4A. 3 part c)

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ckilkeary 2G
Posts: 68
Joined: Fri Aug 09, 2019 12:16 am

4A. 3 part c)

Postby ckilkeary 2G » Sun Feb 02, 2020 8:39 pm

Here's the full problem:
Air in a bicycle pump is compressed by pushing in the
handle. The inner diameter of the pump is 3.0 cm and the pump is depressed 20. cm with a pressure of 2.00 atm. (a) How much work is done in the compression? (b) Is the work positive or negative with respect to the air in the pump? (c) What is the change in
internal energy of the system?

Part c) is the part I'm getting stuck on. What I've seen in the book in their examples is that ΔU = w . So why is the answer in the book for part c) 8 J instead of of 28 J ? and how is that calculated?

Jesalynne 2F
Posts: 100
Joined: Wed Sep 18, 2019 12:18 am

Re: 4A. 3 part c)

Postby Jesalynne 2F » Sun Feb 02, 2020 9:13 pm

I am pretty sure you are correct and the answer should be 28 J. I found an old post on chemistry community and that was said to be the correct answer. Also, in my solution manual (old one but the same question) the answer is 28 J.
Older post with this question: https://lavelle.chem.ucla.edu/forum/viewtopic.php?t=9700

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