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Alex works at a legal firm which produces a lot of documents. Often Alex has to carry heavy stacks of documents from one office to another. On this particular day Alex, who weighs 75 kilograms, has to transport a stacks of documents which weighs 10 kilograms. He has to lift them 5 meters from the floor and then carry them to an office 100 meters down the hall, where he will drop them on the floor. Alex walks swiftly at a steady rate of 1 meter per second. What two pieces of information given in the above description will help you compute the amount of work Alex does when he lifts the papers?



Answer :

thompzac
You would need the weight of the paper and how high off the ground Alex is going to be lifting them.
AL2006

All you need in order to calculate the work done is the force exerted vertically ("lifting") and the vertical distance through which the force is exerted ("height").
Then  Work = (force) times (distance).

Sadly, if you try to apply this simple definition of 'work' to the data you've given
for the situation, your attempt will fail ignominiously.  You will say that Alex
has exerted a force of 10 kilograms to lift the documents 5 meters, and has
therefore done (10 x 5) = 50 somethings of work, which is wrong.

It's wrong because 'kilogram' is a unit of mass, not one of force.
Nothing 'weighs' 10 kilograms.

But my first paragraph is the direct answer to your question.  The mass
of the stack of documents, and the height to which the stack is lifted, will
help you compute the amount of work Alex does.


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