![]() This happens to me frequently when doing physics. ![]() I am quite literally stuck in my mindset. I don't know how to imagine this situation any other way. Because the masses are balanced, the block will remain at the same height but be moved along the length of the string. You can hold the block with the hole in place relative to the ground and pull a length L through the hole. The person climbing would be equivalent to a block with a hole in it which is small enough to hang on the rope through friction but loose enough to pull a length of rope through it. However the masses remain at the ends of the rope which are fixed along its length. What does "force balance" mean? Why would the person rise relative to the ground if the rope is moving down as they are pulling it? I have watched videos of atwood machines and when one side goes up a distance the other side goes down the same distance. How is that length #L# divided between the distance the person rises relative to the ground, and the distance the block rises relative to the ground? So, as in the picture below, you pull the rope down to lift the weight up. One wheel If you have a single wheel and a rope, a pulley helps you reverse the direction of your lifting force. Consider: in terms of distance along the rope, the block is a length #L# closer to the person if a length #L# of rope passes through the person's hands. How pulleys work The more wheels you have, and the more times you loop the rope around them, the more you can lift. The key to the problem is not acceleration relative to the ground. The correct answer is stated as Ya = y1+d/2 and Yb = y2 - d/2. The final y coordinates of the masses are Ya = y1 + d and Yb = y2 - d. Therefore, when P moves distance d, so should Q and R since this is just equivalent to sliding the rope along a numberline (also drawn). As I said before, the relative distance between these points are constant. I have marked points P, Q, and R in the attached diagram. because the rope does not stretch, the distance between points on the rope does not change(this is why the acceleration is the same for both sides of the atwood machine). There are two masses A and B at heights y1 and y2 from the 0 point at the center of the pulley. Lets just start with a simple atwood machine with a massless rope and frictionless pulley. Hi everybody, I've really been struggling with this basic idea, I have drawn it out about half a dozen times, watched numerous videos, read descriptions, played with applets but I still can't see it.
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