Engineering question on energy/work (1 Viewer)

[iatethesun]

Hey guys, I have question which I am not sure on.

During the operation of a windlass, 30 metres of chain are to be wound on to the drum. Determine the work done on the chain if the chain has a mass of 0.5kg/m.
What I did was use the potential energy formula: Mgh -> 15 x 9.8 x 30 = 4410 J. The answer says it is 2205 Nm.
So could anyone tell me why I need to divide by 2 or what I am doing wrong and why the answer is in Nm please? and thank you!

 

[D94]

It's in Nm (Newton Metres) because when you use mgh, mg is a Force which is measured in Newtons, and h is the distance measured in Metres, hence Nm.

As to the question itself, I believe you need to know the mechanics of a windlass. It's a pulley system, so the work done is half the work needed to lift it from point A (ground) to point B (vertically upwards).

http://en.wikipedia.org/wiki/Windlass