work and energy class 9 ncert exemplar | work and energy class 9 ncert exemplar best solutions

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#workandenergyclass9ncertexemplar
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hello students in this video we had solved question number 25 to 28 of class 9 ncert exemplar

25. 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 water
falls from it in a minute. Calculate the equivalent power if all this energy
can be utilized? (g = 10 m s–2)
26. How is the power related to the speed at which a body can be lifted? How
many kilograms will a man working at the power of 100 W, be able to lift at
constant speed of 1 m s–1 vertically? (g = 10 m s–2)
27. Define watt. Express kilowatt in terms of joule per second. A 150 kg car
engine develops 500 W for each kg. What force does it exert in moving the
car at a speed of 20 m s–1?
28. Compare the power at which each of the following is moving upwards
against the force of gravity? (given g = 10 m s–2)
(i) a butterfly of mass 1.0 g that flies upward at a rate of 0.5 m s–1.
(ii) a 250 g squirrel climbing up on a tree at a rate of 0.5 m s–1.