for my homework : the question was explain how a skyscraper crane uses physics moments but no where can i find out the answer and dont want a detention ekkk x
OK... So what has your homework actually asked you to explain? Can you post the question...? There are moment forces going through a crane, is the aim of the homework simply for you to explain what a moment force is using a specific example ? A crane can be thought of in simple terms as a cantilever, ie one supported end and one free end, the lever arm force as it is sometimes referred to in schools is actually the moment force i.e. the moment for a crane with a boom L=40m long lifting a load of P=10kN would beP*L = 10*40 = 400 kNm, this is ignoring the self weight of the boom, if the boom weighed W=1.5kN/m (thats per meter, not to be confused with kNm which is kilo newton meters) then the moment generated by the self weight would be (WL^2)/2 = (1.5*40^2)/2 = 1200kNm so the total moment would be 1600kNm, so just remember for a point load the moment is force * distance from support ( in cantilevers) hope this helps... :)
