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Help with a scientific explanation

Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
Ok im doing some physics coursework (oh yeah!) and I need help on wording the scientific explanation on why a model helicopter will fall slower the bigger the wing span is.
I know how it works i just dunno how to word it? I'm not going to use what people say directly, i'll put it into my own words. Or could anyone give me some good webpages? I've looked but i cant find any.
Thanks

Comments

  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    From my Physics A level, I think you are talking about centripetal acceleration, and velocity/ terminal velocity.
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    Iluv2party wrote:
    From my Physics A level, I think you are talking about centripetal acceleration, and velocity/ terminal velocity.
    not a clue.... :confused:
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    terminal velocity = The maximum speed of an object, reached when the forces moving the object are balanced by its frictional forces.


    but i think your more on about air resistance.
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    this explains it perfectly


    http://www.adl.gatech.edu/classes/dci/aerodesn/dci03.htm


    Cetripetal acceleration = velocity (squared)/radius

    the radius in this case is the lenghth of the wingsspan
    the longer the wingspan, the smaller the acceleration

    the velocity of the plane is taken to be the same, ie its at terminal velocity
    the plane falls in a circular motion so the force is directed to the centre and is downward and is opposed by friction, ie the drag.
    speed also = distance/ time
    you should be able to work it out from these equations.


    hope it helps
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    i'd of thought that the bigger the spinny things on the helicopter, the more aerodynamic lift is produced from more air running faster over the top?

    but i might be wrong :s
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    Iluv2party wrote:
    this explains it perfectly


    http://www.adl.gatech.edu/classes/dci/aerodesn/dci03.htm


    Cetripetal acceleration = velocity (squared)/radius

    the radius in this case is the lenghth of the wingsspan
    the longer the wingspan, the smaller the acceleration

    the velocity of the plane is taken to be the same, ie its at terminal velocity
    the plane falls in a circular motion so the force is directed to the centre and is downward and is opposed by friction, ie the drag.
    speed also = distance/ time
    you should be able to work it out from these equations.


    hope it helps
    That looks like TOTAL bollocks to me. Centripetal acceleration has nothing to do with it.
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    Fiend_85 wrote:
    That looks like TOTAL bollocks to me. Centripetal acceleration has nothing to do with it.


    well i didnt see you give an explanation so i think youre full of bollocks u twat
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    WTF has this to do with centripetal FORCE anyway. It has jack shit to do with it. If you can't answer question sensibly don't bother.

    Though all objects fall at the same rate if you ignore air resistance (i.e in a vacume) regardless of mass or size.
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    is this gcse? it all sounds extremely complicated to me, i dont remember doing anything as difficult as this! do you not have a text book or something that explains the basic principle that you could then relate to the helicopter?
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    Centripetal force has nothing to do with it, as I suspect Iluv2party spent too much time partying and not enough time doing his homework. But at least she spelled "twat" right, eh.

    As bomberman says, in a vacuum all objects will fall at the same rate. The reason why a larger wingspan would slow the model down in reality is simply because of wind resistance.

    An object accelerates when one force upon it is greater than the other. At first the force dragging the model down is greater than the force pushing upwards, which is the wind resistance. When the two forces are equal the model will fall at a constant speed unless one force increases (such as the force upwards when it hits the ground).

    The wingspan of the model affects the magnitude of the force pushing upwards, for obvious reasons. If the wingspan is large, then the force upwards is larger, and so the downward acceleration will be cancelled out quicker. This means that the larger aircraft will reach terminal velocity sooner, and therefore this downward velocity will be slower. The smaller aircraft has a smaller upward force, so will accelerate for longer before reaching terminal velocity.

    Remember two things: the upward force is not fixed, and increases exponentially as the downward velocity increases; terminal velocity is not a fixed number.

    Given that speed = distance x time, it then follows that if something is travelling slower over the same distance, it will take longer.
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    Having now read what you said again, I shall clarify what you should say.

    You should, before you start, clarify your theory. You must state that it is assumed both aircraft have an equal mass.

    First of all explain that acceleration is a result of the forces acting on an object being imbalanced. If the forces are balanced then no acceleration takes place.

    Second of all, explain that the downward force (in Newtons) is equal to the mass of the aircraft (in kg). This is because the force acting on the aircraft is simply gravity, which has a value of 1.

    Third of all, explain that the upward force is wind resistance to the aircraft, and that this wind resistance is exponentially linked to the downward velocity of the aircraft.

    Fourthly, explain that the extent of the upward force is dependent on the area of the wingspan. You assume that the wings have a mass of 0kg.

    Fifthly, explain that the aircraft stops accelerating when the upward and downward forces are balanced.

    Sixthly, explain that the larger wingspan means that the upward force is greater. This means that the forces are balanced sooner, given that the downward force is a constant. This, consequently, means that the smaller wingspan will allow for more accleration before the forces become balanced.

    Seventhly, state the relevant formulae for acceleration and for speed, mostly to show you know them.

    Eightly, state that given s = d.t, if an object has a greater velocity then it will travel the distance quicker.

    There are other things that you would need to assume, but these things are assumed without question at GCSE level. And, basically, I cba going into it any further, mostly because my A'Level mechanics is a bit rusty.
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    Iluv2party wrote:
    well i didnt see you give an explanation so i think youre full of bollocks u twat
    Wow, you really exonerated yourself there.

    I didn't give an explaination because the correct one has already been given by mel-h, I refuted your shite.
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    Is it not simply because of increased air resistance, as Mel says?

    Mass has no bearing on gravitational (downward acceleration) force.
  • SkiveSkive No discipline. No morality. No respect. New ForestPosts: 15,263 Skive's The Limit
    Kentish wrote:
    Is it not simply because of increased air resistance, as Mel says?

    Mass has no bearing on gravitational (downward acceleration) force.

    In a vacuum gravitational acceleration is the same for evey object here on earth's, something like 9.8 m/s/s so mass doesn't matter in a vacuum or with two objects that have the same drag.

    An object will continue to accelerate towards the ground until the force of drag equals gravity's pull on the object i.e it's mass.

    Mass does have an effect.
    Weekender Offender 
  • SkiveSkive No discipline. No morality. No respect. New ForestPosts: 15,263 Skive's The Limit
    Rotor blades are essentially airfoils (wings). The bigger the wings, the bigger the force working against gravity.
    Weekender Offender 
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    Skive wrote:
    gravity's pull on the object i.e it's mass.

    Wrong. Very wrong. Also completely wrong. gravity's pull on an object is not mass. That's basic GCSE physics. Go check.

    Kermit summed it up pretty well so I wont bother re iterating what was said now I have more time for a proper reply. At least I skim read over what he wrote and it seems OK.
  • SkiveSkive No discipline. No morality. No respect. New ForestPosts: 15,263 Skive's The Limit
    Wrong. Very wrong. Also completely wrong. gravity's pull on an object is not mass. That's basic GCSE physics. Go check.

    Sorry I meant weight.
    Weekender Offender 
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    hey listen, I tried to help her, i didnt say i knew the answer and i did say that she needed to check what i posted.

    if you know better than me then tell her the answer but dont slag me off seeing as thought i was just being helpful and honest.

    solve her question, dont critisise me i was trying to help.
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    Iluv2party wrote:
    hey listen, I tried to help her, i didnt say i knew the answer and i did say that she needed to check what i posted.

    No you didn't.

    You must be losing your memory. Maybe you should party less, its obviously getting to you.
    dont slag me off

    Why not?

    I won't, but only because it would be no fun if your best response would be "you twat".
    i thought

    Lies, tbh.
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    Iluv2party wrote:
    hey listen, I tried to help her, i didnt say i knew the answer and i did say that she needed to check what i posted.

    if you know better than me then tell her the answer but dont slag me off seeing as thought i was just being helpful and honest.

    solve her question, dont critisise me i was trying to help.

    Don't hijack the thread. You said "this explains it perfectly" you were corrected with no personal attack and then you started calling people a twat. Nobody slagged you off. Get over yourself.
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    Skive wrote:
    In a vacuum gravitational acceleration is the same for evey object here on earth's, something like 9.8 m/s/s so mass doesn't matter in a vacuum or with two objects that have the same drag.

    An object will continue to accelerate towards the ground until the force of drag equals gravity's pull on the object i.e it's mass.

    Mass does have an effect.
    The question was about how quickly it falls. The gravitational pull is the same as you say regardless of mass, but terminal velocity will differ according to air resistance.
  • SkiveSkive No discipline. No morality. No respect. New ForestPosts: 15,263 Skive's The Limit
    Kentish wrote:
    The gravitational pull is the same as you say regardless of mass, but terminal velocity will differ according to air resistance.

    The gravitational pull is stronger in larger masses that's why they're heavier, but gravitational acceleration is constant in a vacuum for all objects (9.8m/s/s).
    Weekender Offender 
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    Skive wrote:
    The gravitational pull is stronger in larger masses that's why they're heavier, but gravitational acceleration is constant in a vacuum for all objects (9.8m/s/s).
    You know what I meant, cheeky monkey. :p

    Gravity is the same outside a vacuum too, but varies with altitude.
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    Kermit wrote:
    Having now read what you said again, I shall clarify what you should say.

    You should, before you start, clarify your theory. You must state that it is assumed both aircraft have an equal mass.

    First of all explain that acceleration is a result of the forces acting on an object being imbalanced. If the forces are balanced then no acceleration takes place.

    Second of all, explain that the downward force (in Newtons) is equal to the mass of the aircraft (in kg). This is because the force acting on the aircraft is simply gravity, which has a value of 1.

    Third of all, explain that the upward force is wind resistance to the aircraft, and that this wind resistance is exponentially linked to the downward velocity of the aircraft.

    Fourthly, explain that the extent of the upward force is dependent on the area of the wingspan. You assume that the wings have a mass of 0kg.

    Fifthly, explain that the aircraft stops accelerating when the upward and downward forces are balanced.

    Sixthly, explain that the larger wingspan means that the upward force is greater. This means that the forces are balanced sooner, given that the downward force is a constant. This, consequently, means that the smaller wingspan will allow for more accleration before the forces become balanced.

    Seventhly, state the relevant formulae for acceleration and for speed, mostly to show you know them.

    Eightly, state that given s = d.t, if an object has a greater velocity then it will travel the distance quicker.

    There are other things that you would need to assume, but these things are assumed without question at GCSE level. And, basically, I cba going into it any further, mostly because my A'Level mechanics is a bit rusty.

    i dont get the second point :confused:
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    Weight (N) = mass (kg) x gravity. Therefore a plane would weigh e.g. 100kg x 1= 100N.

    The downward force (N) = weight (N)

    Therefore the downward force is 100N, in this example.

    I hope someone can confirm if that's right- as I said, my mechanical mathematics is a tad rusty, as I haven't used it for nearly five years.
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    You're wrong actually Kermit. The value for the acceleration due to gravity is 9.81m/s^2

    Hense the equations F=ma, Force [N] = Mass [kg] X Acceleration [m/s^2]
  • Former MemberFormer Member Posts: 1,876,324 The Mix Honorary Guru
    Fiend_85 wrote:
    You're wrong actually Kermit. The value for the acceleration due to gravity is 9.81m/s^2

    Hense the equations F=ma, Force [N] = Mass [kg] X Acceleration [m/s^2]
    i ended up not using it anyway, i did a search and got it off a gcse website
    all that still looks like a foreign language to me - then again physics isn't my best subject
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