Which ones (if any) of these sentences are true?

[RogerS]

a jet or prop would be thrusting the aircraft forward, its going to move forward and colide with the giant treadmill, the treadmill is in a static position

The jet might be thrusting the plane forward but the tread of the treadmill is going backwards underneath so the plane will remain stationary.

 

[dannykaye]

I'm not sure that he will see anything if it is a perfect mirror. By perfect, any light will be reflected back down it's own path and to the torch. By perfect there will be no internal light scatter inside the mirror so there would be no stray photons coming out at other angles to then bounce off other parts of the mirror. Am I right?

except it is not a flat mirror and the torch might not be exactly in the centre

 

[barkwindjammer]

a jet or prop would be thrusting the aircraft forward, its going to move forward and colide with the giant treadmill, the treadmill is in a static position

The jet might be thrusting the plane forward but the tread of the treadmill is going backwards underneath so the plane will remain stationary.

This would equate if it were the wheels of the plane creating forward motion

 

[Jacob]

Eat your peas up and get back to work :?

Impossible - elastic peas bounce all over the place.

Re plane - if the treadmill is going at take-off speed then the plane (if fixed, PS to the treadmill) is being forced through the air at take-off speed and hence will take off, at a tangent, the instant it is released (horizontally), even without the engines fired up, but without which it would come down again quickly.

PS assuming the treadmill is sending the plane forwards! Or can they fly backwards?

 

[Racers]

Hi,

Mythbusters did the conveyor belt /plane with a real plane and it took off, the propeller pushes against the air not the ground/treadmill.

http://www.youtube.com/watch?v=OyUpDQ-fpTc

Pete

 

[barkwindjammer]

If a plane is 'fixed' then it wont take off whether or not a giant treadmill is used to 'spin the wheels', aircraft are propelled forward by thrusting air backwards and not by propelling them forward by the wheels, it is true that the wings are what create the lift, so to sum up

A: a fixed aircraft wont move forward let alone up

B: the wheels are 'free wheels' and provide no forward movement

C: air thrusted backwards provides the forward force

D: rubber peas are tricky to eat without the aid of adhesive cutlery

so, the question was 'will the plane take off ?'
answer no

'What will the plane do'?
answer colide with the rotating treadmill, as its forced forward and the treadmill isn't

Q: does anyone know of a foodsafe adhesive? :wink:

 

[Jacob]

Heres another puzzler for you,

If I stand facing an oncoming train, and when it gets into range I fire a pea shooter at it, will the train stop?

My case is that the pea will bounce off, doing a complete change of direction 180degrees, as it changes direction, there must be a point in time where it is stationary, and not going in either direction, you must therefore deduce that the pea stops, when the pea is stationary it will be in contact with the front of the train, therefore it follows that if the pea is stationary and in contact with the train, the train must also be stationary. :roll:

This reasoning assumes that both peas and trains are perfectly inelastic, which is (obviously) not the case.

BugBear

Makes no (difference). Except that if inelastic, not all particles of the train and/or pea are traveling at the same time with the same speed and direction.

That is so wrong. .....

No it's right. The difference is that not the whole pea (or the whole train) is acted upon (or reacts) simultaneously. There'd be a pressure wave.

 

[RogerS]

But if the plane is thrust forward by virtue of the propeller then that will make the wheels roll but if the treadmill moves backwards at the same rate then the plane will remain stationary. If it remains stationary than it will have no airflow and hence no lift.

 

[RogerS]

Heres another puzzler for you,

If I stand facing an oncoming train, and when it gets into range I fire a pea shooter at it, will the train stop?

My case is that the pea will bounce off, doing a complete change of direction 180degrees, as it changes direction, there must be a point in time where it is stationary, and not going in either direction, you must therefore deduce that the pea stops, when the pea is stationary it will be in contact with the front of the train, therefore it follows that if the pea is stationary and in contact with the train, the train must also be stationary. :roll:

This reasoning assumes that both peas and trains are perfectly inelastic, which is (obviously) not the case.

BugBear

Makes no (difference). Except that if inelastic, not all particles of the train and/or pea are traveling at the same time with the same speed and direction.

That is so wrong. .....

No it's right. The difference is that not the whole pea (or the whole train) is acted upon (or reacts) simultaneously. There'd be a pressure wave.

You can only have a pressure wave if the object is elastic.

 

[dannykaye]

But if the plane is thrust forward by virtue of the propeller then that will make the wheels roll but if the treadmill moves backwards at the same rate then the plane will remain stationary. If it remains stationary than it will have no airflow and hence no lift.

the propeller will move the plane forward, if the treadmill is still the wheels will revolve at, say, x meters per, if the treadmill is moving at x meters per, in one direction the wheels will not revolve in the other they will tevolve at 2x. the motion of the plane and that of the wheels coupled to the treadmill are not connected as they have what we might call a loose joint in the system, ie the axle of the wheels

 

[Jacob]

Heres another puzzler for you,

If I stand facing an oncoming train, and when it gets into range I fire a pea shooter at it, will the train stop?

My case is that the pea will bounce off, doing a complete change of direction 180degrees, as it changes direction, there must be a point in time where it is stationary, and not going in either direction, you must therefore deduce that the pea stops, when the pea is stationary it will be in contact with the front of the train, therefore it follows that if the pea is stationary and in contact with the train, the train must also be stationary. :roll:

This reasoning assumes that both peas and trains are perfectly inelastic, which is (obviously) not the case.

BugBear

Makes no (difference). Except that if inelastic, not all particles of the train and/or pea are traveling at the same time with the same speed and direction.

That is so wrong. .....

No it's right. The difference is that not the whole pea (or the whole train) is acted upon (or reacts) simultaneously. There'd be a pressure wave.

You can only have a pressure wave if the object is elastic.

Deliberate error - I meant elastic when I said inelastic.

 

[RogerS]

Thanks, Danny, I get it now.

 

[llangatwgnedd]

Get a life you daft bats.

 

[Jake]

Good to see a topic wot sorts the wheat from the chaff.

 

[barkwindjammer]

Good to see a topic wot sorts the wheat from the chaff.

as peeps that used to use CB radio would say
roger !

 

[Jacob]

It's like being back at school (3rd form). We had a term long argument about who was the greatest guitarist in the world - Julian Bream, Hank Marvin or Duane Eddy.

 

[Sportique]

It seems to me that the pea will bounce on the out-going tide, this will cause the train to go into reverse colliding with the treadmill and forcing the plane to vanish up its own whatsit.

I think the mirror is a red herring and astronauts cannot eat herrings.

Anyone read Isaac Asimov writings about the moon (The Tragedy of ...) ?

Dave

 

[Benchwayze]

Heres another puzzler for you,

If I stand facing an oncoming train, and when it gets into range I fire a pea shooter at it, will the train stop?

My case is that the pea will bounce off, doing a complete change of direction 180degrees, as it changes direction, there must be a point in time where it is stationary, and not going in either direction, you must therefore deduce that the pea stops, when the pea is stationary it will be in contact with the front of the train, therefore it follows that if the pea is stationary and in contact with the train, the train must also be stationary. :roll:

As any camera can prove with fast enough film! :lol: :lol: :lol:

 

[Benchwayze]

a) True

b) True

c) two light beams travelling towards each other an observer travelling with one can measure the passing speed of the other and it will be c not 2c

d) difficult because it is shorter dur to dilation, you could never stop it tho

e) True

here's one that I can never satisfy myself about, an astronaut is floating in space at the centre of a perfect spherical mirror. he turns on a flashlight, what does he see

I'm not sure that he will see anything if it is a perfect mirror. By perfect, any light will be reflected back down it's own path and to the torch. By perfect there will be no internal light scatter inside the mirror so there would be no stray photons coming out at other angles to then bounce off other parts of the mirror. Am I right?

He would see the effects of spherical abberation. A mirror whose surface is part of a perfect sphere gives a distorted image at its focus. Which is why a telescope mirror is figured to a parabolic curve to bring the reflected rays to a predetermined focus.

I think! :roll:

 

[dannykaye]

It's like being back at school (3rd form). We had a term long argument about who was the greatest guitarist in the world - Julian Bream, Hank Marvin or Duane Eddy.

Have twangy guitar almost has it but my vote goes to ragtime cowboy jew