Advertisements
Advertisements
Question
The moon is revolving around the earth in a circular path. How much work is done by the moon?
Solution
Work done by the moon is zero as the force of attraction on the moon by the earth is normal to the direction of motion of the moon.
APPEARS IN
RELATED QUESTIONS
Soni says that the acceleration in an object could be zero even when several forces are acting on it. Do you agree with her? Why?
A coolie does no work against the force of gravity while carrying a luggage on a road.
Define the term energy.
MULTIPLE CHOICE TYPE
In an electric cell which in use, the change in energy is from:
Explain degradation of energy by taking two examples of your daily life.
How much work is done when a force of 2 N moves a body through a distance of 10 cm in the direction of force?
What happens to the work done when the dispacement of body is at right angles to the direction of force acting on it? Explain your answer.
Why does a spanner have a long handle?
A boy does work when he pushes against a brick wall. (yes/no).
Define 'joule'.
Can every force produce work?
A cricket ball is thrown up from the earth's surface. What happens to its P.E.
(a) during the motion
(b) at the highest point?
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.
In what way does an ‘Ideal machine’ differ from a ‘Practical machine’?
Name the material commonly used for the manufacturing of solar cells.
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.
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.
