How could a lever be used to lift the object

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A lever can be used to lift an object that is three times heavier by strategically placing the fulcrum. The textbook suggests two configurations: one where the fulcrum is one-quarter of the way across the lever and another where it is at the end with the object positioned one-third of the way across. This latter setup results in a 3:1 ratio of lever arms, requiring only one-third of the original force to lift the object. The discussion highlights the importance of understanding lever classes, as the direction of applied force can significantly affect lifting capability. Properly visualizing these configurations is crucial for grasping the mechanics of levers.
AlexandraBoiko
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Hello everyone!

I'm new here and I have never been too good at physics, but now I've been trying to revise for the MCAT and I have stumbled across this question in "Kaplan MCAT Physics and Math Review":
If you have and object three times as heavy as you can lift, how could a lever be used to lift the object? Where would the fulcrum need to be placed?

I know the answer is obvious, and I have drawn the picture that I have attached to this post (where you place the fulcrum one quater of the way across the lever), but the textbook says that, alternatively, the fulcrum could be placed at the end with the object one-third of the way across the lever. It says that this would again result in a 3:1 ration of lever arms, meaning that only one-third of the original force is necessary, but I don't understand - how can there be a 3:1 when the object is placed one-third of the way across the lever?
Could anybody please draw the alternative position of the fulcrum described in the textbook? I just can't picture it:(
 
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Sorry! I've just realized it's the wrong thread...
 
AlexandraBoiko said:
...the fulcrum could be placed at the end with the object one-third of the way across the lever... I just can't picture it:(
See class 2 here:
https://en.wikipedia.org/wiki/Lever#Classes_of_levers
 
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Thank you very much!
 
Note the different directions of the forces for the three 'classes'. The choice could make a big difference to the choice in a practical situation. When the applied force would be downwards, it could be your weight and not your strength that would limit the maximum load. A weak, heavy person could find Class 1 very useful but an immensely strong lightweight would just manage to push himself up off the ground.
 
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I see, thank you!:smile:
 
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