Eli5: why are the tips of scissors worse at cutting than the base?
In: 38
In addition to the other comments, since the base is closer to the hinge, more force is applied there thru leverage than further down the blade.
They aren’t, necessarily. Scissors are not particularly sharp – they do not cut like a knife.
Scissors cut by having the blades slide past one another, shearing the material. It only works if there’s no room between the blades for the material to slip through.
The blades are a little bit bendy, though, and the hinge isn’t perfect. Out by the tips, there is usually some room for the material to squeeze between the blades and thus escape being cut.
They’re not inherently worse but the base is closer to your hand which affords you more control. Also we’re typically cutting paper which wobbles and flexes around alot but when it’s at the base a fair portion of it is resting between the blades and kept straight which makes cutting much easier. The tips are also more likely to ber worn out from use by trying to cut harder materials since if the base can’t cut something it slides all the way to the top where it sticks. Also from just handling the scissors or dropping them the tips are more exposed to damage.
They’re not inherently worse but the base is closer to your hand which affords you more control. Also we’re typically cutting paper which wobbles and flexes around alot but when it’s at the base a fair portion of it is resting between the blades and kept straight which makes cutting much easier. The tips are also more likely to ber worn out from use by trying to cut harder materials since if the base can’t cut something it slides all the way to the top where it sticks. Also from just handling the scissors or dropping them the tips are more exposed to damage.
They’re not inherently worse but the base is closer to your hand which affords you more control. Also we’re typically cutting paper which wobbles and flexes around alot but when it’s at the base a fair portion of it is resting between the blades and kept straight which makes cutting much easier. The tips are also more likely to ber worn out from use by trying to cut harder materials since if the base can’t cut something it slides all the way to the top where it sticks. Also from just handling the scissors or dropping them the tips are more exposed to damage.
Near the base the blades will be extremely close and well fitted to each other. As you move down the scissor toward the tip, you’re further from the bolt holding them together, and there’s more likely to be a little bit of separation between the blades.
When the blades are very close you’re applying force to a relatively small number of strands of cellulose. If the blades have separation, the paper can twist and you end up applying tensile force rather than shear. In doing so you significantly increase the number of strands you’re applying force to at the same time.
In theory you could manipulate a pair of scissors to be poorly fitter near the base and very well fitted toward the top and you should notice the opposite. You’ll notice the same if you simply grab a sheet between the thumb and index finger of each hand with the fingers very close together in attempt to tear, vs fingers far apart to pull.
The fewer strands you’re applying force to simultaneously, the better you’ll be able to break/separate the strands (cut).
Near the base the blades will be extremely close and well fitted to each other. As you move down the scissor toward the tip, you’re further from the bolt holding them together, and there’s more likely to be a little bit of separation between the blades.
When the blades are very close you’re applying force to a relatively small number of strands of cellulose. If the blades have separation, the paper can twist and you end up applying tensile force rather than shear. In doing so you significantly increase the number of strands you’re applying force to at the same time.
In theory you could manipulate a pair of scissors to be poorly fitter near the base and very well fitted toward the top and you should notice the opposite. You’ll notice the same if you simply grab a sheet between the thumb and index finger of each hand with the fingers very close together in attempt to tear, vs fingers far apart to pull.
The fewer strands you’re applying force to simultaneously, the better you’ll be able to break/separate the strands (cut).
Near the base the blades will be extremely close and well fitted to each other. As you move down the scissor toward the tip, you’re further from the bolt holding them together, and there’s more likely to be a little bit of separation between the blades.
When the blades are very close you’re applying force to a relatively small number of strands of cellulose. If the blades have separation, the paper can twist and you end up applying tensile force rather than shear. In doing so you significantly increase the number of strands you’re applying force to at the same time.
In theory you could manipulate a pair of scissors to be poorly fitter near the base and very well fitted toward the top and you should notice the opposite. You’ll notice the same if you simply grab a sheet between the thumb and index finger of each hand with the fingers very close together in attempt to tear, vs fingers far apart to pull.
The fewer strands you’re applying force to simultaneously, the better you’ll be able to break/separate the strands (cut).
The left/right handedness also applies to what people are talking about.
Specifically scissors are designed so that the piece your thumb goes through is the inner blade, and your fingers the outer one. This way the natural way your hand pulls (thumb in, fingers slightly out) will force the blades together, helping cut.
But, if you are left handed and use right-handed scissors, now if you run into a tough material/cut, the natural pressure of your thumb pulling inwards is bad, as it opens the gap between the blades.
The amount of energy dissipated by the scissors is directly proportional to the length of the line cut through the material. Meaning the power (Joules per second) is proportional to the speed of the intersection point between the blades as the angle between the scissors is changed.
Using the angular separation of the blades as an independent variable, the power is proportional to its cotangent. This is a value that is close to 0 when the blades are at a right angle and hardly cutting anything, and approaches infinity when the blades approach being parallel and the intersection point travels infinitely fast. So when the angle is close to zero and the intersection point is near the tip, you have to squeeze harder to keep the angle changing at a constant rate.
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