Question

i'll give a medal if someone could help & explain?
You place a book on top of a spring and push down, compressing the spring by 10 cm. When you let go of the book, it is pushed up by the spring. Which statement describes what happens to the energy of the spring-book system?

A. The gravitational potential energy of the system increases.
B. The elastic potential energy of the system increases.
C. The kinetic energy of the system decreases.
D. The total energy of the system increases.

Answer 1

Also provide your attempt (that'll make it easier to explain).

Answer 2

My guess would be B since it is a spring? @LastDayWork

Answer 3

I think the question is not clear whether it is about step
(a) "...You place a book on top of a spring and push down..."
(b) "...When you let go of the book,..."

Answer 4

i think it means when you pick it up off of it, but i do see what you're saying. @LastDayWork

Answer 5

^^ You mean step (b) ?

Answer 6

Try to answer for both the steps separately.

Answer 7

i dont think i understand what to answer?
like what energy happens you set the book down, or pick it up? @LastDayWork

Answer 8

I think the question refers to the end of the process, for which the kinetic energy of the system has increased at the cost of the potential energy in the compressed spring.

Answer 9

Consider only one case at a time.

Answer these (for spring-book system) -
Fill in the blanks with (increase/decrease/remain same)
For case (a)
-The gravitational potential energy of the system will _________
-The elastic potential energy of the system will ____________
-The kinetic energy of the system will ___________
-The total energy of the system will _____________
For case (b)
-The gravitational potential energy of the system will _________
-The elastic potential energy of the system will ____________
-The kinetic energy of the system will ___________
-The total energy of the system will _____________

Answer 10

I still thin they would all be wrong except B, considering it goes does then jumps up as you take it off. @LastDayWork correct or no?

Answer 11

& as @douglaswinslowcooper said the kinetic increases, not decreases

Answer 12

I just don't know what part of the process the question refers to. Compressing the spring increases its potential energy, decreasing gravitational potential energy. Releasing the spring produces motion, thus increasing kinetic energy, at the cost of spring potential energy but with some gain in gravitational potential.

Answer 13

^^ @abbyisaprincess Now try to fill the answers.

Answer 14

1)decrease
2)increase
3)increase
4) remain the same?
@LastDayWork

Answer 15

For case (a) or (b) ??

Answer 16

wouldnt they be the same? @LastDayWork

Answer 17

Read douglaswinslowcooper's post again.

Answer 18

i agree, and i think i understand what he was saying.
what do you think the question is asking for? @LastDayWork

Answer 19

In general, questions usually ask about the later process.

Answer 20

so when the spring pushes back up, which would make the elastic potential energy of the system increase? @LastDayWork

Answer 21

-When an object is taken away from earth - its gravitational potential energy increases.
-When a spring is pushed/pulled away from its natural length - its elastic potential energy increases
-When a mass gains velocity - its kinetic energy increases
-When work is done on the system - its total energy increases
(and vice-versa)

Answer 22

if the book is taken away, that would mean its gravitational potential energy increases? so that would make the answer A? @LastDayWork

Answer 23

but its not taken away from earth.
is it the same thing?

Answer 24

The book is not taken away, actually the system is left on its own. It is the spring that pushes the book away.

Answer 25

I believe it is A, personally @LastDayWork

Answer 26

Yes, A is the right answer.