Question

A librarian lifts a 2.2 kg book from the floor to a height of 1.25 m. She carries the book 7 meters to the stacks and places the book on a shelf that is 0.35m above the floor. How much work does she do on the book?

Answer 1

Answer:

$W = 7.55\,\text{J}$

Step-by-step explanation:

To calculate Workdone we're going to use the formula:

$W = Fd$

where F = ma, and a = g = 9.81 ms^-2

$W = Fd = mgd$

m = 2.2 kg

g = 9.81

only the vertical displacement from the original position (i.e the floor) is important when it comes to calculating Workdone. So, she lifts the books 1.25m from the floor and she puts the books in the shelf which is 0.35m above the floor.

So the net distance (or displacement) from the floor is: 0.35m

hence d = 0.35m

Plugging all the values in the equation will yield:

$W = mgd$

$W = (2.2)(9.81)(0.35)$

$W = 7.55\,\text{Joules}$