A coolie is Walking on a railway plat form with a load of 30 kg on his lead. How much work is done by coolie?
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Technically no work is done by him, since applied force is in the direction perpendicular to the displacement. But he is working, as the language suggests and keeping physics aside. :) :-)
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From the given information, there is no work done by the coolie. This is because there is no displacement of the luggage in the direction of force acting on it. The center of mass of the coolie also is at the same height all the time. Thus there is no work done against the Earth's gravitational force.
But, to lift the luggage / load on to the head or shoulders, the change in potential energy is the work done, before he tarts walking.
Next, we know that it is impossible to start walking, continue walking, and stop walking, if there is no friction. Hence, against friction he does work, while walking. If the coefficient of friction between the ground and the feet is about 0.33 and if he walks for 100 meters, then the work done is 0.33 * 30 * 100 * 9.8 Joules (or about 230 calories).
But, to lift the luggage / load on to the head or shoulders, the change in potential energy is the work done, before he tarts walking.
Next, we know that it is impossible to start walking, continue walking, and stop walking, if there is no friction. Hence, against friction he does work, while walking. If the coefficient of friction between the ground and the feet is about 0.33 and if he walks for 100 meters, then the work done is 0.33 * 30 * 100 * 9.8 Joules (or about 230 calories).
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This needs further deliberation. what about the displacement of load? How come energy is consumed with out any work?
there is a displacement of load from ground to a a height, when it is lifted. When it is carried, there is work done against friction and not against gravity.. Friction exists between feet and ground. Each time feet push the ground, to maintain the speed of walking, there is energy spent.
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