work is measured in newton – metre or joule and time in second, and then the unit of power is N m/s or J/s and has a special name: watt (W). 1 watt is 1 joule energy consumed in 1

second:

Watt  1

Joule

sec ond

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