Need help with physics question

[Duke]

During my holiday a while back me, my wife and a hotel neighbour came into an argument about a few things. The debate became quite heated after a few glasses of wine and my wife gave up while me and the other guy continued for a while with quite advanced math equations.

I have his e-mail and swore that if I was wrong then I would write "I love Hull" on my chest and get a picture pf it on a public place in Sweden and mail it to him. (he lives in Hull, UK) he would do similar so a lot is a stake here.

I thought for a split second that Nick was a physist but he is in fact a chemist. I got some answers from him and used him as a reference but that guy had some other guy claiming different answers. Like anyone in Hull has any education at all. Anyway, I need good solid proof to my questions and I need a source to point to when he tries to weasel out of it.

Do all people in Hull speak with a thick accent? After a few beers he was close to impossible to understand. I kept telling him QUEEEEENS English, not that mining lingo but he just waved me off and told me to listen up.

Question 1.
(please try to overlook the somewhat "childish"
enviroments of the examples)

If I were to drop a turd standing up in a bus moving
50 mph, is the turd then: (A) Moving in 50mph as the
bus, (B) Slowing down from 50mph and be moving at
slightly below 50mph when it hits the floor of the
bus, or (C) not moving forward at all i.e. 0mph and
only moves towards the earth due to the laws of
gravity and falling objects?

My standpoint here is that it has to be slowing down
but not enough to be noticed from the crack to the
floor (his "evidence" was that the turd would drop
right beneath him. He claimed to have empiric
evidence of this *roll*). If I had my butt hanging
through the window of the bus then the turd wouldnt be
travelling along with the bus since no force is
keeping the turd in motion. My answer is then (B)

Question 2
If I spit from the balcony of the hotel and so to
speak "launched away" the spit by thrusting my body
and neck forward to sort of throw the spit out of my
mouth. Is this positiv or negative to the distance
the spit will travel in the air?
(A) It will go further since the move put the spit in
motion prior to it leaving the mouth and therefore
accelerated the inertia of the ball of spit
(B) It will not make any difference. The mouth
technic is all that matters
(C) It will have a negative effect since the body
moved faster then the spit before it leaved the mouth
and therefore subtracted its inertia.

My answer, (B) since I see no reason why it would
help.

Question 3 (and this is a tricky one)
Who would win in a fight between a nest of bees and a
community of fireants.
(A) the bees
(B) the fireants
and why.

My answer would be the bees mostly because they are airborne and could do airstrikes against the grunts.

After my mail to Nick we have added a question that works as some sort of back-up question. If we cant decide a real answer to any of the above then this one kicks in.

Question 4
If a seagull sneaked its way into an airplane and stayed down until it was airborne. What would happend to the weight of the plane if it started flying inside the cockpit?
(A) The plane would weigh more
(B) The plane would weigh less
(C) It would make no difference

My answer is that it would make no difference. The bird is already inside the plane and no matter what it does it would somehow affect the total weight in some way to keep it constant. I dont really know why though so I cant claim a win.

[Protput]

the only thing I can say is about the spit. It definitely goes a lot further if you thrust your head.(it already has some speed when it comes out)

...

or something

[Duke]

Now, you see this is an opinion. I cant refer to this as actual proof. The only time an opinion from a dutch guy has any impact at all on a working class bloke from Hull is when it is about places in Amsterdam you can find things to smoke.

[Polymorphic]

Ok, I'll bite...

Question 1.

If I were to drop a turd standing up in a bus moving
50 mph, is the turd then: (A) Moving in 50mph as the
bus, (B) Slowing down from 50mph and be moving at
slightly below 50mph when it hits the floor of the
bus, or (C) not moving forward at all i.e. 0mph and
only moves towards the earth due to the laws of
gravity and falling objects?

If you're inside the bus, then A, if you hang your rear out of the window then B - the bus is moving, therefore you are too, therefore the turd is too. For it to slow down something has to push sideways on it - normally air-resistance - which won't be present if you're inside the bus with all the windows closed.

Question 2
If I spit from the balcony of the hotel and so to
speak "launched away" the spit by thrusting my body
and neck forward to sort of throw the spit out of my
mouth. Is this positiv or negative to the distance
the spit will travel in the air?
(A) It will go further since the move put the spit in
motion prior to it leaving the mouth and therefore
accelerated the inertia of the ball of spit
(B) It will not make any difference. The mouth
technic is all that matters
(C) It will have a negative effect since the body
moved faster then the spit before it leaved the mouth
and therefore subtracted its inertia.

A, obviously. Just as if you spit when running.

Question 3 (and this is a tricky one)
Who would win in a fight between a nest of bees and a
community of fireants.
(A) the bees
(B) the fireants
and why.

No idea, they'd probably both give up and go home...

Question 4
If a seagull sneaked its way into an airplane and stayed down until it was airborne. What would happend to the weight of the plane if it started flying inside the cockpit?
(A) The plane would weigh more
(B) The plane would weigh less
(C) It would make no difference

This really depends, on average it won't make any difference - but because of the way that birds fly (push down, glide, repeat) then if the bird is currently pushing down then that force will be pushing down on the plane (increasing the weight), but if it's gliding then it'll be in free fall and not pushing down on the plane at all (or as much as it would just standing on it).

[Duke]

In Q1, the a** is inside the bus.

I dont see the obvious in Q2. Is this a brit thing since this is almost the exact words that he.... ....where are you from btw?

Still claiming flying things over earthbound in Q3

And in Q4 I say that you need some sort of aircurrent to glide so this in no option for the bird and even so the wings will press air towards the floor (is that the name) of the plane and keep the weight at a constant.


Should I send regards from a guy in a game on the internet that is nicknamed Poly?

I need evidence here. Why is it the way you say it is?

[korexus]

Let's have a go. It's been a while since i did mechanics though...

The things to remember with these are Newton's Laws of Motion which you can find in any mechanics book and probably on about a million webpages.

To summarise:

1) Everything carries on moving at the same speed at the same direction unless you kick it.

2) The change in speed and direction is depends on how how heavy it is and how hard you kick it.

3) How ever hard you kick it, it kicks you back just as hard.

So, for question 1) The turd starts off moving at the same speed as your ass because it is inside the ass. The only force acting on it is you pushing it out, so if this were a purely downward motion it would land directly below your ass. If you were sticking your ass out of a window it would slow a bit due to air restance and if the bus turned, the turd wouldn't and someone would get hit in the face.

For an example: Some Roman dude proved this by dropping stones from a moving chariot. It's quite famous but I didn't listen in that lecture, so I don't remember his name.

Question 2) Immediately before you spit, the saliva is in your mouth and travelling at the same speed as your head. You then 'kick' it by spitting so it will speed up further allowing it to reach a higher speed that if you hadn't moved your head. Of course for this to work you need to spit while your head is moving so you may need to work on 'technique' here to maximise the distance...

Question 3) I imagine that 1 on 1 a bee would win, but it's hard to say even there. Their stingers aren't as effective as say, a wasp, so it might have difficulty using it on something like an ant. How many insects are in each nest? Certainly, given sufficent numbers the fireants *could* win...

Question 4) Technically you are right. The total mass of the plane is the combined masses of the plane and everything inside it. The total weight of the plane is this value multiplied by the force of gravity. This isn't changed by the bird at all. However, the force required to keep the plane aloft will be marginally higher on average as the bird is creating a downward force in order to keep itself aloft. This would make it 'feel' heavier but not actually increase the weight...

As an (interesting) point, the weight of the plane is actually slightly less, although not because of the bird. It's further away from the earth and so the gravitational pull has marginally less effect on the plane...


Hope that helped a bit...


korexus.

[TK]

Good post Duke.

[Protput]

Now, you see this is an opinion. I cant refer to this as actual proof. The only time an opinion from a dutch guy has any impact at all on a working class bloke from Hull is when it is about places in Amsterdam you can find things to smoke.

actually I'm not Dutch! I'm from Belgium, which is a big difference, we're no pot-heads and we have some beer that doesn't taste like it's already been drunk once or twice

[Duke]

Chill, or we might think we found a weak spot and continue to hit it.

Ok mr Exodus. Let me see if I got this right.

On Q1, the turd is in fact moving at the same speed as the bus.

On Q2 you claim that the spit will reach a higher speed with the kick. I beg to differ. I say that you can reach the same distance standing still but that it would be easier with the kick. The limit would not change.

On Q3 I might have used the wrong word for the insect. It might be wasp I am looking for. I need to clear this with Hull. The insect I am talking about have jaws and is actually a predator eating meat.

On Q4, sooo the mass of the plane is constant or? You are confusing me with stuff that are beside the point.


And I still wonder if all people in Hull talk wierd.

(Thanks TK, that is what I am here for )

[korexus]

On Q1, the turd is in fact moving at the same speed as the bus.

Yup.

On Q2 you claim that the spit will reach a higher speed with the kick. I beg to differ. I say that you can reach the same distance standing still but that it would be easier with the kick. The limit would not change.

I guess there is a limit on the speed you can get the spit to, a sort of terminal velocity for saliva. Therefore if you're very good at spitting then the jerking of the head will have a negligable effect. I have no idea what this maximum speed would be, but I imagine it's higher than you can produce and even if this were the case the head movement would help a marginal amount by increasing the original velocity of the spit. Maybe we should fund some experiments?

On Q3 I might have used the wrong word for the insect. It might be wasp I am looking for. I need to clear this with Hull. The insect I am talking about have jaws and is actually a predator eating meat.

Bees have hooked stings and make honey. Wasps look pretty similar but have straight stings and are generally nastier, same goes for hornets and probably a bunch of other things. A wasp would beat a fire ant 1-1 imho, but I'd say 10 fire ants could take down a wasp so it gets back to numbers again...

On Q4, sooo the mass of the plane is constant or? You are confusing me with stuff that are beside the point.

The mass is constant and therefore the weight (The downward force on the plane due to gravity) is constant. The total downward force may vary, but that doesn't matter.

And I still wonder if all people in Hull talk wierd.

They do.

(Thanks TK, that is what I am here for )

Hey this is serious! Were talking about the pride of, erm, Hull.


korexus.

[Donut]

If you're about to lose the arguement, just claim that it's all relative and it's impossible to answer the question without establishing a reference atmosphere for the problem. There's no arguement against it... everything is relative.

Or, my next answer would be: There's no such thing as Heat.

Donut

[Xechortariaste]

Q1 seems to have been adequately answered, so...

Q2, only thing I have to add is that a lot of it probably depends on the spitting techniques used within the mouth, and that some of these techniques could get a lot farther without the head motion than others with the head motion. So, when doing research, you'd have to be careful to use the same inter-buccal technique. (Inter-buccal being a new word I just learned meaning inside the mouth.)

Q3, you're probably right that, 1 on 1, a wasp could take out a fireant, and that numerous fireants could take out a single wasp, but this is a whole nest of wasps and a whole community of fireants. Now from what I've found, the size of a wasp colony greatly depends on the type of wasp. The colonies of paper wasps vary between 15 to 200 individual wasps, while yellowjackets can have up to 15,000. Honeybees can have as many as 60,000 workers in a colony, and unlike in WOK, if the colony is threatened, the workers will fight. On the other hand, a colony of fire ants that is at least a year old will have as many as 100,000 workers, and the largest and strongest colonies have been known to have 300,000 workers, so if we assume average colony sizes for both the ants and the wasps, the ants will have a tremendous advantage in numbers, possibly 20:1. I think this is enough to overcome even the advantage the wasps have with flight. In addition to this, it seems unlikely that a wasp, outnumbered 20:1, could get into an ant colony, navigate the dark corridors and find the queen to kill her. The fire ants, however, could swarm the beehive, and although many would be lost, their sheer numerical advantage would enable them to reach the queen and kill her. Here's some websites where I found the information on numbers:

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7450.html
http://www.greensmiths.com/bees.htm
http://www.ent.uga.edu/docs/fire_ants_in_georgia.htm

Q4, I agree that the weight would not change, but I would question whether there would be any net increase in downward force at all? Newton's Third Law holds that there will be an equal and opposite reaction to every action, or, if you kick it, it kicks back just as hard. Thus, the bird would create just as much of an upward force on the plane as it would a downward force, at least, it seems to me.

[korexus]

I pass the crown. This guy has even more time to spend looking round the internet than me!

Hey, I don't suppose you want a job helping finish WoK-On, etc?


As for the bird thing, I've already had lengthy conversations with a mate who does physics about it. (He used to play WoK, I just asked TK what his player name was and I've already forgotten!) In the end he agreed I was probably right, but it's pretty heavy stuff. If you care I'll explain, but I don't want to make Duke's head hurt...

[Xechortariaste]

Lol. Hey, I never claimed to have a social life. If I could help finish Wok-On, I'd be more than happy to... it would allow me to put off those papers I have to write even longer! But, I also never claimed to know anything about programming... I learned rudimentary HTML maybe five years ago, and that's it. I'm also not much of a physics person, but I'm always interested... So the actual mass stays the same but the downward force does increase?

[Duke]

Nice work my friends.

However this will not be settled anytime soon.

He won Q1. (My answer was B)

We are still undecided about Q2 and have therefore chosen to kick in Q4.

About Q3 we are arguing. I described the insect I was after and he called them bees, not me. I specificly used the phrase "not the ones that produces honey, the otherones that only is there to sting you and get in your glass of lemonade". He says that if we called them bees, then bees it is. He went with the ants, I still say wasps but I am willing to give in to the math situation. We werent clear on that when we made the question.

On Q4 I am right and he is wrong since he said that if the bird weighs 20 pounds then the plane will weigh 20 pound less while it is flying around inside it.

Oh, and I told him that I now have people confirming that he does talk wierd and that it wasnt me who didnt listen up. He says that it isnt people in Hull that talks wierd, it is everyone outside of Hull and especially people in some parts of London. I guess he is talking about that Cockney accent or something.

[korexus]

So the actual mass stays the same but the downward force does increase?

Just like 'Morph suggested, if the bird is gliding (which it could do for a while, eg from one end of the plane to the other like a thrown paper plane) the downward force is the same. (Air supports the bird, the floor supports the air) so plus or minus a bit of tubulence around the wings it may as well be sat on a seat.

If it's trying to gain height though it exerts a force on the air around it using N-II and N-III to move upwards and pushing everything around it downwards so if you were trying to lift the plane it would feel heavier.

'Morph was right, he just lost out on a technicality

NB, if your gut reaction was to say 'the plane is a closed system, the bird is inside it so it can't affect the overall force' you're in good company but you forgot that the soure of gravity is outside the plane. Me sitting on my chair is a closed system, but if you were to try lifting it, you'd find it much easier if I sat still than if I jumped up and down on the chair... (I just know someone's going to come up with a comment about that. )


korexus.

[Xechortariaste]

Yes, I have no life, but... it occurred to me that the difference between bees and wasps could make all the difference. I still say wasps would lose to the ants, but bees would have several advantages. For one thing, the typical beehive has 60,000 bees, as opposed to the mere 15,000 wasps. Furthermore, the hives of honeybees are filled with honey! There's no way ants could get into the hive and kill the queen with all that honey. And bees would fare no better in the ant colony, so it would have to be a battle for simple dominance, not to the death. In this case, I think the bees can overcome 5:1 odds much easier than the wasps at 20:1 odds.

[Dameon]

I don't think that question 1 has been answered correctly. I initially told Duke I thought the answer was C, but reading all this here (and brushing up on my Newtonian physics) has made me reassess my position. I now believe the correct answer is B. To understand why, you really have to look at the basic concept of velocity and how it's related to this question.

The 50 MPH in this question is horizontal velocity- the bus is moving forward, but it's not moving up and down. Yes, gravity is pulling it down, but the concrete (or whatever it's driving on) is pushing it up equally, so the vertical velocity is nullified. If you drop a turd on the bus, however, there's nothing pushing up against it until it hits the floor of the bus, so there is a negative (downward) vertical velocity. That turd is still moving at 50 MPH horizontally unless something stops it, but if you apply the negative vertical velocity to it, the total turd velocity will be reduced. The true velocity of the turd is the vector between both the horizontal and vertical velocities, and that vector is going to have a velocity that is less than 50 MPH.

Also to consider, once that turd hits the air, it slows down infintesimally. There may not be wind hitting it, but there's definetely some air molecules between it and the ground, and it WILL hit a lot of those molecules on the way down. This will slow the turd down; it might not be a measurable amount but it will be moving slower than when it first dropped. That's the other side of why it's not moving 50 MPH. It should be close to that speed, but it's true velocity would be less for the two reasons outlined above.

As for question 2, I really don't know the answer to that, so I'm going to leave it alone.

Question 3, the wasps individually, but if we are going will full communities, then as Xecho quite adequately explained the ants would just have an overwhelming numerical advantage.

And as for number 4, I think the overall weight of the plane would stay the same for the reasons that Korexus described in re to the mechanics of birds flying.

[Duke]

Well then. This is intresting. Way to go mr Chemist.

I'll inform my "friend" about this little turn of events.

Still say the wasps or bees or whatever would win since they could fly low above the fireants and drop burning objects on them. Or spray them with acid using equipment they bought from craftsmen spiders......or is this just inside my head?

[TK]

Still say the wasps or bees or whatever would win since they could fly low above the fireants and drop burning objects on them. Or spray them with acid using equipment they bought from craftsmen spiders......or is this just inside my head?

It must be the spirit of X-Wing....


....or maybe the Guinness.