HannaTheKillerRobot
Answered

Eva is in a closed, dark room. She uses her arm muscles to turn on a lamp. When she moves her hand closer to the lamp, the light heats her hand. The light bounces off the pages of a book and into her eyes.


If this room is a closed system, what happens to the total amount of energy in the room?


A.

It remains constant.


B.

It decreases.


C.

It increases, then decreases.


D.

It increases.

Verified Answer :

Chløë14

Its a tricky one but my guess would be D if she turned on the lamp causing energy if would have increased the amount in the specificed room x

AL2006


Well, we know that the total energy in a closed system remains constant.

The problem with the story of Eva is that she is not in a closed system. 
If the dark room were really a closed system, then she could press the
button or turn the switch all day, and the lamp could not light.  It needs
electrical energy coming in from somewhere in order to turn on.

Let's say that Eva used her arm muscles to strike a match and light the
candle on the table.  Then we would have have food energy, muscle
energy, chemical energy in the match, chemical energy in the candle,
heat and light energy coming out of the candle, heat energy soaking into
her hand, light energy bouncing off of the book and into her eyes ... all
going on during the story, and the sum total of all of them would remain
constant.

Related Questions