Hello, I am having trouble understanding an example shown on youtube regarding pulleys. http://www.youtube.com/watch?v=vSsK7Rfa3yA#t=3m0s In the example in the video above (I linked to the time when the example starts), the narrator uses an example where he pulls a rope with 5 Newtons for 2 meters, making a weight of 10 Newtons raise 1 meter. He is demonstrating mechanical advantage. http://en.wikipedia.org/wiki/File:Pulley1a.svg That is the basic setup, with W = 10N However my understanding is that if 5 Newtons is applied to the end of that rope, the system will be in equilibrium. In the picture above, the implication seems to be that if the end of the rope has W/2 applied to it, there is no movement. So how can the person in the video be pulling on that rope with a force of 5 Newtons and make the rope move at all? Thanks.