Question of the day

[Doohickey]

Is that professionally in England? I think it was something like Albert Johansson for Leeds.

 

[BennyD]

Walter Tull was one of the first and he was also one of the first black army officers. He was the first black army officer to command white troops in battle and was killed in 1917. He was never found. IIRC, the first black player was a guy called Warton or Wharton and he played for PNE. I seem to remember this because Warton is a town near Preston and was part of my 'area' when I was a scuffer.

 

[daverichardson]

Robertson's jam Golly

 

[spkennyuk]

Wharton. Played for Stockport County and other clubs in the early 1900's. I don't know his first name.

 

[davy83]

You are really not used to being wrong are you, i am going to leave it now ,as you are not really thinking here.

Conservation of energy and momentum.

The kinetic energy that the fly has is extremely small - mass of .000001 kg, it's doing 5mph (2.24m/s) northbound, and therefore has a KE of say 0.000025 Joules.

The KE of the train is a bit higher... Say around 100tons mass, then the KE is 101250000 Joules.

The train has to overcome the KE of the fly, and reverse it's velocity vector, and accelerate it up to 100mph southbound. The energy loss to the train is imperceptible... Under standard Newtonian laws, the train CANNOT have an impulse delivered to it to bring its velocity to zero for an instant. Not unless an equal or even large impulse is delivered, and boy will that smart...

 

[drewf]

You are really not used to being wrong are you, i am going to leave it now ,as you are not really thinking here.

That's a bit harsh Davy! I believe I am really thinking here, not spouting pub-nonsense read from the back of a crisp packet. Have a look at Zeno's paradoxes, which work along the same lines as your postulation - basically saying that a faster object can never catch a slower object, as the slower object has always moved forward a bit every time that half the distance between the two has been covered. It's b0ll0x, and demonstrably so. I'll leave you to believe what you like though

 

[davy83]

pub nonsense, mmmm.... i suspect we are picking over details here. There is a simple principle here which seems obvious to me, and clearly not to you. It is obvious to even pub nonsense that train does not actually stop. it is also clearly true that the actual nub of this question relates to times and distances that are so small to be ignored in any sensible engineering consideration, but it is also true that the two objects share a moment when their velocity is zero, regardless of how short a moment that is, and i do not agree that because it is very short it does not happen. you seem to want to dismiss this event, because it is easier to deal with.

 

[daverichardson]

come on chaps lets forget flies and trains
Whose turn is it for the next mind bender

 

[BennyD]

If a car doing 100mph going north hits a wasp doing 5mph going south, does the car stop at impact? And if it does is it too cheap?

 

[spkennyuk]

If a car doing 100mph going north hits a wasp doing 5mph going south, does the car stop at impact? And if it does is it too cheap?

Only you Benny. How big is the wasp and how big is the car ?

While we are waiting for the answer being given on the football player. I shall set another question for you all.

 

[drewf]

pub nonsense, mmmm.... i suspect we are picking over details here. There is a simple principle here which seems obvious to me, and clearly not to you. It is obvious to even pub nonsense that train does not actually stop. it is also clearly true that the actual nub of this question relates to times and distances that are so small to be ignored in any sensible engineering consideration, but it is also true that the two objects share a moment when their velocity is zero, regardless of how short a moment that is, and i do not agree that because it is very short it does not happen. you seem to want to dismiss this event, because it is easier to deal with.

It's a very well known problem, and the genuine answer from minds far greater than my feeble effort, is that the train doesn't stop, not even for the smallest instant. It doesn't share a moment with the fly where its velocity is zero.

The problem is posed to attempt to confuse people by referring to Zeno's paradox and similar ancient world thoughts, stemming from a time before calculus was understood. Now, if you don't or won't understand it, that's fair enough. But please stop telling me I'm ignoring a problem to suggest it doesn't happen, because it's easier to deal with!

Let me turn it round - can you prove that the two bodies have a velocity of zero? Not just state it, but prove it? It's merely a question of physics, so should be straightforward to work out.

 

[drewf]

If a car doing 100mph going north hits a wasp doing 5mph going south, does the car stop at impact? And if it does is it too cheap?

You can't trust wasps.

 

[spkennyuk]

Based on all recorded global airtime data there are two songs that appear in the top 10 most played tunes almost every year. The two songs are connected by one word. Both songs were were in the UK top 5. The word isn't in the titles of the songs.

What is the word ? what are the songs and artist or group that sang them ? What does the word mean ?


Airtime data used includes everything from radio, television, jukebox and hotel, shop or lift background music.

There are only three recorded songs that I know of containing this word.

 

[drewf]

'Grease' is the word, isn't it?

 

[BennyD]

You can't trust wasps.

You can't. The little black and yellow bastards.

Wow, I didn't expect that! Has the filter been switched off?

 

[spkennyuk]

'Grease' is the word, isn't it?

Lol, Not even close.

 

[drewf]

You can't. The little black and yellow bastards.

Wow, I didn't expect that! Has the filter been switched off?

**** knows.

Apparently not...

 

[zagatoes30]

Based on all recorded global airtime data there are two songs that appear in the top 10 most played tunes almost every year. The two songs are connected by one word. Both songs were were in the UK top 5. The word isn't in the titles of the songs.

What is the word ? what are the songs and artist or group that sang them ? What does the word mean ?

No idea but it has got me head scratching

 

[spkennyuk]

No idea but it has got me head scratching

I shall make it a little easier. Both songs were UK number 1's

 

[davy83]

Ok let me try to explain this well know fact to you as best i can

An object cannot simply change from on velocity to another instantaneously. We use Einsteins Force = mass X Acceleration to work this out. So as you apply force to an object to alter its velocity there is a finite level of acceleration that can be generated bounded by the mass of the object and the force applied to it.

In this extreme case the force available is very large and the mass of the fly is very small so the acceleration achievable is very high but not infinite.

If the acceleration is finite, then the change in velocity is also finite, so therefore there is a velocity profile starting with the steady state velocity before the impact and ending with the steady state velocity after the impact. If you plot the velocity of the two objects both before and after the impact there will be a finite length of time where the two objects (after contact) are at zero velocity because the smaller object started at a negative velocity relative to the train and changes to a positive velocity.

The puzzle is more difficult to accept because every one knows that fly's hit trains and cars all the time and have no effect. If the question had been a house brick then the mass would be larger and the force larger, causing the surface of the train to experience much higher forces to create the change in velocity of the brick and so damage occurs.

It is not however true to assume that the force to alter the velocity of a fly is zero, it will be very small and the force experienced by the small area on skin of the train to create the acceleration will be so small that it will likely allow the trains skin to flex and return to an undamaged state, but it must exert force on the fly (or the mass of the fly, since it will change a bit in this process) and will be at zero velocity for perhaps a few nanoseconds or less, not sure, but it is inherently true and this is evident both from the know law that F=ma and also intuitively true if you consider larger objects, like birds or house bricks.

I was told this puzzle by an eminent university professor who used it to make his students think clearly about things, so its not my questions sir, and as far as I am aware this is a known fact and not an act of belief on my part.

It's a very well known problem, and the genuine answer from minds far greater than my feeble effort, is that the train doesn't stop, not even for the smallest instant. It doesn't share a moment with the fly where its velocity is zero.

The problem is posed to attempt to confuse people by referring to Zeno's paradox and similar ancient world thoughts, stemming from a time before calculus was understood. Now, if you don't or won't understand it, that's fair enough. But please stop telling me I'm ignoring a problem to suggest it doesn't happen, because it's easier to deal with!

Let me turn it round - can you prove that the two bodies have a velocity of zero? Not just state it, but prove it? It's merely a question of physics, so should be straightforward to work out.