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New Speed Record Set For Wind-Powered Vehicles
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.'"
The downward force on the surface it is sitting has increased, which is the point they are trying to get across.
Stop being a pedantic ass.
Interesting, but totally useless for cars. The wing is way too tall for traffic. But for ships, its a different story. Question is: If it takes a 40 foot high wing to move a 1 ton car, how big of a wing would you need to move a 50,000 ton container ship? The heaviest sailing vessel yet constructed is the Star Clipper: Star Clipper, which is 5000 tons and traditionally rigged with about 50,000 square feet of sail handled by 20 crewman.
This is my sig.
In practice people will hardly ever use your POV that weight is solely the effect of gravity on mass, since it's not that useful.
For most people, weight means "apparent weight". The force that a weighing scale (theoretical or otherwise) would measure if you could put the object on it.
Which in many circumstances will be something like:
mass * acceleration due to gravity - bouyancy due to fluid/air the object is in - the force due to the earth spinning + "other stuff".
"other stuff" could include downforce.
This is more useful since the object could break stuff it goes over if the "practical weight" is too high even if the m*g is less than the limits.
For example, for the speed record on ice attempt, they'll have to figure out whether the ice can take the max "apparent weight".
IMO, weight= m*g is best left for high school physics. People dealing with stuff in the real world will use weight = "apparent weight".
And they're not going to use two words where one word will do.
The "weight = m * g" definition is not very useful.
The only use for that definition I've had is in high school physics exams.
The more useful definition is weight = "apparent weight".
Where weight = the actual force the object would exert on the surface it's on.
And that is not m * g.
It's m * g + downforce - bouyancy - force due to the earth spinning, and all sorts of other stuff.