Advertisements
Advertisements
प्रश्न
What is power? How do you differentiate kilowatt from kilowatt-hour? The Jog Falls in Karnataka state are nearly 20 m high. 2000 tonnes of waterfalls from it in a minute. Calculate the equivalent power if all this energy can be utilized? (g = 10 m s–2)
Advertisements
उत्तर
Power is defined as the rate of doing work or the rate of transfer of energy, Kilowatt is the unit of power and kilowatt-hour is the unit of energy or work as a kilowatt-hour
= unit of power × unit of time.
Energy possessed by 2000 tonnes
(= 2000 x 103 kg) water at a height of 20 m, Ef, = mgh
= 2000 x 103 x 10 x 20
= 4 x 108 J
Power generated if all this energy can be
utilized,
P = `"E"_"p"/"t"`
= `(4 xx 10^8 "J")/(60"s")` (∵ t = 1 min = 60 s)
= `2/3 xx 10^7 "W"`
APPEARS IN
संबंधित प्रश्न
Power spent by a body depends on the time for which it does work.
State two conditions when no work is done by a force.
A boy of weight 40 kgf climbs up the 15 steps, each 15 cm high in 10 s and a girl of weight 20 kgf does the same in 5 s. Compare:
- the work done, and
- the power developed by them. Take g = 10 N kg-1.
What are the units of (a) work, and (b) energy?
What is meant by a translational motion? Give one example.
Complete the following sentences:
1 H.P. = ........ W.
An object is dropped from a height H. when is its
(i) P.E. maximum,
(ii) K.E. maximum,
(iii) P.E. = K.E.?
How long should an electric motor, of power 2 H.P. operate, so as to pump 5 m3 of water from a depth of 15m. [Take g = 10 N kg−1]
An electric motor of power 100 W is used to drive the stirrer in a water bath. If 50% of the energy supplied to the motor is spent in stirring the water. Calculate the work done on the water in one minute.
Look at the activity below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
A wind-mill is lifting water from a well.
