Register to reply 
How to find the amount of work done on an object 
Share this thread: 
#1
Dec1508, 04:45 PM

P: 24

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

HW Helper
P: 1,273




#3
Dec1508, 05:15 PM

P: 24

g = 2200 mg = 2,200,000 


#4
Dec1508, 05:35 PM

HW Helper
P: 5,341

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

HW Helper
P: 1,273

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

P: 24




#7
Dec1508, 06:52 PM

Math
Emeritus
Sci Advisor
Thanks
PF Gold
P: 39,568

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? 


Register to reply 
Related Discussions  
Find the net amount of charged contained in a cube  Introductory Physics Homework  4  
FInd the work done when a cnstant force applied to an object  Precalculus Mathematics Homework  1  
Steam turbines, maximum amount of work done?  Introductory Physics Homework  3  
How can you find out the amount of hawking radiation a black hole exhibits?  Astronomy & Astrophysics  4  
Using work to find The amount of...  Advanced Physics Homework  2 