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प्रश्न
Give one example in which a force does zero work.
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उत्तर
Work done by the earth on a satellite moving around the earth is zero, as the direction of the motion of the satellite is always perpendicular to the direction of the gravitational force.
संबंधित प्रश्न
No work is done by a force if the body
State the S.I. unit of work and define it.
State two factors on which the work done on a body depends.
It takes 20 s for a person A of mass 50 kg to climb up the stairs, while another person B does the same in 15 s. Compare the work done.
Name the forms of energy which a wound-up watch spring possesses.
State two advantage of producing hydroelectricity.
State two disadvantages of producing hydroelectricity.
Name the physical quantity whose SI unit is Nm.
A man carrying a suitcase in his hand is walking horizontally. What is the work done against gravity?
Write an expression for work done by a force depends?
An object is dropped from a height H. when is its
(i) P.E. maximum,
(ii) K.E. maximum,
(iii) P.E. = K.E.?
State the energy changes which take place when Water stored in the dam is used to turn turbine in dynamo.
State the energy changes which take place when A stone dropped from the top of a cliff reaches the ground after some time.
Can two agents, doing the same work, have different power?
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]
A girl of mass 40 kg runs a height of 80 stairs, each 25 cm high with a load of 20 kg on her head in 25 sec. If g is 10 m/s2, find:
(i) Gravitational force acting on the girl.
(ii) Work done by her.
(iii) Useful work done by her.
(iv) Her power in watt.
Who is the odd one out?
Look at the activity below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
A donkey is carrying a load on its back.
