Physics, 12.02.2020 05:21 Albala

A person holds a book at rest a few feet above a table. The person then lowers the book at a slow constant speed and places it on the table. Which of the following accurately describes the change in the mechanical energy of the earth-book system?

A. the total mechanical energy is unchanged, because there is no change in the book's kinetic energy as it is lowered to the table.

B. the total mechanical energy is unchanged, because no work is done on the earth-book system while the book is lowered.

C. the total mechanical energy decreases, because the person does positive work on the book by exerting a force that opposes the gravitational force.

D. The total mechanical energy decreases, because the person does negative work on the book by exerting a force on the book in the direction opposite to its displacement.

Answers: 3

Show answers

Another question on Physics

Physics, 22.06.2019 03:30

The focal length of a relaxed human eye is approximately 1.7 cm. when we focus our eyes on a close up object, we can change the refractive power of the eye by about 16 diopters. (a) does the refractive power of our eyes increase or decrease by 16 diopters when we focus closely? explain. (b) calculate the focal length of the eye when we focus closely.

Answers: 3

Answer

Physics, 22.06.2019 11:10

Which situation will produce the greatest change of momentum

Answers: 2

Answer

Physics, 22.06.2019 11:30

Balloon a has charge q, and identical mass balloon b has charge 10q. you hang them from threads near each other. choose all of the statements with which you agree. check all that apply. a. a and b exert the same magnitude forces on each other. b. the force that a exerts on b is 10 times the force that b exerts on a. c. the angle between the thread supporting a and the vertical is < the angle between the thread supporting b and the vertical. d. the force that a exerts on b is 1/10 the force that b exerts on a.

Answers: 2

Answer

Physics, 22.06.2019 18:20

Object a has a length of 3 cm, a width of 2 cm, and a height of 4 cm. object b is dropped into a graduated cylinder. it displaces 19 ml of water. the volume of object a is: a: greater than the volume of object b b: less than the volume of object b c: equal to the volume of object b

Answers: 2

Answer

You know the right answer?

A person holds a book at rest a few feet above a table. The person then lowers the book at a slow co...

Questions