New Speed Record Set For Wind-Powered Vehicles 138
Hugh Pickens writes "Richard Jenkins reached 126.1mph in his Greenbird car on the dry plains of Ivanpah Lake in Nevada, setting a new world land speed record for a wind-powered vehicle. 'It's great; it's one of those things that you spend so long trying to do and when it actually happens, it's almost too easy,' says Jenkins. The Greenbird is a carbon fiber composite vehicle that uses wind (and nothing else) for power. The designers describe it as a 'very high performance sailboat,' but one that uses a solid wing, rather than a sail, to generate movement. Due to the shape of the craft, especially at such high speeds, the wings also provide lift; a useful trait for an aircraft, but very hazardous for a car. To compensate for this, the designers have added small wings to 'stick' the car to the ground, in the same way Formula 1 cars do. 'Greenbird weighs 600kg when it's standing still,' says Jenkins. 'But at speed, the effect of the wings make her weigh just over a ton.' Jenkins has also built a wind-powered craft that travels on ice, rather than land. 'Now that we've broken the record, I'm going back on to the ice craft. There's still some debate as to whether traveling on ice or land will be faster.'"
Re:Crap (Score:4, Informative)
Re:Crap (Score:3, Informative)
What I really hate is when TFA is misquoted in the summary, now I see that Jenkins said "tonne" which IS metric. D-oh!
Re:Near light speed? (Score:3, Informative)
Weight and mass are different things. Their usage is correct.
Re:Near light speed? (Score:5, Informative)
Their usage is dead wrong. Weight is the effect of gravity on mass. The vehicle doesn't "weigh" more at speed - the effect of gravity on it hasn't changed. It just generates a down-force from the wing. To say that it weighs more is about as accurate as saying your weight changes as you jump up and down on a scale, or that an airplane weighs less than nothing when it's flying.
Since energy can be converted to mass, they would have to be going at a large percentage of c to actually "weigh" more.
Re:Crap (Score:2, Informative)
Re:Near light speed? (Score:3, Informative)
Right - weight is the effect of gravity on an object of a specific mass. The effect of gravity doesn't suddenly change at speed. The vehicle dos NOT weigh more - gravity's effect on it is constant. What changes is the aerodynamic down-thrust. That doesn't change the vehicle's weight, just as an airplane doesn't suddenly weigh less than nothing when it takes off ... gravity still has the same effect on its mass.
Re:Near light speed? (Score:5, Informative)
Not quite. The downward force when it is stationary is 600gN, the downward force when it is moving is 1000gN. The downward force due to gravity, also known as the weight, in both cases is 600gN. The mass in both cases is 600Kg. Neither the weight, not the mass, change. The mass could only change as a result of things being added to or removed from the vehicle, or as the result of relativistic effects (which are present at the recorded speed, but not significant enough to be measured). The weight could change if the mass changed, or if the vehicle climbed far enough from the centre of the Earth for the inverse-square attraction to be reduced (again, this is unlikely to happen unless it raced up a steep mountain; g varies a bit, but not enough to be worth bothering about, over the surface of the Earth). The downward force can change for a wide variety of reasons, but in this case due to a pressure differential caused by air moving more quickly over the underside of the stabilisers.
Note: In this post, g is used as little-g, the acceleration due to gravity on the surface of Earth, while g is the SI unit gram. This is not quite standard notation; they should both be represented by the same symbol, which is just plain confusing.
Re:Crap (Score:4, Informative)
I should have put a smiley :)
But I do live in the US and so I really wonder why people use "ton" in supposedly metric-standardized countries? I mean, I know that 1000kg is sort-of close to the old 2000lbs, but it is really ambiguous and there is the perfectly good Mega. At the very least, it should be spelled "tonne", right?
Re:Near light speed? (Score:3, Informative)
Since energy can be converted to mass, they would have to be going at a large percentage of c to actually "weigh" more.
That's a non sequitur. Fast moving bodies do not have a higher "effective mass" because some of the energy is converted into mass. It's just an interpretation of the fact that as you approach c it takes more and more energy to accelerate. Another interpretation is that the mass is constant and the momentum does not depend linearly on velocity, but approaches infinity as the velocity approaches c.
Re:Crap (Score:5, Informative)
It's probably for dividing up plots and things. It's nice to be able to evenly divide things into other things. Without the "funny measurements" you end up with lots of fractions, which were much less easy to deal with in the days when a calculator was a person, and most normal people were lucky if they could read.
Note also that an acre is 10 square chains, and 10 acres is a square furlong.
What is a mile? It's a least-common-multiple(ish) of several smaller measurements which happens to be a convenient size for people traveling on foot. The km is also a convenient size for foot travel, but you can only divide it by 2s and 5s without resorting to fractions.
Re:Crap (Score:3, Informative)
1 ton = 1000kg, welcome to the metric system.
Not so fast. Do you mean a British ton [wikipedia.org], US ton [wikipedia.org], or metric ton(ne)? [wikipedia.org] And, for more confusion, see that there is also a French ton [st-and.ac.uk].
Okay. I should stop being facetious and get my 7 hours of sleep (relative to current Earth's rotation period - has to be said, because it is slowing down).
Re:Crap (Score:2, Informative)
A ton (known as a "long ton" in the US) is 2240lb i.e. 1016kg.
In Commonwealth countries, to make things easier to calculate, a ton is now generally taken as 1000kg.
In America, to make things easier to calculate, a ton is now generally taken as 2000lb i.e. 907kg.
The spelling is now largely irrelevant since nobody really remembers the old system that well. All official or scientific measurements are in kilograms anyway, ton and tonne are both just colloquial, it never needs to be precisely disambiguated in the contexts where it is used. For what it's worth, the metric approximation is far closer anyway.
Re:Crap (Score:3, Informative)
it's the weight of 1 cubic metre of water.
Re:Crap (Score:3, Informative)
What is a mile?
The word "mile" comes from mille, latin for thousand (just like the milli- prefix). A mile is 1000 paces of the Roman legions (a pace is 2 steps). At least that is the basis for the general distance- the exact amount depended on who decided to define what exactly it meant (such as the English defining it as the above post points out).