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प्रश्न
उत्तर
The work done by the gravitational force of the sun on earth during its motion around the sun is zero because at every point, the displacement of earth is perpendicular to the gravitational force of sun i.e.,
W = Fd cos 900 = 0
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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.
Name the forms of energy which a wound-up watch spring possesses.
A body of mass 5 kg falls from a height of 10 m to 4 m. Calculate:
The loss in potential energy of the body,
Define 1 joule of work.
A person of mass 50 kg climbs a tower of height 72 metres. Calculate the work done. (g = 9.8 m s−2).
A force of 50 N acts on a body and moves it a distance of 4 m on horizontal surface. Calculate the work done if the direction of force is at an angle of 60° to the horizontal surface.
Draw a neat labeled diagram to show the direction of two forces acting on a body to produce rotation in it. Also mark the point about which rotation takes place.
P, Q and R are three forces which act as shown in fig.
The point O lies in the same plane. Given, P = Q = R = 10N
(i) Which force has the least moment about O? Give a reason.
(ii)Which force has the greatest moment about O? Give a reason.
A man carrying a suitcase in his hand is walking horizontally. What is the work done against gravity?
An electric motor drives a machine which lifts a mass of 4 kg through a height of 10 m in 5 s at a constant speed. Assuming g = 10 ms-2, calculate
(i) the amount of work done, (ii) the power of the machine.
State the energy changes which take place when A piece of magnesium wire is burnt in a jar of oxygen.
In what way does an ‘Ideal machine’ differ from a ‘Practical machine’?
Explain, why submarines are able to dive underwater as well as a sail on the surface of the water?
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]
If a ball is dropped on the sloping roof of a house, it acquires ______ and falls on the ground. That is the transformation of ______ energy into ______ energy takes place.
(kinetic, potential, motion)
