Mechanics 2 Energy, Work and Power - HELP ME!

Hi guys,


I'm really quite confused at this question I've just done on Jan 2013 Mechanics paper.


The paper is available to download here: http://tinyurl.com/m93d388.
And the question I don't understand is: 2ii.


What I don't understand is why you take away the total work done away from the GPE?


If someone could shine some light on this for me I'd highly appreciate it!

Hi guys,


I'm really quite confused at this question I've just done on Jan 2013 Mechanics paper.


The paper is available to download here: http://www.ocr.org.uk/Images/144674-question-paper-unit-4762-01-mechanics-2.pdf
And the question I don't understand is: 2ii. Which I've used Increase in KE (0.5*80*(vsqrd-4)) = Mgh (80*9.8*12sin(4))

What I don't understand is why you take away the total work done away from the GPE? Making it:

40vsqrd - 160 = 656 - 455.


Why is the total work done taken away from the GPE?