3 ms·

I kinda feel for this guy. Sometimes I feel like we're under the tyrannical yoke of algorithms. Not modern algorithms that display ads, but like super-simple

I kinda feel for this guy. Sometimes I feel like we're under the tyrannical yoke of algorithms. Not modern algorithms that display ads, but like super-simple ones. E.g. consider a basic rope pulley or some simple gears. Rig some of those up and suddenly it becomes easier to move a weight. Why? Because Work = Force x Distance and you're increasing the distance for the same amount of work so force goes down. .... okay, I understand the maths, but why does turning a small gear more quickly than the big gear make it easier? Forget the equation that models this for a moment - intuitively my brain does not grok why it gets easier to move something by pulling a bit more rope than usual. Most explanations from the teachers at school was something like "Because physics", but I am still not comfortable understanding intuitively what precisely is going on with the physical forces without just shrugging and and going back to the mathematical model W=F*D ruling our lives without really understanding why. ...so I guess I just have to see the universe in numbers like this guy, and so am also a genius ahead of my time?

wizzwizz4 6y ago
Your muscles work by contracting little strings, which transfers energy. They've got a limit for how much energy per distance-contracted (aka force) they can apply. Levers and pulleys are simple devices that move one thing a certain distance while another thing moves a different distance, but transfer the energy while doing so. They let you transfer the same amount of energy over a larger distance, so there's less energy-per-distance (force), so your muscles can cope with it. (They have to do more contraction-expansion cycles, but it's easier because there's less energy going into each of them.)
imtringued 6y ago
>intuitively my brain does not grok why it gets easier to move something by pulling a bit more rope than usual Warning: This is probably wrong because I am conjuring this from my mind without looking up any resources. You have rope. The rope can carry 50lb. You want to lift something that weighs 100kg. You cut the rope in half and attach two ropes to the stone and the ceiling. Now you got a 100lb weight attached on two 50lb ropes. The cross section area of the rope is 1 square inch (random number). The rope happens to hold exactly 50lb per square inch. We write this down as 50 psi. But wait. Since we added two ropes we have increased the cross section thus we have 100lb hanging on 2 square inches of rope. We are still within 100lb/2i^2 = 50psi. What if we have 4 ropes? 100lb/4i^2 = 25psi and so on. The amount of force each rope applies on the stone is shrinking. Since 1 rope = 1 square inch we get 25 pounds of force on each rope. Now lets go back to pulleys. There is no meaningful difference between statically attaching rope (although one end has to be attached) and letting it hang off a pulley or letting an object hang off a pulley. The end result is that you have effectively attached the rope 3 times to the ceiling and what you are holding is only a faction of the cross section area that is actually holding up the stone. You have to pull more rope because there is 4 times as much rope and the wall is just holding the rope at a fixed point.

wizzwizz4 6y ago

Your muscles work by contracting little strings, which transfers energy. They've got a limit for how much energy per distance-contracted (aka force) they can apply. Levers and pulleys are simple devices that move one thing a certain distance while another thing moves a different distance, but transfer the energy while doing so. They let you transfer the same amount of energy over a larger distance, so there's less energy-per-distance (force), so your muscles can cope with it. (They have to do more contraction-expansion cycles, but it's easier because there's less energy going into each of them.)

imtringued 6y ago

>intuitively my brain does not grok why it gets easier to move something by pulling a bit more rope than usual Warning: This is probably wrong because I am conjuring this from my mind without looking up any resources. You have rope. The rope can carry 50lb. You want to lift something that weighs 100kg. You cut the rope in half and attach two ropes to the stone and the ceiling. Now you got a 100lb weight attached on two 50lb ropes. The cross section area of the rope is 1 square inch (random number). The rope happens to hold exactly 50lb per square inch. We write this down as 50 psi. But wait. Since we added two ropes we have increased the cross section thus we have 100lb hanging on 2 square inches of rope. We are still within 100lb/2i^2 = 50psi. What if we have 4 ropes? 100lb/4i^2 = 25psi and so on. The amount of force each rope applies on the stone is shrinking. Since 1 rope = 1 square inch we get 25 pounds of force on each rope. Now lets go back to pulleys. There is no meaningful difference between statically attaching rope (although one end has to be attached) and letting it hang off a pulley or letting an object hang off a pulley. The end result is that you have effectively attached the rope 3 times to the ceiling and what you are holding is only a faction of the cross section area that is actually holding up the stone. You have to pull more rope because there is 4 times as much rope and the wall is just holding the rope at a fixed point.