Book on table moved to Shelf

  • Thread starter talaroue
  • Start date
  • #1
303
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Homework Statement


A 1.7 kg book is lying on a 0.99-m-high table. You pick it up and place it on a bookshelf 2.43 m above the floor.
How much work does gravity do on the book


Homework Equations


Wmg=mgYi-mgYf


The Attempt at a Solution



I thought that is the correct equation so I simply just plugged and chugged but it came out wrong. What did I do wrong?
 

Answers and Replies

  • #2
berkeman
Mentor
58,154
8,200

Homework Statement


A 1.7 kg book is lying on a 0.99-m-high table. You pick it up and place it on a bookshelf 2.43 m above the floor.
How much work does gravity do on the book


Homework Equations


Wmg=mgYi-mgYf


The Attempt at a Solution



I thought that is the correct equation so I simply just plugged and chugged but it came out wrong. What did I do wrong?

It might just be a sign error. Note that the question asks for the work done by gravity on the book. But the postive work done is by the person lifting the book....
 
  • #3
303
0
Sorry guys I jumped the gun on this one. I soon realized that I just had to reverse my orginal equation. The equation that I have is for the work done by your hands picking the book up.
 
  • #4
303
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I just posted as you posted yeah, thanks for the help!
 

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