I think science too much, apparently.

  1. My friend's girlfriend asked us a question from one of her home ec classes to stump us. I'm sure you've all heard it before.

    "What will give you a worse cut, a dull knife, or a sharp knife."

    My response: "a sharp knife, because obviously, its narrower edge allows it to split materials more efficiently (it can be thought of as a wedge..)"

    She responds, proudly: "Nope! With a dull knife you aren't paying attention because you think that since it's dull it won't cut you, so you're more likely to mess up and cut yourself."

    A friend responds: "Yeah, you just aren't thinking deep enough into it."

    I explain to them: "No, I think it's more of the fact that I don't see how it make sense to make a judgment call on the person handling two materials when trying to compare two materials."

    I was thinking science too much, they said. And perhaps they are right. When I hear this question asked I want an experiment set up where there are no mysterious variables like the snotty disposition of the person while using the dull knife. I want the same event repeated with the dull and sharp knives.

    It's like saying "which is more malleable, gold or nickel?" Nickel, because you assume gold is more malleable so you hit it harder, which breaks it. Therefore nickel is more malleable than gold.
     
  2. jcsd
  3. You're right, they're wrong.
     
  4. The question is not worded well. "Worse" can mean a lot of different things. Cuts with sharp knives tend to be cleaner, but can possibly be deeper. Dull knives damage more tissue (and can complicate the matter with nasty side effects like tearing or shredding flesh) and you also have less control over them, giving them a strong argument for being "worse."
     
  5. See, that's the type of reasoning I can get behind. If dull knives give "worse" cuts, the person wielding the knive's attitude toward their task isn't a valid reason behind such a claim. That is interference with the experiment.

    I don't know much about knives and if someone would explain to me why I was wrong the way you did I would accept that. The reasons given just urked me.
     
  6. Dembadon

    Dembadon 678
    Gold Member

    The question is ambiguous. In order to have a meaningful discussion about it, there would need to be an agreement on a number of variables (type of blade used, pressure applied, duration of cutting, motion used to cut, etc).

    That doesn't follow. The question wasn't, "Are you more likely to cut yourself with..."
     
  7. i don't accept their explanation. a dull knife requires more force to make a cut. so it's more likely you apply too much force, slip, and lose control of your tool.
     
  8. Thats exactly what I thought when reading the OP.
     
  9. russ_watters

    Staff: Mentor

    The question is not ambiguously worded. All else being equal, a sharp knife will cut you worse. Period. They didn't answer the question asked, they answered a different one - a question such as "which is more likely to cut you?"
     
  10. Evo

    Staff: Mentor

    Your friend's girlfriend got it wrong. She has poor comprehension skills.

    The saying is that you are more likley to cut yourself with a dull knife because you need to apply more pressure and the knife is more likely to slip and cut you.

    His girlfriend = Fail
     
  11. No, other people don't think science enough.
     
  12. Pardon my ignorance, but what is a home ec class? Cooking?
     
  13. russ_watters

    Staff: Mentor

  14. Ah! Thanks!

    Wow! That is actually quite interesting. I wonder if my school offers that? Thanks for the link!
     
  15. Dembadon

    Dembadon 678
    Gold Member

    "Ceteris paribus" wasn't in the question, so, to me, there is ambiguity. Also, "worse" can be subjective. I'd ask for some criteria and rules for testing (amount of blood, depth of cut, how long it takes to heal, etc.) to avoid any shenanigans.
     
  16. I agree with your friend's girlfriend, but for different reasons. Sharp knife would make a clean cut where as a dull knife would tear the skin and mangle the nerves. I think this is why papercuts hurt much more than a knife cut.

    If you don't believe me, have you ever drop a glass object and cut yourself? I tend not to feel glass cuts because the glass is so sharp, making a smooth incision into my skin. Also, a dull knife blade is likely to make a wider cut than a sharp knife, contacting more nerves. Basically, if you had to have a limb amputated, which would you choose: sharp knife or dull knife? Simple choice, right? The dull knife will damage your nerves, which is why surgeons use sharp knives.
     
  17. Pengwuino

    Pengwuino 7,118
    Gold Member

    As much as this can become a, pardon the pun, an issue of splitting hairs, there is a simple argument for why at least they're wrong. They didn't answer the question. They answered a different one. So as Evo said, their comprehension skills are sub-bar to say the least.

    It's equivalent to saying "Which costs more, a soda in sweden or a soda in south africa" and answering "In south africa because you're more likely to be attacked by muggers who proceed to shoot you". If that sounds retarded, there is good reason.
     
  18. Evo

    Staff: Mentor

    AAarrgh, she had it wrong, read my post! This is a very well known question in cooking. She got it backwards. FAIL
     
  19. Very authoritarian. Yet you aren't answering the same question.

    = Likelihood of cut.
    Which is what the gf messed up.

    =Severity of cut.



    I'd rather have a sharp knife for three reasons.
    1. They are easier to control.
    2. If you do cut yourself, a clean cut is generally easier to sort out. (even if you chop your finger off a clean cut will be easy to sew it back on).
    3. Dull knives piss me off so much.
     
  20. Right. Worse to my mind actually means less efficient, i.e. not a clean cut. I'd rather cut my cheese or vegetables with a sharp knife, not a dull one. A dull one would be "worse." Poorly worded question.

    But when your GF asks you a question like that, it is more a matter of psychology and diplomacy than of science to find the proper response. It's not about too little or too much science. I have read that the difference between a nerd and a geek is that a geek is smart but doesn't lack social skills. It's ok to be geeky.

    -DaveKA
     
  21. That sounds good in theory, but I don't think it's true. First of all, dull isn't defined. I've never cut myself with a dull knife, it's always been a sharp knife. But the reason I say I've never cut myself with a dull knife is because if I cut myself with it, then I'm unlikely to conclude that it's dull. I may have cut myself with a dull knife, but then again, if it's dull, how did it cut me? Apparently it's not dull enough not to cut me.
    Spoons are dull. I've never cut myself on one of those.
     
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