The rate of doing work is called power. It is a scalar quantity. Its SI unit is Watt (W). Another common unit of a power is horsepower. Horsepower is related to watt as:
1 horsepower = 746 W = 750 W approximately.
Power =
1 kilowatt (KW) = 1000 watt
1 megawatt (MW) = 1000000 watt
1 horsepower (HP) = 750 watt (approx.)
The power is one watt when one joule of work is done in one second.
Relation between Work, Energy and Power
Work, energy and power are interrelated terms. Actually, the capacity to do work is a power which comes from energy. When a person does a work then he loses some amount of energy. We get energy from food. Our body stores chemical energy and transforms it into muscular energy. We use that muscular energy to do work.
The rate of doing work is power. If we work faster then power is increased. If higher energy is applied to do work then work done becomes faster and power will also get increased. So, work, energy and power are interrelated terms.
The rate of doing work is power. The SI unit of power is watt (W).
If one joule of work is done in 1 second, it is said to be one watt. The relation is:
KW = 1000watt (10³ watt)
1MW = 1000 000 watt (10^{6} watt)
1 HP = 746 watt (approximately 750 watt)
The relation among work, energy and power are:
Power is defined as the rate of doing work.
A body is said to have one watt power when it does one joule of work in one second.
A body is said to have unit power if it does unit work in unit time.
A 60 kg person climbs stairs of total height 20 m in two minutes. Calculate the power of the person.
\begin{align*} \text {Solution,} \\ \text {The work done in climbing a height of 20m is} \\w &= m \times g \times h \\ &=60 \times 9.8 \times 20\\ &= 11760 J\\ \text {Power delivered is} \\ P &= \frac wt \\ &= \frac {11760}{120} \\ &= 98\: W \\ \text {Therefore, the power of person is} \: 98 \: W \\ \end{align*}
\begin{align*} \text {Solution,} \\ \text {force} \: (F) &= 75 N \\ \text {distance} \: (d)&= 20 m \\ \text {time} \: (t)&= 100 sec \\ \text {power}\:(P) =?\\ \text {Now,} \\ p &= \frac wt \\ &= \frac {75 \times 20}{100} \\ &= 15\: J \\ \text {Thus, the power of crane is}\: 15\: N\\\end{align*}
\begin{align*} \text {Here,} \\ \text {Power} \: (P) &= 2\: KW = 2\times 1000 = 2000\: J/s \\ \text 60\: \text {seconds, electrical energy is converted into heat energy,} \\ &= 2000 \times 60 \\ &= 120, 000\: \text {Joule} \\ &= 120\: KJ \\ \end{align*}
\begin{align*} \text {Here,} \\\text{Force}\:(F)&= 3000\: N\\\text{distance}\:(d)= 5\:m \text {Work done} \: (W) &= F \times d = 3000 \times 5 = 15000\:j \\ \text {Time taken}\: (T) &= 10 s \\ \text {Power} \: (p) = ? \\ \text {we have,} \\ \text {Power} \: (P) &= \frac WT &= \frac {15000\: J}{10\: s} \\ &= 1500\: J/s = 1.5\: KW \\ \end{align*}
The SI unit of power is ______.
joule
dyne
watt
Newton
There is ______ watt in 1 horsepower.
The correct formula to calculate the power is ______.
P=t+w
P=t / w
P=w/t
P=w-t
The rate of doing work is ______.
pressure
speed
work
power
If 1 Joule of work is done in 1 second, the power is said to be ______.
2 erg power
1 joule power
3 pascal power
1 watt power
Whose value depends on time?
Power
Energy
Work
Pressure
ASK ANY QUESTION ON Power
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Sunil
What is power ?
Jan 10, 2017
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