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How to find the amount of work done on an object 
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#1
Dec1508, 04:45 PM

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1. The problem statement, all variables and given/known data
A student librarian picks up a 2.2 kg book from the floor to a height of 1.10 m. He carries the book 7.9 m to the stacks and places the book on a shelf that is 0.35 m above the floor. How much work does he do on the book? 2. Relevant equations work=force(netdisplacement)=mg*(.35) 3. The attempt at a solution work = ?(7.91.1) work = ?(6.8) = 2.2(.35) 


#2
Dec1508, 05:01 PM

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#3
Dec1508, 05:15 PM

P: 24

g = 2200 mg = 2,200,000 


#4
Dec1508, 05:35 PM

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How to find the amount of work done on an object
The work done on an object is the dot product of the Force acting on the object and the distance over which it acts. What oldgranpappy was trying to convey is that you should be only considering the forces that acted on the book along the direction over which work was done against a force. For instance work in picking up something against gravity is the product of its weight and the height that you pick it up to. How far you carry it, since that direction is perpendicular to the force of gravity, then does not affect the amount of work against gravity. 


#5
Dec1508, 05:56 PM

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m is not 1.10 or 7.9. m is the mass of the book. what is the mass of the book? 


#6
Dec1508, 06:37 PM

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#7
Dec1508, 06:52 PM

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P: 39,339

And g is the acceleration due to gravity, 9.81 m/s^{2}, so what is the weight of the book, mg?
And lifting it a tota vertical distance of 3.5 m (NOT 1.1+ 3.5 m. Do you see why?) what work is done on the book? 


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