the incredible lifting machine heat loss??

[tubworld]

While stumbling upon this website on the Incredible lifting machine,

http://tigre.ucr.edu/dipen/phy11/heat.htm
I was wondering what could be some of the reasons why the work down calculated as in mgh does not equal to the work done under the pv graph?

I thought it should be the same? if not, that means there is heat loss by via what means???

[Andrew Mason]

While stumbling upon this website on the Incredible lifting machine,
http://tigre.ucr.edu/dipen/phy11/heat.htm
I was wondering what could be some of the reasons why the work down calculated as in mgh does not equal to the work done under the pv graph?
I thought it should be the same? if not, that means there is heat loss by via what means???What suggests to you that the increase in potential mechanical energy of the system is not equal to \int Pdv?

AM