Posted on 11/26/2002 4:49:49 PM PST by topher
No, YOU are the one missing the point.
How can it be "nonsensical" to refer to a mass of 14 tons, and be sensible to refer to a mass of 100 Kg as you did?
If it had a mass of 14 tons on the surface of the Earth, and assuming the ride up didn't lose anything, then it still has a mass of 14 tons in orbit. It lost weight.
And if you read the quote the poster is referring to, the reporter actually used the term MASS, not weight.
You still haven't answered the question:
Why do you say they said "weight", when the quote you gave says "mass" ???
No space is not a weightless environment. There is an appearance of weightlessness since the shuttle, astronauts, girter and iss are all falling together. If they were weightless they would not orbit but would continue in a straight line leaving earth. The pull of gravity bends their course to produce an orbit.
Or any other object. Space is described as a microgravity environment, not a weightless one.
If you drop an apple on Earth, it falls at 1g. If an astronaut on the Space Station drops an apple, it falls too; it just doesn't look like it's falling. That's because they're all falling together; the apple, the astronaut, and the Station. But they're not falling towards the earth, they're falling around it. But since they're all falling at the same rate, objects inside of the Station appear to float in a state we call zero gravity (0g), or more accurately microgravity (1x10-6 g.)
They used "tons" for measurement -- a measurement of "weight". If they used "kilograms" or "metric tons", they would be giving the "mass" of the object, not the weight.
On lift off, the weight of the girder in question, for example weighed more than on the ground because it was subject to about a couple of G's of pressure on liftoff.
The article is filled with errors that could have been corrected with simple sentances like:
"On earth the girder weighed 14 tons, but in outer space, it weighs only a small fraction of that, enabling the shuttle's robot arm to lift very heavy 'masses' in orbit that it could not on earth. Just as the astronauts 'seem' to float in outer space, objects weigh significantly less in orbit."
It could have been correct and informative.
If it had a mass of 14 tons on the surface of the Earth, and assuming the ride up didn't lose anything, then it still has a mass of 14 tons in orbit. It lost weight.
And if you read the quote the poster is referring to, the reporter actually used the term MASS, not weight. The unit "tons" and "pounds" refer to weights. The term kilograms refer to mass. The object has the same "mass" on earth as it does in space, which is measured in terms of "metric tons" or "kilograms". The counterpart for pounds (weight) that is the unit of mass is "slugs".
Basically, it has a WEIGHT of 14 tons on earth, and it has a mass of so many "metric tons". The constant is the measurement of "mass", not weight. If the article used measurements in terms of "mass", and not "weight", we would not be arguing about the fact they used "tons" to mean "mass" when "English tons" refer to the "weight" of an object, not "mass".
Students reading these articles will get confused when they have to work on problems of "mass" and "weight", as they will been exposed to improper use of the two terms.
Basically, since they use "weight measurements" to describe "mass", it is very confusing.
Here are some links to Webster's Dictionary.
One is a "weight table", the other a "mass and weight table".
If one uses units of "weight" to describe "mass", then that is incorrect, and is a bad example for students.
here are the links:
Because tons don't measure mass. They measure weight. The basic unit of mass is the kilogram. Weight is the gravitational force acting upon the object. It is a measure of FORCE, not mass, and is measured in newtons, pounds, tons, etc. Force as you recall, is mass TIMES acceleration, you take the object's mass and multiply that by the gravitational acceleration acting upon it, then you have it's weight.
Yes on earth it's fine to be clumsy and say an object "weighs" 14 tons, but whenever you're dealing with different gravity environments, you should be clear to speak in terms of mass.
I've never heard of that rule.
I've worked with lots of scientists and engineers who use "pounds mass" and "pounds weight". As long as you understand that mass is constant and weight is affected by gravity, then it all works out.
It's perfectly reasonable to me to say a ton of mass. Why should we change units?
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.