Advertisements
Advertisements
प्रश्न
A boy weighing 40 kg carries a box weighing 20 kg to the top of a building 15 m high in 25 seconds. Calculate the power. (g = 10 m/s2)
Advertisements
उत्तर
Mass of the boy, (m1) = 40 kg
Mass of the box, (m2) = 20 kg
Height, (h) = 15 m
Acceleration due to gravity, (g) = 10 m/s2
Time taken, (t) = 25 s
Total mass of the system,
M = m1 + m2
=> M = 40 + 20 = 60 kg
So, work done by the boy is,
W = mgh
=> W = (60)(10)(15)
=> W = 9000 J
Now, we can calculate the power of the boy as,
Power = `"Work done"/"Time"`
So ,
Power = `9000/25` W
= 360 W
So, the power is 360 W.
संबंधित प्रश्न
Define 1 watt of power.
What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer.
An electric heater is rated 1500 W. How much energy does it use in 10 hours?
Find the energy in joules consumed in 10 hours by four devices of power 500 W each.
How much is the mass of a man if he has to do 2500 joules of work in climbing a tree 5 m tall? (g = 10 m s−2)
Define kilowatt-hour.
The power output of an engine is 3kW. How much work does the engine do in 20 s?
An electric heater uses 600 kJ of electrical energy in 5 minutes. Calculate its power rating.
In loading a truck, a man lifts boxes of 100 N each through a height of 1.5 m.
How much energy is transferred when one box is lifted?
Which one of the following statements about power stations is not true?
