David Jenkins
|
| posted on 1/8/11 at 11:26 AM |
|
|
Monday puzzle - which way will the little cart go?
Here's something to think about...
Look at this picture:
It shows a little cart made with a couple of bobbins that that can rotate freely. A big wheel sits on top of the bobbins - if you push the cart, the
big wheel rotates in the opposite direction to the bobbins. OK so far?
Now if a ruler is put on top of the big wheel and is pushed to the right, which way will the cart move, and how fast (roughly)?
I'll post the answer in a couple of hours!
|
|
|
|
|
nick205
|
| posted on 1/8/11 at 11:30 AM |
|
|
Depending on the coefficient of friction between the different materials the piece of paper inder the cart should move in the same direction as the
ruler is moving and the cart will stay where it is.
|
|
|
blakep82
|
| posted on 1/8/11 at 11:31 AM |
|
|
does it goes left, roughly 3 times faster than you move the ruler?
no, change my mind, it doesn't move at all! go with that, because the little wheels won't have enough power to them to overcome you
dragging the whole thisng the other way with the ruler
[Edited on 1/8/11 by blakep82]
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
|
|
|
mookaloid
|
| posted on 1/8/11 at 11:36 AM |
|
|
Looks to me like it will move towards the hand
"That thing you're thinking - it wont be that."
|
|
|
richardlee237
|
| posted on 1/8/11 at 11:37 AM |
|
|
it will move to the left and the monkey gets his nose cutoff
Quote Lord Kelvin
“Large increases in cost with questionable increases in performance can be tolerated only in race horses and women.”
Quote Richard Lee
"and cars"
|
|
|
ReMan
|
| posted on 1/8/11 at 11:48 AM |
|
|
Whizz to the lion?
www.plusnine.co.uk
|
|
|
matt_gsxr
|
| posted on 1/8/11 at 11:58 AM |
|
|
Top of wheel moves in same direction as the cart, but way slower.
Pushing on ruler will result in cart moving fast in the direction that ruler is pushed.
Ratio distance move is the same as the ratio bobbin diameter to bobbin-outer minus bobbin-inner diameters.
Go on show us the video
|
|
|
Agriv8
|
| posted on 1/8/11 at 12:04 PM |
|
|
depends if you intend to be on Penn and teller next weekend ?
Best bit of Saturday TV that IMHO
regards
Agriv8
Taller than your average Guy !
Management is like a tree of monkeys. - Those at the top look down and see a tree full of smiling faces. BUT Those at the bottom look up and see a
tree full of a*seholes .............
|
|
|
loggyboy
|
| posted on 1/8/11 at 12:13 PM |
|
|
quote:
Originally posted by blakep82
does it goes left, roughly 3 times faster than you move the ruler?
2nd EDIT: Id go with this answer.
(i just used a cd and a £1 coin to simulate!)
[Edited on 1/8/11 by loggyboy]
[Edited on 1/8/11 by loggyboy]
|
|
|
craig1410
|
| posted on 1/8/11 at 12:14 PM |
|
|
It will move in the same direction as the ruler, to the right and at a faster rate than the ruler is moving in relation to the ground. I had to think
about it for a minute though... 
My thinking goes like this:
1. There is only one external force - that of the ruler applying a force from left to right.
2. This will apply a clockwise force to the bobbins which will in turn apply a counter-clockwise force to the big wheel.
3. The force on the big wheel is working against the external force from the ruler but because of the gearing the force on the bobbins will
"win".
4. Therefore the cart will move right but at several times the speed of the ruler due to the large wheel rotating against the ruler's tangential
direction.
I hope that makes sense...
[Edited on 1/8/2011 by craig1410]
|
|
|
loggyboy
|
| posted on 1/8/11 at 12:16 PM |
|
|
quote:
Originally posted by craig1410
It will move in the same direction as the ruler, to the right and at a faster rate than the ruler is moving in relation to the ground. I had to think
about it for a minute though...
It must move to the left as the secondary large wheel will reverse the travel.
|
|
|
Dingz
|
| posted on 1/8/11 at 12:18 PM |
|
|
Opposite direction to ruler, same speed.
Phoned the local ramblers club today, but the bloke who answered just
went on and on.
|
|
|
Humbug
|
| posted on 1/8/11 at 12:19 PM |
|
|
Assuming that the paper doesn't move the cart must go left if the ruler is pulled to the right.
ETA I think that the ruler will not move in absolute terms (i.e. in relation to the table), but it will move to the right relative to the top of the
wheel at the same speed as the cart moves to the left (relative to the table). Make sense? It does in my mind!
[Edited on 01.08.2011 by Humbug]
|
|
|
David Jenkins
|
| posted on 1/8/11 at 12:30 PM |
|
|
Matt & Craig have got it right!
Video of cart
(the video's a bit stupid, but he does demonstrate how it works - and it looks weird!)
|
|
|
loggyboy
|
| posted on 1/8/11 at 12:30 PM |
|
|
quote:
Originally posted by Humbug
ETA I think that the ruler will not move in absolute terms (i.e. in relation to the table), but it will move to the right relative to the top of the
wheel at the same speed as the cart moves to the left (relative to the table). Make sense? It does in my mind!
If the bobins were the same size of the wheel that would be correct, but the ratios will mean the ruler will move to the right slightly slower than
the cart moved to the left.
|
|
|
loggyboy
|
| posted on 1/8/11 at 12:33 PM |
|
|
quote:
Originally posted by David Jenkins
Matt & Craig have got it right!
Video of cart
(the video's a bit stupid, but he does demonstrate how it works - and it looks weird!)
The ruler IS being pushed to the opposite diection, however the travel of the cart makes it looks like the ruler is being pushed in the same
direction.
|
|
|
craig1410
|
| posted on 1/8/11 at 12:35 PM |
|
|
quote:
Originally posted by loggyboy
quote:
Originally posted by David Jenkins
Matt & Craig have got it right!
Video of cart
(the video's a bit stupid, but he does demonstrate how it works - and it looks weird!)
The ruler IS being pushed to the opposite diection, however the travel of the cart makes it looks like the ruler is being pushed in the same
direction.
Eh? The ruler is being pushed/pulled/whatever from left to right and the cart is moving from left to right. How is that opposite?
Cool video David
[Edited on 1/8/2011 by craig1410]
|
|
|
David Jenkins
|
| posted on 1/8/11 at 12:38 PM |
|
|
quote:
Originally posted by craig1410
quote:
Originally posted by loggyboy
quote:
Originally posted by David Jenkins
Matt & Craig have got it right!
Video of cart
(the video's a bit stupid, but he does demonstrate how it works - and it looks weird!)
The ruler IS being pushed to the opposite diection, however the travel of the cart makes it looks like the ruler is being pushed in the same
direction.
Eh? The ruler is being pushed/pulled/whatever from left to right and the cart is moving from left to right. How is that opposite?
I know what he means - in fact the ruler IS going backwards as far as the big wheel is concerned - the little wheels are driving the cart so fast that
*to the big wheel only* the ruler's going the other way - relative to itself.
|
|
|
loggyboy
|
| posted on 1/8/11 at 12:38 PM |
|
|
quote:
Originally posted by craig1410
Eh? The ruler is being pushed/pulled/whatever from left to right and the cart is moving from left to right. How is that opposite?
Cool video David
[Edited on 1/8/2011 by craig1410]
The rulers direction of movement in relation to the table is nothing to do with the direction in which force is being applied.
|
|
|
craig1410
|
| posted on 1/8/11 at 12:40 PM |
|
|
Okay I think I get you now - I was thinking in terms of motion not force. Sorry. 
|
|
|
Madinventions
|
| posted on 1/8/11 at 12:48 PM |
|
|
The only way that could've been more awesome would be if Johnny Ball did the voice over...
Mojo build diary: http://www.madinventions.co.uk
Solo music project: Syrrenfor http://www.reverbnation.com/syrrenfor
View my band website:
http://www.shadowlight.org.uk
http://www.eastangliankitcars.co.uk/
|
|
|
loggyboy
|
| posted on 1/8/11 at 12:48 PM |
|
|
No need to be sorry!, I love this sort of discussion.
But the wording of the OP is if 'you' move the ruler to right.
Sadly the OP was looking at the optical illiusion and assuming the input of the hand is moving the ruler in the direction of the cart, when in fact
its the cart that is moving the ruler, but the input of force from the hand is in fact pushing the ruler in the opposite direction to that in which it
'appears' to travelling in.
[Edited on 1/8/11 by loggyboy]
[Edited on 1/8/11 by loggyboy]
|
|
|
David Jenkins
|
| posted on 1/8/11 at 01:02 PM |
|
|
This OP disagrees - there is no optical illusion - the ruler IS moving from left to right.
However, as I said earlier, the position of the ruler relative to the big wheel is right to left, which is why the cart does what it does.
I was not confused about what I saw - I was simply impressed by the mechanical aspects of the 'trick' (of course, it is no trick).
|
|
|
loggyboy
|
| posted on 1/8/11 at 01:04 PM |
|
|
quote:
Originally posted by David Jenkins
This OP disagrees - there is no optical illusion - the ruler IS moving from left to right.
However, as I said earlier, the position of the ruler relative to the big wheel is right to left, which is why the cart does what it does.
I was not confused about what I saw - I was simply impressed by the mechanical aspects of the 'trick' (of course, it is no trick).
But you were wrong to say that craig and matt were correct. lol - this is getting complicated!
|
|
|
russbost
|
| posted on 1/8/11 at 01:18 PM |
|
|
If the ruler moves from left to right it must push the large wheel in a clockwise direct - that is NOT what is shown in the video! If the large wheel
was rotating clockwise the cart would move to the left as the bobbins rotate counter clockwise, so I would say there is an optical illusion there, all
to do with the gearing & therefore the perceived motion of the ruler surely! IMHO of course
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
|
NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
|
