Mechanical Engineering: Particle Equilibrium (13 of 19) Pulleys and Mechanical Advantage

welcome to electron line and here's our third set of police this is a little bit more complicated at least a little bit more complicated looking the approach is exactly the same what we're trying to do here is find the amount of force required to hold up the weight or to pull the weight up now of course if you pull the weight up at a constant speed the amount of force required is exactly the same as holding it in place now let me see here's my black pen alright so we start over here let's draw a Freebody diagram on this portion of the first pulley set and you can see that there's a hundred Newton's of force pulling down two ropes pulling up so those two must add up to 100 pounds so these are the two ropes that are upholding the weight and since it's the same rope going around the same pulley that means the rules of pulleys that the tension here must be equal to tension there they must add up to 100 Newtons so therefore it is 15 Newtons on this side and 15 Newtons on this side now if we draw a second Freebody diagram around this part of the pulley set right here notice that the force pulling down here which is 50 Newtons must equal the sum of the two forces up there pulling up and since it's the same rope going around this pulley the force here the tension here must be the same as this tension there they must add up to 50 Newtons which means we're going to have 25 Newtons on this rope and 25 Newtons on that rope and of course since this rope goes around this pulley the force here the tension here must be equal to the tension there this must also be 25 Newtons which means the force required to hold up the weight here the 100 do to wait here is 25 Newtons or does also the amount of force to pull up this weight right here at a constant speed upward again since the for the one mechanical advantage to lift us up 1 meter you'll have to pull down on this 4 meters ok looking at the second set assuming that this is a bracket right here suspending the 100 Newton weight on those two pulleys we can assume that'll be 15 Newton's of force on each one so we can say 15 Newtons over here and 50 Newtons over there now if you draw a Freebody diagram you can do draw one over here or you can draw one over here you get the exact same result notice that in each case the 50 Newton's pulling down is being upheld by the two strings over here and the two strings over there which means that those two together must add up to 20 I must add up to 50 Newtons and these two must add up to 50 Newtons and since both of these go around the same pulley that means a tangent here mystical detention there and both of those go around the same puller that means attention here mystical detention there that means all of them will be equal to 25 Newtons of 25 Newtons for this 125 Newtons for that 125 Newtons for this one and 25 Newtons for this one it also makes sense because just as the tensions on both sides here must be the same the tensions on both sides there must be the same which also means that the tension over here must be the same on both sides which means we have 25 Newtons over here which means we need a force of 25 Newton to hold up this weight or to pull it upwards at a constant speed again a four-to-one mechanical advantage going to the third system right here again we can draw Freebody diagram so you can see here that this way of 100 Newtons is being upheld by those three strings over here over there and over there notice that the tension on this string must be the same on both sides because it is the same string going around this pulley and attention here must equal to the tension there because that string is going around the pulley over here which means all the tensions are equal to each other they all add up to 100 Newtons which means 33 Newtons for each one so 33 Newtons for this 33 Newtons for this one and 33 Newtons for this one and since this string goes around this pulley the tangent here must equal the tension there 33 Newtons on this side which means the force required to hold this up against gravity or to pull it up at a constant speed is 33 Newtons a three to one advantage one more thing now let's try to find the force that pulls down from the ceiling on these three strings well if this is 15 Newtons here that means we need a 15 Newton's force over there over here we need a 25 Newton force and over here this is 25 Newtons and 25 Newtons together that's 50 Newton's so we need a 50 Newton force over there a total of 125 Newtons to hold up the 100 Newton weight coming over here you can see that these two together add up to 50 Newtons and that is being held up by the single string so that's 50 Newtons over here at the same situation over here 50 Newtons and here we have a 25 Newton force so the total force on the ceiling is 112 at 25 Newtons to uphold 100 Newton weight finally coming over here you can see we have 33 Newtons and 33 Newtons together add up to 66 so let's run it off to 67 because this is really 33 in the third Newton's so 67 Newtons and here we have 33 Newtons and 33 Newtons again 67 Newtons so you can see that you have a force of 133 Newton's pulling down from the ceiling to uphold a weight of 100 Newtons here and that's how we figure that out

Channel: Michel van Biezen

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Keywords: ilectureonline, ilectureonline.com, Mike, Mike van Biezen, van Biezen, ilecture, ilecture online, Mechanical Engineering, Particle Equilibrium, Mechanics (Field Of Study), Force (Dimension), Component, Zero, Equal, Reactionary Force, Static, Sum of the Forces = 0, Cable Under Tension, Resultant Force, Pulley (Product Category), Mechanical Advantage, More Complicated

Id: QVbuGPEdNEo

Length: 5min 29sec (329 seconds)

Published: Tue Jun 23 2015