Calculating Work Done by Gravity on a Moved Book

  • Thread starter Thread starter talaroue
  • Start date Start date
  • Tags Tags
    Book Table
AI Thread Summary
To calculate the work done by gravity on a book lifted from a height of 0.99 m to 2.43 m, the correct approach involves using the equation Wmg = mg(Yi - Yf). The initial poster initially misapplied the equation, mistakenly calculating the work done by their hands instead of gravity. The key realization was that the work done by gravity is negative when lifting the book, as gravity opposes the motion. Correcting the sign in the equation resolves the confusion. Understanding the distinction between the work done by gravity and the work done by the person lifting the book is crucial for accurate calculations.
talaroue
Messages
302
Reaction score
0

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?
 
Physics news on Phys.org
talaroue said:

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...
 
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.
 
I just posted as you posted yeah, thanks for the help!
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Thread 'Egg Drop Challenge! Need ideas for winning designs'

I was thinking using 2 purple mattress samples, and taping them together, I do want other ideas though, the main guidelines are; Must have a volume LESS than 1600 cubic centimeters, and CAN'T exceed 25 cm in ANY direction. Must be LESS than 1 kg. NO parachutes. NO glue or Tape can touch the egg. MUST be able to take egg out in less than 1 minute. Grade A large eggs will be used.
View full post »

Similar threads

Work Done by Gravity and Tension in a Pulley System
Replies
3
Views
2K
Find the force to push a book sideways on a table
Replies
2
Views
2K
How Does Elevator Physics Affect the Work Done by a Cable?
Replies
2
Views
2K
Work done against gravity with reducing gravity......
Replies
10
Views
2K
Work of gravity on an object sliding down a frictionless sphere
Replies
12
Views
2K
Calculating Applied Force for a Moving Block on a Table
Replies
9
Views
4K
Work done on a pendulum by gravity
Replies
7
Views
3K
Integral for work done leading to potential energy sign confusion
Replies
5
Views
2K
How Is Work Calculated with a Nonconstant Force?
Replies
10
Views
2K
What is the work done on cart by the string?
Replies
1
Views
2K

Hot Threads

Recent Insights

Back
Top