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  • #841637
    OneOfMany
    Participant

    Because everything else is also moving.

    #841638
    feivel
    Participant

    even if you close your eyes the effect is the same

    #841639
    OneOfMany
    Participant

    Why would that make a difference?

    #841640

    According to Newton’s Second Law:

    F=ma

    where “f” is force (Newtons), “m” is mass (kg), and “a” is the acceleration of the object (meters/second^2). Every force you feel has its roots in this fundamental equation.

    Therefore, when one stands on Earth, we don’t feel any outside force of the movement of earth, because there is no acceleration (velocity of the rotation of Earth is constant). Therefore, F=0. However, in the case of an accelerating car, F>0.

    To answer the question of getting dizzy on a roller coaster/merry-go-round: that has to do more with changing perspective; on Earth, everything moves together in unison. But on a roller coaster, the perspective is not moving at the same speed as you are – therefore, there can be dizziness.

    #841641
    brainy
    Participant

    thecurious one, I have a question. HOw many chromosomes are there after telphase? 46 or 92?

    #841642

    There would be a total of 23 chromosomes per cell (a total of 46).

    #841643
    Pegger
    Member

    Do you feel like you’re traveling 250 km/h on an airplane? Unless you’re accelerating significabtly, you can’t really feel it unless you can clearly see that you’re moving at a different speed than your surroundings. (Look up inertial reference frames.)

    #841644
    feivel
    Participant

    no. no and no

    it has nothing to do with the frame of reference, it has nothing to do with seeing things around you. forget “dizziness, that was a bad way of putting the question, think in terms of “feeling” the turning.

    the situation will be the same if the merry-go-round is located alone in outer space, just as the earth is

    here is an easier way to look at the problem, instead of talking about human perception:

    say you have a measurement device with you that measures centrifugal “force”.

    although the merry-go-round (now relocated in outer space, off the earth)is rotating at a speed of say 5 miles per hour, and the earth is rotating at 1,000 miles per hour, the centrifugometer will measure over 10,000 (something like that, i didnt actually calculate it) times the amount of centrifugal force on the m-g-r than it does on earth. why is that?

    if the m-g-r would move at 1,000 miles per hour (as does the earth) you would be instantly and violently thrown off, even if the m-g-r had the same gravity as the earth does. why arent we thrown off the earth?

    #841645
    feivel
    Participant

    the answer is a matter of very elementary (1st year high school or even less) beginning physics.

    you need to know the basic definition of “accceleration”, and the difference between “velocity” and “speed”

    #841646
    Pegger
    Member

    Centrifugal force is fictitious. What you are talking about is centripetal force. And by the nature of circular motion, you’re ALWAYS accelerating.

    #841647
    feivel
    Participant

    yes pegger, notice my use of the quotation marks: centrifugal “force”.

    nevertheless, because i am not speaking to a group of physicists it is perfectly acceptable to use the common term: centrifugal force, as it IS an “apparent’ or “virtual” force though not a force in the strict sense.

    and yes you are always accelerating when moving in a circle. do you have an answer to the question: why is the centrifugal (if you prefer: centripital) force greater on the slowly moving mgr than on the rapidly moving earth?

    #841648
    OneOfMany
    Participant

    i am not speaking to a group of physicists

    With Pegger here, I’m not so sure…:)

    #841649
    Pegger
    Member

    Centripetal force doesn’t have much to do with the dizziness. While it’s true that the earth is moving more rapidly than the merry-go-round, in fact, one’s ANGULAR velocity is much, much less than on a merry-go-round. This is why you wouldn’t get dizzy.

    #841650

    feivel-

    The answer to that question is that the force of gravity on earth is greater than the “force” that accelerates you away from tangential velocity that would be expected due to the rotation of the earth. To put that in easier terms to understand: we don’t feel as if we are falling off the earth because gravity keeps us here. Without gravity, we would “fall off” the earth as well.

    #841651

    And I had a question for you guys as well:

    What is beta oxidation, and why does it help camels?

    #841652
    feivel
    Participant

    right

    the angular velocity is the only parameter that involves acceleration, and therefore the perception of movement.

    the mgr goes through a full circle in about 1/2 a minute while the earth rotates through a full circle in 24 hours.

    so in terms of RPM (revolutions per minute) them mgr is actually moving about 2,500 times faster than the earth.

    #841653
    feivel
    Participant

    thecurioseone

    no

    the centripital force is unnafected by gravity

    it is true that the net force on an object situated on a rotating body (the net force acting to keep the object on the body or away from the body, (ie the weight, in simple terms) is influenced both by the force of gravity vs the rotational (angular) acceleration, but those two parameters have zero influence on each other.

    in other words, a device which measures centripital force would give a reading thousands of times greater on the mgr than on the earth even if the mgr would somehow have a pull towards the center equivalent to earths gravity. that was the essence of the question as i restated it. the original question was not clear as i should have not used “dizziness” as the main differential factor between the two cases. i tried a couple of times to fix that.

    #841654
    samhachaim
    Member

    Beta oxidation is when saturated fatty acids are broken down and two carbon units are removed with each turn of the cycle. The oxidation of fats results in a large quantity of water so camels who don’t have adequate access to drinkable water obtain their water requirements from the complete oxidation of fats.

    #841655
    feivel
    Participant

    curiousone;

    to put it another way, even if the earths gravity were to suddenly completely cease, we would not go flying off the earth. in fact the centrifugal force would be so negligible as to be “practically” non-existent. picture an ant sitting on the end of the HOUR hand of a smoothly moving analog clock (not one that “ticks”). how much centrifugal force is that ant experiencing from the movement of the hand. that hand is moving at the same angular acceleration as the earth.

    [of course you would have to make SOME kind of effort to stay put such as touching any object attached to the earth, say a tree. the friction of the slightest touch would keep you from slowly eventually floating away, as long as you didnt make any kind of motion against the earth, such as walking.]

    #841656
    feivel
    Participant

    What is beta oxidation, and why does it help camels?

    see here:

    http://www.theyeshivaworld.com/coffeeroom/topic/the-camel-and-the-desert

    #841657
    samhachaim
    Member

    Beta oxidation is when saturated fatty acids are broken down and two carbon units are removed with each turn of the cycle. The oxidation of fats results in a large quantity of water so camels who don’t have adequate access to drinkable water, obtain their water requirements from the complete oxidation of fats.

    #841658
    Pegger
    Member

    Centripetal force is not a force that exists in its own right. In order for an object to remain in circular motion, there needs to be a force ALREADY pulling the object towards the centre of the circle to PROVIDE centripetal force.

    For example, in swinging a yoyo in a circle, the force of tension provides centripetal force. When a car drives around a sharp curve, the force of friction provides centripetal force. And when a person stands on the Earth, the force of gravity provides centripetal force.

    Therefore, if Earth’s gravity turned off, a person would simply continue to follow his tangential velocity and fly off into space. (Of course, the whole planet would have disintegrated as well, so you might not notice.)

    #841659

    feivel-

    Actually, if gravity would cease, you would fly off the earth. There would be absolutely nothing holding you to the ground. And friction would also cease, because the equation for friction:

    F(f)=uF(n)

    where “u” (actually, really the Greek letter mew, the frictional coefficient), and N(n) is the “normal force”, which is

    F(n)=mg

    where “m” is the mass and “g” is the gravitational constant. So if “g” is zero, then F(n)=0, and consequently, F(f)=0 (there would be absoluteley no friction).

    So…gravity is the only thing holding us here 🙂

    #841660
    OneOfMany
    Participant

    (Of course, the whole planet would have disintegrated as well, so you might not notice.)

    “…it would probably have been a great satisfaction to her to know that in a minute and a half or so he would suddenly evaporate into a whiff of hydrogen, ozone and carbon monoxide. However, when the moment came she would be too busy evaporating herself to notice it.”

    tee hee

    #841661
    feivel
    Participant

    You would not fly off into space

    You would slowly rise based on the angular velocity

    The centripital force is supplied by the friction as i described

    And curiousone you are way off. the second equation is only a particular application of the general

    Equation

    Gravity is in no way reqired for friction

    Friction can in fact act in opposition to gravity

    This is basic

    #841662
    Pegger
    Member

    feivel – a person would move according to his tangential velocity, not his angular velocity. Angular velocity is only pertinent to circular motion, and he would no longer be spinning – that’s the point. A person’s tangential velocity at the surface of the earth is almost 30 km/sec! I’d call that flying, not “slowly rising”…

    But you’re right that gravity isn’t required for friction. Normal force is required for friction. While it’s true that normal force often comes from gravity, it doesn’t have to! It’s another one of these forces that doesn’t really exist in it’s own right…

    #841663
    mto
    Member

    when writting the fourth quantum number Ms ther’s is a value of 1/2 or -1/2 does it makes a difference which electron gets which value?

    #841664

    feivel-

    Pegger is absolutely right – it doesn’t necessarily have to be gravity. However, on our planet, that is the ONLY acceleration means we have (we do not have a string tied around us and the center of the earth!).

    That is basic, my friend. Look at the frictional force equation I wrote before – that’s the force due to friction. Nothing more, nothing less. There needs to be an acceleration for the normal force to be >0; that comes from the acceleration due to gravity, in our case of us standing on planet earth.

    And mto – it does not matter; as long as each electron in the orbital have opposite values.

    #841665
    feivel
    Participant

    pegger

    let me give it one more try

    if you dont agree with the analysis we can leave it as a disagreement

    indeed you stop spinning.

    which has no effect on your tangential movement which is directly perpendicular to the direction of the force of gravity

    you will continue to move in a linear 30k/s exactly as you did before due to there being no force to act to change your momentum. as you continue to move in a straight line tangential to the earth at 30k/s, the earth continues to move below you at a speed of 30k/s as before thus there being no change in your situation relative to tangential movement in relationship to the earth.

    what does change is that as you say you are no longer spinning. what does that mean? it means that your ANGULAR VELOCITY is now null, you areno loner changing direction in concert with the earths angular velocity. your angular velocity has now become zero since the source of the centripital force has been removed.

    but now the difference between your angular velocity (zero) and the earths angular velocity (a very small 1 revolution per 24 hours) and you will gradually rise away from the spot of earth below you as it continues to change direction, and you do not.

    but as far as your tangential movement relative to the surface of the earth nothing has changed by the cessation of gravity. you are moving at 30k/s (as a result of your momentum which no force has altered, and the earth is moving under you at that same 30k/s just as before, as similarly no force has acted to change this.

    you will slowly rise as the the earth spins and you are no longer spinning with it.

    if you dont get it, try this thought experiment:

    you lift yourself with a crane to 500 feet above the earth (the 500 feet-crane part of this isnt necessary but it might help to prevent certain misunderstandins) you are equipped with downward pointing thrusters exactly equal to the effect of gravity on you.

    as the crane releases you, you turn on the thrusters. you have now eliminated all centripital force and are no longer “spinning with the earth” are you going to suddenly fly away at 1,000 miles per hour? of course not, but you will very slowly become more distant from the earth as the earth contues to turn.

    feel free to submit your rebuttal but i quit, thanks for the interesting discussion

    #841666
    BTGuy
    Participant

    Reasons people dont go on a second date?

    #841667
    feivel
    Participant

    from the cornell dept of astronomy:

    link to the “article”:

    http://curious.astro.cornell.edu/question.php?number=284

    What would happen if the gravity on Earth was suddenly turned off?

    ….In buildings, people would start floating gently upwards until they bumped into the ceiling. Outdoors, however (or in buildings with GIANT ceilings), things would start floating away from the Earth gently but eventually go much faster, as their straight lines took them farther and farther away from the circular path that the spinning Earth takes.

    …In fact, the force you would need to hold on and keep yourself from flying away from the Earth is very weak, only about 0.3% as strong as the force of gravity (and even weaker away from the equator).

    emphasis is mine

    #841668
    OneOfMany
    Participant

    What would happen if the gravity on Earth was suddenly turned off?

    ….In buildings, people would start floating gently upwards until they bumped into the ceiling. Outdoors, however (or in buildings with GIANT ceilings), things would start floating away from the Earth gently but eventually go much faster, as their straight lines took them farther and farther away from the circular path that the spinning Earth takes.

    …In fact, the force you would need to hold on and keep yourself from flying away from the Earth is very weak, only about 0.3% as strong as the force of gravity (and even weaker away from the equator).

    I think you forgot some emphasis.

    #841669
    Pegger
    Member

    feivel – My rebuttal shall be limited to the sentence you replaced with a “…” from that article:

    “Things not attached to the Earth in any other way would fly off into space in a straight line that would take them away from the surface of the Earth.”

    Thanks for the discussion.

    #841670
    feivel
    Participant

    Eventually they would go much faster

    Has nothing to do with this discussion

    that is referring to the eventual perceptual conversion

    of the perceived movement of the object in question from that

    Relative to the surface of the earth

    to that relative to the earth as a whole body

    which would be on the order of weeks to become significant.

    As to your rebuttal pegger i am disapointed

    I thought you would exhibit some honesty

    We all can be wrong sometimes

    the article was quite clear as to the nature of what was meant by

    flying.

    His description was not at all compatible with

    a veocity of 30k per second.

    #841671
    feivel
    Participant

    I of course wholey agree with your rebuttal pegger

    I always said one would go flying off the earth

    I only said it would be slowly not at 30 kilometers per second

    Which is not compatible with the description from cornell

    I truly am sorry you chose to end the discussion like this

    #841672

    Pegger-

    feivel-

    ===============================

    As the atmospheric pressure decreased, all water would begin to boil (the precise temperature at which each ocean, river and lake boiled would depend on temperature, salinity, latitude and elevation) until there was no water left on Earth.

    #841673
    Pegger
    Member

    Aha, I think I see where we differ in this ridiculous hypothetical discussion. You see, I was assuming that if gravity was turned off, the planet disintegrated. It’s pretty much impossible to predict how the laws of physics will behave if you’re starting from the premise that certain important laws will be ignored.

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