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प्रश्न
In which of the following cases, is work being done?
(i) A man pushing a wall.
(ii) a coolie standing with a load of 12 kgf on his head.
(iii) A boy climbing up a staircase.
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उत्तर
Work is done only in case of a boy climbing up a stair case.
संबंधित प्रश्न
Find the kinetic energy of a body of mass 1 kg moving with a uniform velocity of 10 m s-1.
A max X goes to the top of a building by a vertical spiral staircase. Another man Y of the same mass goes to the top of the same building by a slanting ladder. Which of the two does more work against gravity and why?
Ravi applied a force of 10 N and moved a book 30 cm in the direction of the force. How much was the work done by Ravi?
What is the ratio of SI units to CGS units of 'work'?
Give an example
Electrical energy changes of sound energy.
(i) A 200g ball is thrown vertically upward with an initial velocity of 30 ms-1. Draw a velocity-time graph for the motion of ball.
(ii) How long will the ball take to reach the highest point?
(iii) What will be the kinetic energy of ball, when it returns to the starting point, neglecting the air resistance?
(iv) What will be the potential energy of ball at highest point?
Calculate the work done when:
A 5 kg weight is lifted 10 m vertically. (g = 9.8 m/s2)
A coolie is pushing a box weighing 1500 N up an inclined plane 7.5 m long on to a platform, 2.5 m above the ground.
(i) Calculate the mechanical advantage of the inclined plane. (ii) Calculate the effort applied by the coolie.
(iii) In actual practice, the coolie needs to apply more effort than what is calculated. Give one reason why you think the coolie needs to apply more effort.
A force of F = (5y + 20) `hat"j"` N acts on a particle. The work done by this force when the particle is moved from y = 0 m to y = 10 m is ______ J.
