If a two pound weight falls twice as fast as a one pound weight, how much would a weight have to be to fall at the speed of light?
A two pound weight does not fall twice as fast as a 1 pound weight (neglecting air resistance). The acceleration of gravity is independent of mass.
Rick
A two pound weight does not fall faster than a one pound weight if they are in the same gravitational field and have the same amount of wind resistance.
Examples:
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A 1 oz feather dropped from 4’ will travel slower than a 1 oz lead weight also dropped from 4’. Why? Because the feather has a higher amount of wind resistance.
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A 1 lb wood block dropped from 4’ will travel about the same speed as a 2 lb iron block also dropped from 4’, if the two blocks have roughly the same dimensions (and therefore roughly the same degree of resistance).
The reason for this is that acceleration is proportional to the mass of the attracting body (if one body, in this case the Earth, is much more massive than the other) and therefore is constant (9.80 m/s^2) regardless of the other body.
Also, no object which has mass can travel at the speed of light. Only massless particles (photons in particular) can travel at the speed of light.
“Glitch … BFG.” - Bob the Guardian
In less than 10 minutes galen has posted questions about Jesus H. Christ, speed of light, AND heavier falling faster.Granted that the SD search engine aint firing on all cylenders, but you can take your hook out of the water ,Galen.
“Pardon me while I have a strange interlude.”-Marx
Lightweight.
Peace.
Galen, where you sleeping when they covered this in 8th grade science? Maybe this will help.
Mr. K’s Link of the Month:
Guess you might as well leave it in, Galen, they’re still bitin’. if you are gonna keep this up you might wanta go here so you’ll really be prepared. http://www.bigjon.com/
“Pardon me while I have a strange interlude.”-Marx
Heheh Mr john! 
Why don’t you just leave it at: It would have to be 10 lbs.
Good answer? Sheesh!
O.K., since you guys are so smart, how fast will an object with a mass of a negative one kilogram fall at a distance of one million miles from the center of Jupiter?
This is equivalent to the amount of wood a woodchuck can chuck. Presuming, of course, that a woodchuck could chuck wood.
All questions are answered in these four threads.
http://www.straightdope.com/ubb/Forum3/HTML/003767.html
http://www.straightdope.com/ubb/Forum3/HTML/003766.html
http://www.straightdope.com/ubb/Forum3/HTML/003734.html
http://www.straightdope.com/ubb/Forum3/HTML/003613.html
I will leave it up to you to decide what the real questions are.
Dopeler effect:
The tendency of stupid ideas to seem smarter when they come at you rapidly.
Actually, the concept of a negative mass is an interesting one and I seem to remember that it was used as one of the interview question for the Westinghouse Talent Search (which I never did, but friends of mine did).
The answer is that a negative mass behaves just like a positive mass, that is it falls at the same rate. The interesting part is its effect on other masses. It repels all other masses with the same force that it is attracted to them. So if a negative mass did exist, it could be used as a propulsion system. It is always moving towards normal masses while the normal masses are moving away from it.
Just an interesting thought experiment.
TheDude
Sounds like a pretty efficient perpetual-motion machine to me.
In other words, I suspect there is an error in your research somewhere.
It’s those inefficient perpetual-motion machines that really have me puzzled.
Dopeler effect:
The tendency of stupid ideas to seem smarter when they come at you rapidly.
Well, there is no error in the thought experiment. This is simply a pretty convincing argument against the possibility of negative mass.
The funny thing is that, despite being a perpetual motion machine, it does not violate the conservation of energy, because the kinetic energy of the moving negative mass and that of the positive mass are equal and opposite, and therefore cancel to zero.
Of course, negative mass could be difficult to detect. If a pair of particles, one with negative mass and one with positive mass, were created, they would accelerate constantly until they asymptotically approached the speed of light.
TheDude
WOW! bitin so good galen’s using a doble rig!
Negative mass, i been to some of those,priest didn’t have anything good to say about anything, everybody left feelin real down.
Dude your math is off. in the equation there is only one negative,the mass. so any result will be a negative speed. Now you might claim that going backwardsis negative speed but that is relative to where you stand.( the way some of my relatives drive you wanta stand waaaaay over there) 30 kph is 30 kph no matter which way. so negative speed is a concept tha needs some thought experiments as well. sorry to be so negative,but these thinks gotta be done right. or left depending on where you stand.
“Pardon me while I have a strange interlude.”-Marx
WOW! bitin so good galen’s using a doble rig!
Negative mass, i been to some of those,priest didn’t have anything good to say about anything, everybody left feelin real down.
Dude your math is off. in the equation there is only one negative,the mass. so any result will be a negative speed. Now you might claim that going backwardsis negative speed but that is relative to where you stand.( the way some of my relatives drive you wanta stand waaaaay over there) 30 kph is 30 kph no matter which way. so negative speed is a concept tha needs some thought experiments as well. sorry to be so negative,but these thinks gotta be done right. or left depending on where you stand.
“Pardon me while I have a strange interlude.”-Marx
I sure wanna stand far aside when you get those double posts going.
But it looks to me as if negative mass is dealt with here by levity in an manner equivalent to the way gravity deals with positive mass. So, as I always suspected, levity is the exact opposite of gravity.
Ray (Would you like my “thinks” on depravity?)
It is somewhat inspired by a semi-humorous, if very geeky, faux science article written by Isaac Asimov about substances that dissolve in water in negative time. It’s simply a case of valid scientific principles being extrapolated outside their proper domain. Sometimes amusing.
TheDude