jumping around on busses

John Player

hey all,

firstly sorry if this is in the wrong forum didnt know where else to put it!

have a question thats been bugging me
for years, would really appreciate if someome could answer it for me.

if im on a fast moving bus and i jump in the air, how comes i dont go flying
out the back window but i land in the exact same spot that i jumped from?


thanks in advance

limpdd

You might be better off asking in the science forum, they know everything

Dr. Dre

Well, don't forget that you are moving at the same speed as the bus in the same direction so I'm sure that plays some part in it.
But Limp is right, head over to the science forum.


EDIT: Oh and here is somewhere that may help with all those nagging questions in your head, www.howstuffworks.com
I especially like their topic on Einstein's relativity theories, 'tis a good show !

dod

Assuming that the bus is moving forward, you have a forward velocity equal to that of the bus. Due to the principle of conservation of momentum, the forward momentum must be conserved unless an extraneous force acts upon the object. When you jump up, you maintain your forward momentum whilst briefly in the air and come back down in the same place as you jumped from.

Silent Bob

If the bus was accelerating very fast (this will never happen:)) then you would find that you move backwards a bit (it's the same reason that you get pressed into the back of a seat when something accelerates in a forward direction).

scojones

if there was no windscreen you would find yourself going backwards, same with a piece of ash floating in your car that's doing 120mph.

Mark

Huh. I had never thought of this before but now that I read it I was totally beffugled as to the science of it.

Well WHILE I'm here and we're discussing this sort of thing, here's something that's bothered me on and off for months.

Assume you're a rich bastard and you bought one of dem dere eckersize bikes. You know the sort, you cycle like mad without the bike moving.

Right so what if you had your feet and legs firmly, and I mean so firmly as to entail loss of movement control, strapped into the cycling position with yer feet in the straps.

So then if the bike was automated to run at high speed (alá a treadmill) with said legs and feet strapped in-

Would this simulate the same effect as if you were manually pedelling? After all, your legs are still going through the motions...?

I know sweet fig all about exercise (hence the laziness inherent in the question) and I'm fairly sure it wouldn't work because someone would have marketed it by now, by WHY wouldn't it work?

Goe Science! *waves small flag*

Sir Digby Chicken Caesar

because you're not using the muscles, and forcing them to do the work.. your legs are just being pulled around the place like crazy
?

Capt'n Midnight

and you are standing up stairs - then you'd probably go out through the front windows

have a look at the Jackie Chan film Police Story - it's shows two lads doing just that - followed by an back fip and landing on the road (both were professional stuntmen and both cracked thier skulls..)


====================================

Energy - it takes about 3,600Kcal to loose one pound
(someone please translate into KJ/Kg)

So if you peddle harder and faster you burn lots more weight then freewheeling.

I saw something where leg muscles could actually generate ATP from movement - but I'd doubt it would be enough to live on...

Victor

The bus is doing say 50kmh, the air in the bus is doing 50kmh, as you jump, air resistance prevents you from moving substantially.

Now do the same standing on the roof of the bus (not recommended) and you will notice that the air isn't doing 50kmh (its still) air resistance will try to being you from 50kmh to stop. If you jumped vertically up at the back of the bus roof, you would fall off and kill yourself (most likely).

Silent Bob

Mark, you would get benefit from such an exercise. You would not get the same amount of benefit as you would if you actually did it yourself though.

This kind of manipulation is a technique physios use to stop muscles atrophying in people who can't use them temporarily.

Boston

to answer the original question. in science there is no such thing as velocity, only relative velocity. your velocity relative to the buses is zero therefore you come straight down.

Capt'n Midnight

slendertone or whatever - wireyour self up -whack up the voltage and your muscles will do the rest - and they will burn off some energy.. [Warning - electricity can kill you]

Hmmm... if you could synchronise the inpulses between both legs you could sit on an excersise bike - wired up to a generator - you'd save a fortune in heating and ESB bills and the added bonus of being able to eat as many cream buns as you desire

the better way of stimulating leg muscles on an excersise bike it the way the tried it on kids in the US - when you stop peddling the TV turns off...

Victor

Originally posted by Capt'n Midnight
slendertone or whatever - wireyour self up -whack up the voltage and your muscles will do the rest - and they will burn off some energy..

Serious doubts have been raised about such products, by among others the FDA.

PrecariousNuts

Imagine falling asleep and leaving one of those things on overnight

amen

boston not quote true
due to gravity and earths rotation you won't come back exactly where u started but since he is only jumping a little bit and hes very large then its close enough

as for Victor

The bus is doing say 50kmh, the air in the bus is doing 50kmh, as you jump, air resistance prevents you from moving substantially.

not really true
to someone ourside the buss the air might be at 50Khm but to someone in sides its basically still.

Victor

Originally posted by amen
to someone ourside the buss the air might be at 50Khm but to someone in sides its basically still.

Not just to "someone" - but to everyone outside the bus the air in the bus is doing 50kmh - Boston's point.