havent you got the equation for that? http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/forces/workpowerrev1.shtml
http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/forces/workpowerrev1.shtml
I'm doing this at a degree level so those equations cant be used they are too basic, thanks though