I exactly want to know that what does work mean? if a person carrying a bag but he is standing he is not doing any work because bag did not cover any displacement in the direction of force but if a person is walking then did he do any work or not?
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Basic Terminology of Work explains it pretty well. – Jan 28 '17 at 17:32
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3Very relevant: Why does holding something up cost energy while no work is being done? which addresses the difference between physics work and 'Man, this is tiring!' work. – dmckee --- ex-moderator kitten Jan 28 '17 at 18:09
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-1. No research effort. This question has been asked many times on this site. – sammy gerbil Jan 28 '17 at 20:34
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Work can said to be done only when there is a displacement in the direction of applied force. If a person carrying a bag walks horizontally,then the gravitational force is in vertical downward direction and displacement in horizontal direction. Here force and displacement are in mutually perpendicular direction.There is no displacement in the direction of applied force(force applied against gravitational force).Hence workdone is zero. If the person is moving in vertical direction then there will be displacement in the direction of applied force.Hence there will be work.
SARANJITH P
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if there is no force been applied on the bag horizontally then how does bag change its position when the man walks carrying that bag ? – Remy Jan 28 '17 at 17:46
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@Remy is right. Of course there is work done when walking horizontally (even when not carrying something). Your foot pushes you forward and your body moves in that direction. If you are carrying a bag, it is also pushed forward. – Lewis Miller Jan 28 '17 at 17:54
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If man applying a force and there is a displacement in the direction of that force then there is work. – SARANJITH P Jan 28 '17 at 17:55
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While there is a good web page explaining it as @Countto10 said (and there is no need to answer), your answer, I think, is a restatement of the question itself. – AHB Jan 28 '17 at 19:29
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Work is every interaction between a system and its environment that can be described as lifting of weight.
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Well regarding man carrying the bag horizontally, it is only the gravitational force that does no work. The man, of course, does work on the bag by displacing it horizontally, but gravitational force does zero work in the horizontal movement as it is acting vertically.
Allen
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