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Work, Energy And Power

Question

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Define power. State its SI and cgs units.

Solution

The rate of doing work is called power.
i.e.    $P equals limit as increment t rightwards arrow 0 of fraction numerator capital delta W over denominator capital delta t end fraction equals fraction numerator d W over denominator d t end fraction$

Since,    $d W equals F with rightwards arrow on top times stack d s with rightwards arrow on top$
∴    $P equals fraction numerator d W over denominator d t end fraction equals F with rightwards arrow on top times fraction numerator stack d s with rightwards arrow on top over denominator d t end fraction equals F with rightwards arrow on top. v with rightwards arrow on top$
The SI unit of power is Watt and cgs unit is erg/s.

Some More Questions From Work, Energy and Power Chapter

Define watt.

How many joules are there in one eV?

What is the relation between kWh and Joule?

Does the body at rest possess energy?

By eating two apples, a person starts pushing the wall of room. If food value of apple is 100 calories per apple, how much work he will do in pushing the wall in one hour?

A man is rowing upstream and is at rest w.r.t. shore. Is he doing work w.r.t. shore?

Is frictional force conservative?

What is the work done by gravitational force in taking the mass m with constant velocity through height h?

A mass is tied with a string and whirled in horizontal circle. What is the work done by tension force?

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