## calculating volume change

205192823
Posts: 100
Joined: Wed Sep 18, 2019 12:19 am

### calculating volume change

The inner diameter of the pump is 3.0 cm and the pump is depressed 20. cm with a pressure of 2.00 atm. This is a question where I would have to use the expansion work equation but in this situation for the change in volume how would i solve it? Question: 4A #3

Katie Kyan 2K
Posts: 106
Joined: Fri Aug 09, 2019 12:16 am
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### Re: calculating volume change

You can use the equation for the volume of a cylinder which is pi(r^2)h. Since you know the diameter of the pump, you can find its radius and the delta h would be 20. cm because this is how far the pump is depressed.

205192823
Posts: 100
Joined: Wed Sep 18, 2019 12:19 am

### Re: calculating volume change

I figured out how to solve it by using the volume formula for the cylindrical shape pump and found the change volume equation (delta V= pie*r^2*delta h) and got delta V= pie(1.5 cm)^2(-20.0 cm)= 141.37 cm^3 and used 0.001 L=1 cm^3 to convert and got -0.1437 L. Then plugged the delta V into work=-Pex*delta V and got w=-(2.00 atm)( -0.14137 L)= 0.283 atm*L. I know the work is in Joules so I'm confused how 0.283 atm*L was converted into 2.8 J.

205192823
Posts: 100
Joined: Wed Sep 18, 2019 12:19 am

### Re: calculating volume change

Katie Kyan 2K wrote:You can use the equation for the volume of a cylinder which is pi(r^2)h. Since you know the diameter of the pump, you can find its radius and the delta h would be 20. cm because this is how far the pump is depressed.

Thank you!

Mai V 4L
Posts: 111
Joined: Fri Sep 28, 2018 12:23 am

### Re: calculating volume change

Dooes anyone have a video they think is a good reference for this topic?