The Naked Scientists

The Naked Scientists Forum

Author Topic: Going forwards while going backwards  (Read 6917 times)

Offline dentstudent

  • Neilep Level Member
  • ******
  • Posts: 3146
  • FOGger to the unsuspecting
    • View Profile
Going forwards while going backwards
« on: 12/07/2007 10:49:43 »
Did you know that there is always a part of a standard passenger train that is going backwards,as the train travels forwards. In fact, the faster, forwards it travel, the faster this part goes backwards!



(I really hope this is true, otherwise I'm going to look like a right small flighty creature)


 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
Going forwards while going backwards
« Reply #1 on: 12/07/2007 11:47:12 »
 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
Going forwards while going backwards
« Reply #2 on: 12/07/2007 12:21:05 »
Did you know that there is always a part of a standard passenger train that is going backwards,as the train travels forwards. In fact, the faster, forwards it travel, the faster this part goes backwards!



(I really hope this is true, otherwise I'm going to look like a right small flighty creature)

OK Stuart which Part goes backwards!! Where is The Mad MAN our resident train expert! LOL.. Come on Stuart give it up! Which part! LOL
 

Offline dentstudent

  • Neilep Level Member
  • ******
  • Posts: 3146
  • FOGger to the unsuspecting
    • View Profile
Going forwards while going backwards
« Reply #3 on: 12/07/2007 12:23:13 »
I'll give you a hint - what do you find up your nose?
 

paul.fr

  • Guest
Going forwards while going backwards
« Reply #4 on: 12/07/2007 12:23:58 »
I'll give you a hint - what do you find up your nose?

fingers!
 

paul.fr

  • Guest
Going forwards while going backwards
« Reply #5 on: 12/07/2007 12:25:51 »
 

Offline dentstudent

  • Neilep Level Member
  • ******
  • Posts: 3146
  • FOGger to the unsuspecting
    • View Profile
Going forwards while going backwards
« Reply #6 on: 12/07/2007 12:27:06 »
Indeed - so.......?

(in a "therefore" kind of way, not a "what" kind.....this posting lark is full of pitfalls!)
 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
Going forwards while going backwards
« Reply #7 on: 12/07/2007 12:29:20 »
I'll give you a hint - what do you find up your nose?
LOL LOL!!!

I'll give you a hint - what do you find up your nose?

fingers!
LOL Thanks Paul I was going to say it but You saved me !!! AH Chivalry is not dead! LOL .. I still don't know looking at this picture!
 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
Going forwards while going backwards
« Reply #8 on: 12/07/2007 12:30:31 »
Stuart is the riddler today I am lost!
 

paul.fr

  • Guest
Going forwards while going backwards
« Reply #9 on: 12/07/2007 12:30:37 »
LOL Thanks Paul I was going to say it but You saved me !!! AH Chivalry is not dead! LOL .. I still don't know looking at this picture!

It's a picture of a train bogey.
 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
Going forwards while going backwards
« Reply #10 on: 12/07/2007 12:33:06 »
  LOL...LOL OK, play on words I get the train bogey as Boogie, But now can you explain or illustrate which part that is on the underneath of this train?
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
Going forwards while going backwards
« Reply #11 on: 12/07/2007 12:41:56 »
I'll give you a hint - what do you find up your nose?

fingers!

 

Offline dentstudent

  • Neilep Level Member
  • ******
  • Posts: 3146
  • FOGger to the unsuspecting
    • View Profile
Going forwards while going backwards
« Reply #12 on: 12/07/2007 13:00:52 »
So, bogies is ALONG THE RIGHT LINE......
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
Going forwards while going backwards
« Reply #13 on: 12/07/2007 13:10:05 »
The bottom half of the wheels?
 

Offline dentstudent

  • Neilep Level Member
  • ******
  • Posts: 3146
  • FOGger to the unsuspecting
    • View Profile
Going forwards while going backwards
« Reply #14 on: 12/07/2007 13:13:49 »
Getting closer......you're on the right track, maybe you should look under it?
 

paul.fr

  • Guest
Going forwards while going backwards
« Reply #15 on: 12/07/2007 13:17:26 »
Getting closer......you're on the right track, maybe you should look under it?

ahh, now i get it.
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
Going forwards while going backwards
« Reply #16 on: 12/07/2007 13:20:16 »
A squashed hedgehog?
 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
Going forwards while going backwards
« Reply #17 on: 12/07/2007 13:37:27 »
Well I am completely lost! HEE HEE HEE!
 

Offline dentstudent

  • Neilep Level Member
  • ******
  • Posts: 3146
  • FOGger to the unsuspecting
    • View Profile
Going forwards while going backwards
« Reply #18 on: 12/07/2007 13:37:58 »
OK, here is a diagramatic explanation of what is occuring....

The track is represented by the horizontal line. The train wheel has one part that goes onto the track, and a larger part that goes behind the track. If you mark a point on the track sitting part of the wheel, when it rotates, it describes a series of curves that touch the track. This is where the wheel is momentarily motionless during its rotation. The point on the larger part of the wheel behind the track describes a larger curve, and becuase it is larger than the track part, it rotates around this point, and therefore has a backward movement for all points below the track.

 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
Going forwards while going backwards
« Reply #19 on: 12/07/2007 14:17:39 »
HEE HEE HEE! LOL Nice explanation Good diagram,... I don't get it! LOL It makes no sense to me I would have to see it work! LOL I will read it several more times to try to understand!
 

Offline dentstudent

  • Neilep Level Member
  • ******
  • Posts: 3146
  • FOGger to the unsuspecting
    • View Profile
Going forwards while going backwards
« Reply #20 on: 12/07/2007 14:20:40 »
Maybe stick 2 different sized coins together, then run the smaller one along the table edge. That might help......
 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
Going forwards while going backwards
« Reply #21 on: 12/07/2007 14:44:36 »
Wouldn't that leave the outer bigger coin stationary or does the inner wheel turn and propel the outer one?
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
Going forwards while going backwards
« Reply #22 on: 12/07/2007 15:12:27 »
Your diagram proves I was right. Any point on the wheel lower than halfway up is moving backwards.  [^]
 

Offline dentstudent

  • Neilep Level Member
  • ******
  • Posts: 3146
  • FOGger to the unsuspecting
    • View Profile
Going forwards while going backwards
« Reply #23 on: 12/07/2007 15:23:39 »
Your diagram proves I was right. Any point on the wheel lower than halfway up is moving backwards.  [^]

No, I don't think so. No point on the outer rim is moving backwards until it goes below the track. Above the track, the point on the outer rim is still moving forwards until it becomes level with the track.

Perhaps I'm not explaining it well enough. If the wheel was stationary, and you span it around the axle, then you are right - once the outer rim goes below then it does start moving backwards. This would happen for all of the wheel, not just the part that drops below the track. But its not stationary. On the diagram, it's only the little loop at the bottom that exhibits the backwards motion.
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
Going forwards while going backwards
« Reply #24 on: 12/07/2007 15:28:50 »
Your diagram proves I was right. Any point on the wheel lower than halfway up is moving backwards.  [^]

No, I don't think so. No point on the outer rim is moving backwards until it goes below the track. Above the track, the point on the outer rim is still moving forwards until it becomes level with the track.

Perhaps I'm not explaining it well enough. If the wheel was stationary, and you span it around the axle, then you are right - once the outer rim goes below then it does start moving backwards. This would happen for all of the wheel, not just the part that drops below the track. But its not stationary. On the diagram, it's only the little loop at the bottom that exhibits the backwards motion.

With proper trains that may be true; but not with British trains. A little bit of ice or leaves on the track and their wheels spin.

 [^]
 

The Naked Scientists Forum

Going forwards while going backwards
« Reply #24 on: 12/07/2007 15:28:50 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums
 
Login
Login with username, password and session length