A 1.1 kg book is lying on a 0.74 m-high table. You pick it up and place it on a bookshelf 2.2 m above the floor.

How much work does gravity do on the book?

Known variables:

mass (m):

height 1 (h1): .74 m

height 2 (h2): 2.2m

Height difference: 2.2 – .74= 1.46

displacement x force:

mass x gravity x height

1.1kg*9.8*1.46 = 17.6 J

Since gravity is forcing down, it would be negative!

W1= -17.6

2) How much work does your hand do on the book?

Same answer as the previous question but a positive force.

W2= 17.6