• (cs) in reply to Anketam
    Anketam:
    Sam:
    For the benefit of the woefully ill-informed, here is the correct definition of weight, and some notes on buoyancy...

    Mass is an invariant quantity which measures the resistance of an object to having its velocity changed; the higher the mass, the lower the acceleration produced by a given force (Newton's Second Law; F = ma). The SI unit is the kilogram.

    Weight is defined as the gravitational force applied to an object by another. In general, this is given by F = GMm/r^2, where M and m are the masses of the two objects, r is the distance between their centres of mass, and G is the gravitational constant. For objects on or near the surface of the Earth, GM/r^2 is approximately constant, and we get F = mg, where g is ~9.81m s^-2. Since weight is a force, its SI unit is the newton.

    Objects in a fluid under the influence of gravity experience a buoyancy force, which is due to the pressure difference between the top and bottom of the object. For most objects in air, this is small and tends to be ignored, but if an object weighs less than an equivalent volume of the fluid it's in, the buoyancy force is greater than the weight force, and thus there is a net upwards force. Since helium has a lower density than air, you can construct a balloon containing helium which floats in air.

    Obviously given this, the buoyancy force is much greater in denser fluids such as water, which is why a ship or an iceberg float.

    This is also why if you put a hellium balloon in a vacuum it will no longer float since there is no upward force coming from the buoyancy. Lastly if there is a scale in that vacuum the balloon will actually register weight.
    Wrong. The helium balloon would pop from the pressure difference. The rubber might register on the scale if its sensative enough.

    Edit: Damn me and my forgetting to refresh the page before commenting.

  • (cs) in reply to Jay
    Jay:
    PiisAWheeL:
    Parliamentary Train:
    Weight =! Mass
    What language uses =! for not = to (As apposed to != like all the languages I've ever used).

    If weight =! Mass, then when Mass is true, weight will be set to false, and vice versa.

    The train just went by and you are still standing on the platform.

  • thatguy (unregistered) in reply to PiisAWheeL
    PiisAWheeL:
    Parliamentary Train:
    Weight =! Mass
    What language uses =! for not = to (As apposed to != like all the languages I've ever used).

    You've never used dyslexic ++C before?

  • iWantToKeepAnon (unregistered) in reply to my little phony
    my little phony:
    So if I bought a tank of helium, would they pay me to ship it?

    That's almost exactly the script from an old "Tipsy Turtle" cartoon on the old SNL. Nobody I know remembers it.

    His m.o. was to start a riot and then go home and get drunk. He went to a post office and tried to mail a helium balloon and when the postman weighed the package it floated and he demanded they pay HIM.

    http://www.youtube.com/watch?v=hQfcbXUpIns (not my video)

  • (cs) in reply to Jay
    Jay:
    Reverse Polish ... would that be "shilop"?
    No, it would be "hsiloP".
  • (cs)

    Forget using helium, use hydrogen instead. It's lighter!

    In fact, I think the trucking industry could save lots of money if they displaced all the air in trailers with hydrogen. Boom!

  • DMJ (unregistered) in reply to frits
    frits:
    Forget using helium, use hydrogen instead. It's lighter!

    In fact, I think the trucking industry could save lots of money if they displaced all the air in trailers with hydrogen. Boom!

    Hydrogen is also more readily available and cheaper. What could go wrong with that plan?

  • Zunesis: Nothing Less Than The Best (unregistered) in reply to DMJ
    DMJ:
    frits:
    Forget using helium, use hydrogen instead. It's lighter!

    In fact, I think the trucking industry could save lots of money if they displaced all the air in trailers with hydrogen. Boom!

    Hydrogen is also more readily available and cheaper. What could go wrong with that plan?

    Oh, the ingenuity!

    You guys are brilliant!

  • DocDiep (unregistered)

    These are actually Non-destructive testing abbreviations. No idea why they sent it to you if you don't work in the field. MT - Magnetic Particle Testing PT - Penetrant Testing UT - Ultrasonic Testing RT - Radiographic Testing ET - Eddy Current Testing VT - Visual Testing FI - ? TOFD = Time of Flight Diffraction

  • (cs) in reply to Zunesis: Nothing Less Than The Best
    Zunesis: Nothing Less Than The Best:
    DMJ:
    frits:
    Forget using helium, use hydrogen instead. It's lighter!

    In fact, I think the trucking industry could save lots of money if they displaced all the air in trailers with hydrogen. Boom!

    Hydrogen is also more readily available and cheaper. What could go wrong with that plan?

    Oh, the ingenuity!

    You guys are brilliant!

    It's not as if truckers smoke or anything, either!

    Wait, there is a really, REALLY big problem with this idea... Why aren't we filling the tires with hydrogen, too?

  • Steve (unregistered) in reply to PiisAWheeL
    PiisAWheeL:
    Parliamentary Train:
    Weight =! Mass
    What language uses =! for not = to (As apposed to != like all the languages I've ever used).

    Yoda++

  • Oinky (unregistered)

    The real WTF, by the way, is having a 3-month password change policy.

  • Brendan (unregistered) in reply to Sam
    Sam:
    Weight is defined as the gravitational force applied to an object by another. In general, this is given by F = GMm/r^2, where M and m are the masses of the two objects, r is the distance between their centres of mass, and G is the gravitational constant.

    That can't be right. Imagine a solid ball inside a hollow sphere, where the centre of mass for both objects is at the same point (r = 0). Do you expect infinite gravitational force?

  • Uncle Al (unregistered) in reply to PiisAWheeL
    PiisAWheeL:
    Parliamentary Train:
    Weight =! Mass
    What language uses =! for not = to (As apposed to != like all the languages I've ever used).

    Actually, a not-so-flippant "hmmm..."; do software developers working on a workstation localized for a right-to-left language (e.g. Hebrew, Arabic) use right-to-left scanning in writing code? I'm trying to twist my mind around writing C++ or SQL "backwards", but also trying to twist my mind being a native reader of a right-to-left language trying to write code left-to-right.

  • Jim (unregistered) in reply to Uncle Al
    Uncle Al:
    Not to derail the helium/bouyancy/weight conversation -- but it looks like all that's happening is that the shipping department is using kilos.
    I'm surprised noones mentioned that maybe Amazon's simply worked out that the couriers don't actually weigh the package, so they can saveyou some postage...

    Also, what's with all the Scientists hanign around with baseball bats? Shouldn't they be clubbing seals or something?

  • Sam (unregistered) in reply to Brendan
    Brendan:
    That can't be right. Imagine a solid ball inside a hollow sphere, where the centre of mass for both objects is at the same point (r = 0). Do you expect infinite gravitational force?
    Sorry, I should have clarified - the formula given applies to point masses. It also happens that, from outside a sphere or spherical shell, the sphere behaves like a point mass, and it's also a reasonable approximation for a small arbitrarily shaped object in the gravitational field of a much larger one.

    You're entirely correct that it doesn't work for an object inside a hollow object. In fact, an object inside a uniform spherical shell feels no gravitational force due to the shell - all directions exactly cancel each other out, no matter where inside the shell it is placed.

  • Nagesh (unregistered) in reply to Zunesis: Nothing Less Than The Best
    Zunesis: Nothing Less Than The Best:
    Nagesh:
    Here in Hyderabad, we are frequency getting 0 chanels. [image]
    Who's the chick in the skirt?
    That is not chicken! That is being untochable I pay to adjust satleite dish.
  • Bill (unregistered) in reply to Sam
    Sam:
    In fact, an object inside a uniform spherical shell feels no gravitational force due to the shell - all directions exactly cancel each other out, no matter where inside the shell it is placed.
    By "inside" I think you mean completely inside the space that is enclosed by the shell. If I were inside the shell itself that wouldn't work, right?

    Otherwise, we could consider the Earth a nearly-uniform spherical shell where the shell is really thick, reaching down to within an atom of the center. And as soon as I dig a ten foot hole into the ground, I'd be weightless.

  • Zunesis: Nothing Less Than The Best (unregistered) in reply to Nagesh
    Nagesh:
    Zunesis: Nothing Less Than The Best:
    Nagesh:
    Here in Hyderabad, we are frequency getting 0 chanels. [image]
    Who's the chick in the skirt?
    That is not chicken! That is being untochable I pay to adjust satleite dish.
    Are you putting it past me to fuck a chicken? I wouldn't...
  • Carl (unregistered) in reply to Ralph
    Ralph:
    Zunesis: Nothing Less Than The Best:
    Ralph:
    Zunesis: Nothing Less Than The Best:
    Nagesh:
    Here in Hyderabad, we are frequency getting 0 chanels. [image]
    Who's the topless chick in the skirt? Tantalizing how you can see the silouette of her legs and ass.
    FTFY
    Can't you see that cloth hanging down in front? It contains her tits, so no visible nips.

    (Off to search for porn of elderly women tripping on their own tits... or each other's [GETTING HARD!])

    Yeah, so your interpretation is she's wearing one of those evening gowns that's cut really really low in the back? OK, that could still be hot. I mean, it is not merely what a woman wears that makes her seductive, it is the manifest intent to be provocative and bare!

    Still, I was fantasizing that there would be naked boobies there somewhere, so thanks for taking that away from me.

    And, she's barefoot too!

    But be careful gentlemen. She might be under age. It looks like she's only about three feet tall.

  • (cs) in reply to Jay
    Jay:
    Hey, aren't the admins supposed to be anonymizing these posts? I really don't appreciate having my son's name, 3995599, posted on a public web site.

    Please attempt to show a little sensitivity. I had a son named 3995599 once, and let me assure you, it was no laughing matter.

  • (cs) in reply to Zunesis: Nothing Less Than The Best
    Zunesis: Nothing Less Than The Best:
    DMJ:
    frits:
    Forget using helium, use hydrogen instead. It's lighter!

    In fact, I think the trucking industry could save lots of money if they displaced all the air in trailers with hydrogen. Boom!

    Hydrogen is also more readily available and cheaper. What could go wrong with that plan?

    Oh, the ingenuity!

    You guys are brilliant!

    Methane is even more readily available and comes completely free, from all you fuckwits talking out of your arses.

  • Ben Jammin (unregistered) in reply to Hmmmm
    Hmmmm:
    Ben Jammin:
    Weight is actually the number on my bathroom scale.
    Again, no. ...
    Again, yes. I assure you when people ask you your weight, they have no concern of barometric pressures, distance from the mass you're being pulled by, nor which planet you're on. Also, when weight is measured, a significant portion of the time, it isn't measured within a vacuum. I'm also positive you're never been asked, "What is your apparent weight?" When someone want to know your weight, they want the number off the scale.
  • Zunesis: Nothing Less Than The Best (unregistered) in reply to Matt Westwood
    Matt Westwood:
    Zunesis: Nothing Less Than The Best:
    DMJ:
    frits:
    Forget using helium, use hydrogen instead. It's lighter!

    In fact, I think the trucking industry could save lots of money if they displaced all the air in trailers with hydrogen. Boom!

    Hydrogen is also more readily available and cheaper. What could go wrong with that plan?

    Oh, the ingenuity!

    You guys are brilliant!

    Methane is even more readily available and comes completely free, from all you fuckwits talking out of your arses.

    I guess you had to have been there.

  • (cs) in reply to Oinky
    Oinky:
    The real WTF, by the way, is having a 3-month password change policy.
    I used to work at a place that had a 1-month password change policy. The users ended up writing their passwords on the first card in their Rolodexes, and even the sysadmin started using the month and year as the password. (need true story meme pic)
  • Sam (unregistered) in reply to Bill
    Bill:
    By "inside" I think you mean completely inside the space that is enclosed by the shell. If I were inside the shell itself that wouldn't work, right?

    Otherwise, we could consider the Earth a nearly-uniform spherical shell where the shell is really thick, reaching down to within an atom of the center. And as soon as I dig a ten foot hole into the ground, I'd be weightless.

    That's correct, yes. The behaviour as you tunnel down inside the earth can be found by splitting the Earth into two components - the shell above you, from which you feel no gravitational force, and the sphere below you, from which you do. Assuming the Earth is uniform, the gravitational force you feel decreases linearly from its maximum value at the surface to zero at the centre.

  • Oinky (unregistered) in reply to PedanticCurmudgeon
    PedanticCurmudgeon:
    Oinky:
    The real WTF, by the way, is having a 3-month password change policy.
    I used to work at a place that had a 1-month password change policy. The users ended up writing their passwords on the first card in their Rolodexes, and even the sysadmin started using the month and year as the password.[image]

    (here, fixed that for you)

    Well, with a 3 month password change policy, the sysadmins would use the QUARTER and year as the password. Much less predictable ! :-D

  • Hmmmm (unregistered) in reply to Ben Jammin
    Ben Jammin:
    Hmmmm:
    Again, no. ...
    Again, yes. I assure you when people ask you your weight, they have no concern of barometric pressures, distance from the mass you're being pulled by, nor which planet you're on.
    How is this relevant? I don't recall making any comments concerning what people mean when they say weight. I was commenting on a straight statement of what weight is, which, and if you ask any physical scientist they will agree, was incorrect.
    Ben Jammin:
    Also, when weight is measured, a significant portion of the time, it isn't measured within a vacuum.
    Again, I fail to see the relevance of this to any of my comments except for it basically agreeing with what I say in later comments.
    Ben Jammin:
    I'm also positive you're never been asked, "What is your apparent weight?" When someone want to know your weight, they want the number off the scale.
    Unlucky. I have actually been asked that question before though, admittedly, they wanted an explanation of the term and not the reading off my bathroom scales.

    The meaning or wants of the average person when talking about a large variety of topics bears little correlation to generally accepted scientific meaning.

  • x (unregistered) 
        o << "You have #{n} days to change your password."

    "Could you please fix our email generator? It has a bug where it makes things plural that should not be."

    "No prob, boss, consider it done."

        o << "You have #{n.to_f} days to change your password."
  • (cs) in reply to dkf
    dkf:
    my little phony:
    So if I bought a tank of helium, would they pay me to ship it?
    No. Helium's expensive (as anyone operating an MRI machine will tell you).
    MRI machines use liquid helium, which is even more expensive. And much colder.
  • (cs)

    Obviously, the packaging alone weighs 9.4 pounds. It's not a total. You know how they like to jack up shipping prices with ridiculous weight estimates.

  • (cs) in reply to Sam
    Hmmmm:
    It is incorrect to say that a helium balloon has a negative (or zero) weight. The weight of an object only changes when its mass changes or when the gravitational field changes.
    But remember that, in the case of a buoyant object, the effective gravitational field strength has diminished. The net force is negative, so the (apparent, or indicated) weight is actually negative.
    Star Wars+physics nerds:
    "May the net force be with you."
    Hmmmm:
    Most bathroom scales ... actually measure "apparent weight". This is only the same as weight in an inertial reference frame ... where gravity is acting vertically downward.
    Indeed. In what direction does gravity act on your world? ;-)
    Sam:
    Assuming the Earth is uniform, the gravitational force you feel decreases linearly from its maximum value at the surface to zero at the centre.
    Another, somewhat quirky, way to see it is: when r=0, the local volume therefore is zero; zero volume contains zero mass; zero mass exerts zero force.
  • (cs) in reply to Oinky
    Oinky:
    PedanticCurmudgeon:
    Oinky:
    The real WTF, by the way, is having a 3-month password change policy.
    I used to work at a place that had a 1-month password change policy. The users ended up writing their passwords on the first card in their Rolodexes, and even the sysadmin started using the month and year as the password.[image]

    (here, fixed that for you)

    Well, with a 3 month password change policy, the sysadmins would use the QUARTER and year as the password. Much less predictable ! :-D

    Thanks!

    I am surprised, though, that no one asked: "What's a Rolodex?"

  • Guest (unregistered) in reply to Hmmmm

    BZzt.

    What is the "down" direction in space ? For that matter, what is the "down" direction on/in of the Lagrange points?

    Your "apparent weight" is not directional, but just related to the/its mass and the ammount of energy-over-time that is needed to get something to move with a certain speed -- or to stop it moving if it has that speed.

  • (cs) in reply to Matt
    Matt:
    Freeview is pretty bad
    If your signal is OK, Freeview is an excellent TV service compared to the old terrestrial pile of shit the UK used to have to suffer. At one time people were celebrating because there was a new channel, which made a grand total of three 405 line VHF - all in monochrome. So don't moan about Freeview constantly, as it is, as its name implies Free of cost. There's FreeSat as well.
  • Sam (unregistered) in reply to Guest
    Guest:
    What is the "down" direction in space ? For that matter, what is the "down" direction on/in of the Lagrange points?

    Your "apparent weight" is not directional, but just related to the/its mass and the ammount of energy-over-time that is needed to get something to move with a certain speed -- or to stop it moving if it has that speed.

    It is mass that determines the amount of energy required to move an object, not weight; this is Newton's Second Law F = ma. (Note that the work done, i.e. the energy, is Fs - force multiplied by the distance over which the force was applied.) Weight is the force applied on an object by gravity.

    By definition, down is the direction in which the weight force points. If you're somewhere like a Lagrange point where there is no net gravitational force, there's also no weight and no defined down (other than towards the enemy's gate).

  • Bob (unregistered)

    Is anyone else wondering what kind of kitty litter can have a mass of 28 lbs and 14.1 kg at the same time?

  • (cs) in reply to Sam
    Sam:
    (other than towards the enemy's gate).

    +1

  • Your Name * (unregistered) in reply to Jay
    Jay:
    Hey, aren't the admins supposed to be anonymizing these posts? I really don't appreciate having my son's name, 3995599, posted on a public web site.

    If you look carefully they did anonymize it to 3195599. It's only because of your own stupidity that you accidentally revealed real name yourself.

  • f=ma (unregistered) in reply to Captain Obvious
    Captain Obvious:
    too_many_usernames:
    Hmmmm:
    Bzzzt! Wrong! Weight is a measure of the force that gravity exerts on an object. What you are describing is "apparent weight", the net, downward force exerted on an object.

    I weep for the future of humanity if this is the kind of thought process that is now being taught about science.

    That definition of weight is downright useless, as it would force you to weigh everything in a vaccume. Not to mention gravity is accelleration, not a force, and even if it was, weight isn't measured in gram-meters per squared second.

    Nope, it isn't. It's measured in kilogram meters per squared second... you were close though, I grant. :)

    (1 Newton = 1 kg * m * s^-2 )

  • Hmmmm (unregistered) in reply to Bob
    Bob:
    Is anyone else wondering what kind of kitty litter can have a mass of 28 lbs and 14.1 kg at the same time?
    No, because everyone else either, if they did notice it, has working eyesight and can quite clearly see the 28 has been crossed out and 31 printed above it or they just didn't notice in the first place...

    (+1 for calling it mass though :)

  • (cs) in reply to Hmmmm
    Hmmmm:
    (+1 for calling it mass though :)
    Too bad that according to the manufacturer, it's not mass but weight :)
  • Pedant (unregistered) in reply to Ben Jammin
    Ben Jammin:
    Hmmmm:
    Ben Jammin:
    Weight is actually the number on my bathroom scale.
    Again, no. ...
    Again, yes. I assure you when people ask you your weight, they have no concern of barometric pressures, distance from the mass you're being pulled by, nor which planet you're on. Also, when weight is measured, a significant portion of the time, it isn't measured within a vacuum. I'm also positive you're never been asked, "What is your apparent weight?" When someone want to know your weight, they want the number off the scale.
    For the same reason (or a very similar one), I'm always sure to ask people what the current measure of time is according to the Julian Scale given when adjusted for the Australian Eastern Daylight offset - I simply asked for the time once, and someone just gave me the number of microseconds from some arbitrary offset - the change must have been significant before I managed to work out what they meant in some meaningful representation....

    Given this site tries to attract IT people, I'll assume you're one as well - in which case you should know by now that what people ask is rarely what they actually want. Fortunately, most of us are smart enough to be able to interpret what they might want when they ask your weight (how rude). You're probably 100% correct that when people ask your weight they just want the number on the scale, however just because they ask the wrong thing doesn't make it weight....

  • Zhim (unregistered) in reply to PedanticCurmudgeon
    PedanticCurmudgeon:
    Oinky:
    PedanticCurmudgeon:
    Oinky:
    The real WTF, by the way, is having a 3-month password change policy.
    I used to work at a place that had a 1-month password change policy. The users ended up writing their passwords on the first card in their Rolodexes, and even the sysadmin started using the month and year as the password.[image]

    (here, fixed that for you)

    Well, with a 3 month password change policy, the sysadmins would use the QUARTER and year as the password. Much less predictable ! :-D

    Thanks!

    I am surprised, though, that no one asked: "What's a Rolodex?"

    Perhaps noone bothered reading your comment?

  • Blingo (unregistered)

    The Amazon one is no WTF....(well, not really) Couriers and post offices and things have wierd rules for shipping. Clearly, this package falls into the 30lb category, however Amazon's system needs to have some way to convert 20.6lb into 30lb - which they do by adding a shipping weight of 9.4lb. I guess they need to show (for user traceability) whty they paid 30lb (pound, not Pound) postage instead of the 20lb the consumer thought they could get away with....

  • Blingo (unregistered) in reply to Blingo
    Blingo:
    The Amazon one is no WTF....(well, not really) Couriers and post offices and things have wierd rules for shipping. Clearly, this package falls into the 30lb category, however Amazon's system needs to have some way to convert 20.6lb into 30lb - which they do by adding a shipping weight of 9.4lb. I guess they need to show (for user traceability) whty they paid 30lb (pound, not Pound) postage instead of the 20lb the consumer thought they could get away with....
    Also can't help but think Neil (Young Ones): "It means something REALLY, heavy...."

    (is it just me, or does that seem a bit heavy for a monitor stand?)

  • Frank (unregistered) in reply to K

    You can use it to measure negative weight if you put it on the ceiling!

  • Pfft (unregistered) in reply to lolwtf
    lolwtf:
    Obviously, the packaging alone weighs 9.4 pounds. It's not a total. You know how they like to jack up shipping prices with ridiculous weight estimates.

    My bet is that Uncle Al is right, and the shipping dept is using kilos. 20.6 Pounds is 9.34 kilos, close enough to be rounded to 9.4. For some reason the UI still shows it as pounds, though.

  • bags (unregistered)

    this is study examines the development of enterprise resource planningsystems an a means of inllustrating.

  • (cs)

    Greetings friend. I'm K Johnson, random Internet user. You might know me as a vital participant of the 1968 senate hearing on numeric email addresses, and you've most likely seen one of the many email addresses GMail was going to suggest to me but other people have somehow managed to steal from us. Black Mesa can eat my bankrupt...

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