Ch 11: Using Energy

Question 1

The work-energy equation includes work which is an energy _______. Work can be positive or negative; it’s positive when energy is transferred into a system, negative when energy is transferred out of a system.

Answer 1

transfer

p. 355

Question 2

Given the example of a water pump which has 50% efficiency, we know that a 100 J input results in a 50 J output. This transformation into thermal energy is an ________ change. There is no practical way to recover this thermal energy and convert it back to electric energy. The energy isn’t lost, but it is lost to our use.

Answer 2

irreversible

p. 356

Question 3

Generally, we can define _________ as:

e = what you get/ what you had to pay

Answer 3

efficiency

Question 4

The relatively low efficiency of the human body is due to process limitations. Estimated at about __%, the efficiency is less than 100% because of the biochemistry of how your food is metabolized and the biomechanics of how you move.

Answer 4

25

Question 5

The rather modest calculated efficiency of a power plant turns out to be largely due to a fundamental limitation: _______ ______ cannot be transformed into other forms of energy with 100% efficiency.

Answer 5

thermal energy

p. 357