   Chapter 12, Problem 51P

Chapter
Section
Textbook Problem

A 70.0-kg log falls from a height of 25.0 m into a lake. If the log, the lake, and the air are all at 300. K, find the change in entropy of the Universe during this process.

To determine
The change in entropy of the universe during the process.

Explanation

Given Info:

Mass of the log is 70.0kg .

The height from which the log falls into the lake is 25.0m .

When a log falls from a height into a lake, the potential energy of the log is converted to heat. Hence, the transfer of energy from the falling log to the lake reservoir is the loss of potential energy by the log.

Thus,

ΔQ=mgh

• m is the mass of the log
• g is acceleration due to gravity
• h is the height from which  the log falls

Hence, the change in entropy of the reservoir is,

ΔS=ΔQT=mghT

Substitute 70.0kg for m and 9.8m/s2 for g, 25

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