I must have been asleep in physics when we did torque (well it was a while ago, before I discovered beer) and am re-visiting the subject afresh. I am trying to choose a motor to lift a pop-hole door to a hen house. The motors I'm looking at have a torque rating from 400 to 1000 gf.cm, which I gather to be gram force cm. I'm just not to sure on the significance. My plan is to have a string attached to the door and a motor to wind it up about a foot. If the door weighs 500g, what motor should I go for?