Textbook Question 4A.3

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Ellen Amico 2L
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Joined: Thu Sep 19, 2019 12:16 am

Textbook Question 4A.3

Postby Ellen Amico 2L » Fri Jan 31, 2020 4:37 pm

The question says: "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?"

I'm mainly confused on how to do part c, because usually change in internal energy is = q−pΔV, but there's no mention of heat anywhere in the problem so I'm not sure how to calculate ΔU.

AlyssaYeh_1B
Posts: 100
Joined: Sat Aug 17, 2019 12:16 am

Re: Textbook Question 4A.3

Postby AlyssaYeh_1B » Fri Jan 31, 2020 8:47 pm

The question is assuming that only work is done, so heat is not a component of the change of the internal energy. In this case, delta U = w. Your answer for (c) should therefore be the same as (a)


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