5. Point Q is 3m above and 4m to the North of Point P. Ignoring friction how much energy does it take to move a 5kg sack of potatoes from point P to point Q? These are multiple choice questions of the exam, so in the mark scheme it only says: A, B .... The question paper can be found here:http://www.physics.ox.ac.uk/olympiad/Downloads/PastPapers/BPhO_PC_2004_QP.pdf The markscheme can be found here:http://www.physics.ox.ac.uk/olympiad/Downloads/PastPapers/BPhO_PC_2004_MS.pdf I am looking for an explanation as to why I am wrong My current working: We can use the Pythogorean Theorem , to determine that the box has to be moved a diagonal distance of 5m. (Right/ Wrong and why?) 5kg can give an approximate value of about 50N (e.g. gravitaional field about 10 ms^2)(Right/ Wrong and why?) Finally we can use the equation W = fxd = 50N x 5m = 250J(Right/ Wrong and why?) But in the marscheme it says the solution is C, namely 150J... Why?