Learn about Mechanical Advantage - part 2 Video

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Learn about Mechanical Advantage - part 2

Learn about Mechanical Advantage - part 2 Welcome back. When I left off, I was hurrying a little bit but we’d hopefully come to the conclusion that if I have a simple lever like I have here and I know the distance is from where I am applying the force to the fulcrum, to the pivot and I know the distance from the pivot to where the machine is essentially applying the force or the machine being the lever in this situation. I know the relationship between the two forces I am applying. The input force, so actually I should not call this force too. I should call this input force. Well anyway, the input force times the distance from the input force to the fulcrum is equal to the output force times the distance from the output force to the fulcrum. And that all fell out of what we did in the last video of the conservation of energy and that the work in has to equal to work out. And all work is a transfer of energy so the transfer of energy in has to be the transfer of energy out assuming we have no friction and none of the energy is lost. And how is this useful? Well, I could say, we can do a bunch of problems with this. Let’s say that I have a 100 N object right here. And let’s say that I know no matter what I do my maximum strength that I could push—well let me draw this a little different. Let’s say it is like this because my goal is to lift a 100 N object. So, the 100 N objects is right here. That’s a 100 N. And let’s say I know that the maximum downward force that I am capable of applying is only 10N, right? So I want my force to be multiplied by 10 to lift this force. So let’s figure out what would happen. My input force is 10 and I want to figure out the distance of—to the—so let’s say my input force is 10 and let’s call this the input distance. And I want the output force to be 100, right? And let’s call this the output distance, right. So, if I have a fulcrum here, this is the input distance and this is the output distance. So let me switch colors. This is going monotonous. This is the output distance from here to here. And let’s figure out what the ratio has to be for the input, output—for the ratio of the input distance to the output distance. Well,. If we just divide both sides by 10, we get distance input. It has to be 10 × the distance output, right? It is 100 ÷ 10. So if the distance from the fulcrum to the weight is—I don’t know—5 m. Then the distance from where I am applying the force to the fulcrum has to be 10 times that. It has to be 50m. So, no matter what the ratio of this length to this length has to be 10. And now, what would happen? If I design this machine in this way, I will be able to apply 10 N here which is my maximum strength. It is 10 N downwards. And I will lift a 100 N object. And that was the trade off though. You know nothing just pops out of thin air. The trade off is, is that I am going to have to push down from a much longer distance for actually 10 times the distance as this object is going to move up. And once again, I know that because the work in has to equal to work out. I can’t—through some magical machine and if you were to be able to invent one, you should not watch this video and you should go build it in, become a trillionaire but a machine can never generate work out of thin air or can never generate energy out of thin air that energy has to come from some place. Most machines actually will lose friction or whatever else but in this situation, if I am putting in 10 N of force times some distance, whatever that quantity is of work, the work can not change the total work. It can go down if there is some friction in the system. So let’s do another problem. And really, there are all kind of the same formula. And then I’ll move into a few other types of simple systems. And once again, just to—I should use the line tool and make this up on the fly. And you could always create problems where you could compound it further and etc. etc. using some of the other concepts we’ve learned. Well don’t worry about that right now. So let’s say that I have a—I am going to push up here. Oh no let’s me see what I’m going to do. I want to push down here with a force of—let’s say that this distance right here. Let’s say this distance is 35m. This distance is 5m. And let’s say I am going to push down with a force of 7 N. And what I want to figure out is how heavy of an object can I lift here? How heavy of an object. Well, all we have to do is use the same formula that the moments—and I know I use that word once before so you might not know what it is but the moments on both side of the fulcrum have to be the same where the input moment has to be the output moment. So what’s the moment again? Well the moment is just the force times the distance from the force to the fulcrum. So the input moment is 7 N times 35 m. And realize that that is not work because the distance as force is traveling is not 35m.The distance as force is traveling is something like here. But this 35 m is going to be proportional to the distance as this is traveling when you compare it to this other side. So this quantity, 7N × 35m is the moment and that is going to be equal to the moment on this side― the output moment. So that is equal to 5m × the force that I am lifting or the lifting force of the machine—times, let’s say the force out. so we can figure out the force out by just dividing both sides by five. So let’s see. 35 ÷ 5 is 7. So we get 7 × 7 equals a force out or 49 N. And you could see that because you can see that the length of this side of the lever is 7 times the length of this side of the lever. So, when you input a force of 7, you output a force of 7 times that and of course, in order to move the block 1m up in this direction, you’re going to have to push down for 7m. And that’s where we know that the work—the input work is equal to the output work. Well anyway, hopefully I didn’t confuse you but—and you have a reasonable sense of how lever work. In the next couple of videos, I’ll introduce you to other machines; simple machines like wedge. I’ve always had trouble calling a wedge machine but it is one and the pulleys. I’ll see you in the next videos.

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Learn about Mechanical Advantage - part 2

Welcome back. When I left off, I was hurrying a little bit but we’d hopefully come to the conclusion that if I have a simple lever like I have here and I know the distance is from where I am applying the force to the fulcrum, to the pivot and I know the distance from the pivot to where the machine is essentially applying the force or the machine being the lever in this situation. I know the relationship between the two forces I am applying.

The input force, so actually I should not call this force too. I should call this input force. Well anyway, the input force times the distance from the input force to the fulcrum is equal to the output force times the distance from the output force to the fulcrum. And that all fell out of what we did in the last video of the conservation of energy and that the work in has to equal to work out. And all work is a transfer of energy so the transfer of energy in has to be the transfer of energy out assuming we have no friction and none of the energy is lost.

And how is this useful? Well, I could say, we can do a bunch of problems with this. Let’s say that I have a 100 N object right here. And let’s say that I know no matter what I do my maximum strength that I could push—well let me draw this a little different. Let’s say it is like this because my goal is to lift a 100 N object. So, the 100 N objects is right here. That’s a 100 N.

And let’s say I know that the maximum downward force that I am capable of applying is only 10N, right? So I want my force to be multiplied by 10 to lift this force. So let’s figure out what would happen. My input force is 10 and I want to figure out the distance of—to the—so let’s say my input force is 10 and let’s call this the input distance. And I want the output force to be 100, right? And let’s call this the output distance, right. So, if I have a fulcrum here, this is the input distance and this is the output distance. So let me switch colors. This is going monotonous.

This is the output distance from here to here. And let’s figure out what the ratio has to be for the input, output—for the ratio of the input distance to the output distance. Well,. If we just divide both sides by 10, we get distance input. It has to be 10 × the distance output, right? It is 100 ÷ 10.

So if the distance from the fulcrum to the weight is—I don’t know—5 m. Then the distance from where I am applying the force to the fulcrum has to be 10 times that. It has to be 50m. So, no matter what the ratio of this length to this length has to be 10.

And now, what would happen? If I design this machine in this way, I will be able to apply 10 N here which is my maximum strength. It is 10 N downwards. And I will lift a 100 N object. And that was the trade off though. You know nothing just pops out of thin air. The trade off is, is that I am going to have to push down from a much longer distance for actually 10 times the distance as this object is going to move up.

And once again, I know that because the work in has to equal to work out. I can’t—through some magical machine and if you were to be able to invent one, you should not watch this video and you should go build it in, become a trillionaire but a machine can never generate work out of thin air or can never generate energy out of thin air that energy has to come from some place. Most machines actually will lose friction or whatever else but in this situation, if I am putting in 10 N of force times some distance, whatever that quantity is of work, the work can not change the total work. It can go down if there is some friction in the system.

So let’s do another problem. And really, there are all kind of the same formula. And then I’ll move into a few other types of simple systems. And once again, just to—I should use the line tool and make this up on the fly. And you could always create problems where you could compound it further and etc. etc. using some of the other concepts we’ve learned. Well don’t worry about that right now.

So let’s say that I have a—I am going to push up here. Oh no let’s me see what I’m going to do. I want to push down here with a force of—let’s say that this distance right here. Let’s say this distance is 35m. This distance is 5m. And let’s say I am going to push down with a force of 7 N. And what I want to figure out is how heavy of an object can I lift here? How heavy of an object.

Well, all we have to do is use the same formula that the moments—and I know I use that word once before so you might not know what it is but the moments on both side of the fulcrum have to be the same where the input moment has to be the output moment. So what’s the moment again? Well the moment is just the force times the distance from the force to the fulcrum. So the input moment is 7 N times 35 m.

And realize that that is not work because the distance as force is traveling is not 35m.The distance as force is traveling is something like here. But this 35 m is going to be proportional to the distance as this is traveling when you compare it to this other side.

So this quantity, 7N × 35m is the moment and that is going to be equal to the moment on this side― the output moment. So that is equal to 5m × the force that I am lifting or the lifting force of the machine—times, let’s say the force out. so we can figure out the force out by just dividing both sides by five. So let’s see. 35 ÷ 5 is 7. So we get 7 × 7 equals a force out or 49 N.

And you could see that because you can see that the length of this side of the lever is 7 times the length of this side of the lever. So, when you input a force of 7, you output a force of 7 times that and of course, in order to move the block 1m up in this direction, you’re going to have to push down for 7m. And that’s where we know that the work—the input work is equal to the output work. Well anyway, hopefully I didn’t confuse you but—and you have a reasonable sense of how lever work.

In the next couple of videos, I’ll introduce you to other machines; simple machines like wedge. I’ve always had trouble calling a wedge machine but it is one and the pulleys. I’ll see you in the next videos.

Transcription by: Scribe4you Transcription Services