MegaSack DRAW - This year's winner is user - rgwb
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so , the ususal i got 60mpg outta my 1.9tdi engine thread is happening but how far could man travel.
This is the scene
Fairly fit person,mid 20's, a banked circuit with a time trial bike
Wakes up in the morning, we give him 1 gallon of juice to drink. How far would someone get before dying?
Thus the test......... would man travel further on 1 gallon of juice than a car would with 1 gallon of fuel?
But he's not travelling on 1 gallon of juice. He's travelling on the glycogen in his muscles & his fat reserves & other nutritional stuff I don't understand.
A diesel car will go further on a gallon of diesel than a person would go on a gallon of diesel - fact.
What a silly question! 🙂
Unless you mean how far can a person travel on the calories obtained from said juice? Further than 60 miles in any case I imagine
In terms of physiological efficiency, a human body doesn't compare very well against a car. There's lot of energy overheads in things like powering the brain etc. Kind of like having an already inefficient car and then putting on the air con and a huge ICE system
Don't know any figures off top of my head
easy enough to work out with time. Work out the energu content of diesel, work out the energy content of orange juice and use the efficiency rating of a human and a car and bob's your uncle. The human would win though by my guess.
In terms of physiological efficiency, a human body doesn't compare very well against a car. There's lot of energy overheads in things like powering the brain etc. Kind of like having an already inefficient car and then putting on the air con and a huge ICE system
Are you sure about that?
According to that link I posted. a person would be able to do 900+ miles on the 31,000 calories in a (us)gallon of fuel, compared to 30 for an average car. Methinks the body has it....
Person = ~70 kgs. Car = ~1.5 tons. We're more efficient.
how far can a person go - man on man content
31,000 calories in a (us)gallon
Think thats wrong, a gallon, roughly 8 pints, you wouldn't get anywhere near that amount of calories
Humans are about 25% efficient when cycling I believe. This compares fairly well with a petrol engine at 25% but not with a diesel at around 35%. Although I think those figures refer to the engine itself not the whole car whereas the human figure I think refers to an actual cyclist - air resistance etc should make the car worse than the human I'd say. Although are we talking the car travelling the same speed as the cyclist?
That howstuffworks article seems to disagree with me tho - far enough, but I dispute their figures a bit. You can't power a person purely on vegetable oil, you also need carbs which would skew their average a bit. Plus the person needs quite a bit of that energy just to stay alive - a person in bed still uses energy. Then again the discrepancy could be accounted for by the air resistance etc of the car itself hmm...
Raddogair - oil has maybe 750cal/100g IIRC, which is 7,500 per litre or about 30k for 4 litres - not far wrong.
[url= http://www.exploratorium.edu/cycling/humanpower1.html ]cyclist wins[/url] 🙂
Humans are about 25% efficient when cycling I believe. This compares fairly well with a petrol engine at 25% but not with a diesel at around 35%. Although I think those figures refer to the engine itself not the whole car whereas the human figure I think refers to an actual cyclist - air resistance etc should make the car worse than the human I'd say. Although are we talking the car travelling the same speed as the cyclist?
Surely even if these efficiency figures are right, those are just energy-in vs energy out efficiencies, which don't mean anything in this situation - the car weighs 10-15 times as much as a single person plus a bike, meaning that to take a person from A to B, the car has to use 10 times as much energy, making your 10% difference in efficiency a drop in the ocean compared to the massive weight difference.
Joe
How about if the cyclist is going camping for the weekend with his girlfriend? How well does he do with a tent, sleeping bags, couple of chairs, clothes, cooker, cool box full of food, lantern, airbed, ipod & speakers, plates/cutlery/pots & pans, table, extra bike for his girlfriend.
Oh and he's got to pick her up from work, then cycle 100 miles in a couple of hours or it'll be too dark to pitch the tent.
😉
I was treating the question more theoretically. Raw efficiency values are very comparable I believe not certain though and the links above certainly cast doubt.
Not purely to do with weight either. JoeMarshall, you're comment about it taking 10x as much energy if it weighs 10 times as much is only true during acceleration in the inertial frame, and if the car is going up a constant incline. Once the car/rider is up to speed, the dominant forces are due to rolling friction and air resistance which are size/mass dependent but not linearly related. In terms of useful work we get in terms of movement for calories in I was always under the impression that we were just as rubbish as cars and other combustion type processes. We do have some natty side effects from the use of the energy, conciousness, body heat, sight etc. but that's not what was asked originally.
Can i go home now? 😕
I worked this out once when i was bored. Think i based it on using 700 calories per hour, and cycling at 20 mph and using the number of calories in a gallon of petrol.
I got around 700mpg for a person cycling i think.
i'm pretty sure the best 'car' gets something like 3000mpg in those eco marathon things.
I read somewhere that 1 barrel of oil will do the same 'work' (technical physics term) as 25 men in 12 years. Or something daft like that. The point it was getting at was slightly different, in that when oil runs out we're ****ed if we think we're having an easy life.
I read somewhere that 1 barrel of oil will do the same 'work' (technical physics term) as 25 men in 12 years. Or something daft like that. The point it was getting at was slightly different, in that when oil runs out we're ****ed if we think we're having an easy life.
Always the scientist
Thats what the Sc stands for in MSc 😉