I am sorry rogergarrison, I should have been more specific. In my initial question I was asking about 2 different figures. The gravity the object would have and the gravity you would need to produce to allow walking on a surface.
And about the second question, if I stood in the exact same spot on a concrete surface 2 different times. One weight at say 180 lbs and the second one at 220 lbs, would gravity have to work less to hold me down? I mean the going theme in this topic is mass having gravity so wouldn't weighing less be a good thing as the planet would not have to work so hard.
I am sorry rogergarrison, I should have been more specific. In my initial question I was asking about 2 different figures. The gravity the object would have and the gravity you would need to produce to allow walking on a surface.
And about the second question, if I stood in the exact same spot on a concrete surface 2 different times. One weight at say 180 lbs and the second one at 220 lbs, would gravity have to work less to hold me down? I mean the going theme in this topic is mass having gravity so wouldn't weighing less be a good thing as the planet would not have to work so hard.
Yes, no, sorta, yes.
1: Yes, the second question is real.
2: No, I am not joking.
3: Sorta would like an answer as it is real.
4. Yes, I am not joking.
I am in a good mood.
Thanx,
Air-eek
Think about it like this... does a helium ballon lift a light object off the ground sooner than a heavy one? Yes it takes "more" gravity to hold a lighter person than a heavier one.
Or, can you jump higher on the moon? Yes.
When you say "work harder", maybe you mean would there need to be "more" gravity (a larger mass / gravitational pull?) Unless you are referring to a synthetic manufactured gravity in chich case you would need more power, which in a sense "work harder" applies.
So...are you building a death star?
Where's Marvin?
[This message has been edited by 2.5 (edited 06-20-2014).]
And about the second question, if I stood in the exact same spot on a concrete surface 2 different times. One weight at say 180 lbs and the second one at 220 lbs, would gravity have to work less to hold me down? I mean the going theme in this topic is mass having gravity so wouldn't weighing less be a good thing as the planet would not have to work so hard.
Yes, no, sorta, yes.
1: Yes, the second question is real.
2: No, I am not joking.
3: Sorta would like an answer as it is real.
4. Yes, I am not joking.
I am in a good mood.
Thanx,
Air-eek
I already answered that...
quote
Originally posted by theBDub:
Gravity is a force that will provide a (relatively) constant acceleration on earth of 9.81m/s^2. So the work being done is the negligibly the same as long as you don't start talking about the minute differences between gravity forces on different elevations...
Work is defined as Force x Displacement. Force is mass times acceleration. So if you have more mass with the same acceleration, you will need more work to go the same displacement off the ground. But if you use the same amount of work as when you had less mass, you will create less displacement.
I have to leave work and don't have time to proofread because that statement was a little confusing. Hopefully it made sense... and I was right.
The acceleration due to gravity is going to provide a constant acceleration towards the planet regardless of your mass. The acceleration is constant under a vacuum. The only different between a feather and a rock when it comes to falling towards the ground is wind pushing it around.
So let's say you're falling towards Earth as a 180 lb man, and the guy next to you is 220 lbs. The guy next to you will be falling at the same rate as you are, but more force is created with his mass and acceleration compared to yours.
The question comes in your definition of "work." Gravity doesn't work. It's an acceleration that is relatively constant on the planet. In other words, gravity doesn't need to work harder to pull anything towards it. But to combat the effects of gravity, you would need more force to lift off the ground as a heavier man because F = ma. "a" in this instance can be substitutes for "g"ravity. So F = mg. More mass means more Force is pressing against the ground as a heavier man, meaning more Force would be required to overcome that Force.
The question comes in your definition of "work." Gravity doesn't work. It's an acceleration that is relatively constant on the planet. In other words, gravity doesn't need to work harder to pull anything towards it. But to combat the effects of gravity, you would need more force to lift off the ground as a heavier man because F = ma. "a" in this instance can be substitutes for "g"ravity. So F = mg. More mass means more Force is pressing against the ground as a heavier man, meaning more Force would be required to overcome that Force.
Does that make sense?
Think about a 50 lb kid and a 300 lb man standing on earth, now imagine you could turn down earths gravity like a big volume knob. As you turned it down the kid would leave the ground first right?
Think about a 50 lb kid and a 300 lb man standing on earth, now imagine you could turn down earths gravity like a big volume knob. As you turned it down the kid would leave the ground first right?
Not unless a force acted upon them. If you turned the gravity down, and all else remained constant, they would just sit there on the ground...
Don't think so. Bdub's quote.."The acceleration due to gravity is going to provide a constant acceleration towards the planet regardless of your mass. The acceleration is constant under a vacuum. The only different between a feather and a rock when it comes to falling towards the ground is wind pushing it around."
Not unless a force acted upon them. If you turned the gravity down, and all else remained constant, they would just sit there on the ground...
If all mass has gravity other "forces" would. Ok when a force did, the lighter would first correct? That is my point.
quote
Originally posted by theBDub:
The acceleration is constant under a vacuum.
But we are not in a vacuum. Too if you are already on the ground you have no acceleration, though there is a force tugging on you. I'm not the expert here, just trying to clarify.
[This message has been edited by 2.5 (edited 06-20-2014).]
If all mass has gravity other "forces" would. Ok when a force did, the lighter would first correct? That is my point.
But we are not in a vacuum. Too if you are already on the ground you have no acceleration, thought there is a force tugging on you. I'm not the expert here, just trying to clarify.
See but now we're talking about momentum though, and not gravity at all!
So when you push something, you are not only acting upon that object. That object is also putting that same force on you! Let's say we are floating in space. Next to you is a semi truck. The other side of you floats a needle. You flick the needle and the needle goes flying. That needle actually put the exact same amount of force on you as you did on it, but because you have higher mass, your momentum is going to transfer to the needle and keep you from speeding off. Lets say you then turn and try and push the semi. Now YOU will go flying! Because the semi had higher mass.
If that's the point of the question, does that make sense?
Let's say we're at regular earth gravity. The difference between a refrigerator and a cardboard box is its mass, right? So you try and push a refrigerator, but the fridge can push back with the same force before it will move because the mass with the gravity is exerting a force on the ground (F=mg remember) and that force is acting with the stationary frictional coefficient of the ground surface. While a cardboard box has lower mass so lower force acting on the ground, easier to overcome the friction. I want to draw a diagram and show you but I'm at work.
I have no idea if this is making any sense to anyone who hasn't taken any courses. Hopefully it makes some.
And about the second question, if I stood in the exact same spot on a concrete surface 2 different times. One weight at say 180 lbs and the second one at 220 lbs, would gravity have to work less to hold me down? I mean the going theme in this topic is mass having gravity so wouldn't weighing less be a good thing as the planet would not have to work so hard.
Yes, no, sorta, yes.
Thanx,
Air-eek
sorta. The lighter person requiring less work holds true just so long as one only considers the Earth's gravitational "pull". All things with mass also have their own gravitational pull. We each, excert our own pull on the earth, just as it excerts it's 'pull' on us. Any object with a larger (heavier weight in this case) mass exerts more pull on the earth than a lighter object does. The 2 forces are cumulative.
So I suppose one could say the Earth's gravity doesn't have to "work" as hard to hold a lighter person down, but that is really kind of moot, since the Earth's gravitational pull is there regardless of whether a light (less mass) object occupies the space or a heavier (more mass) occupies the space. Even if nothing at all is there, the gravitational pull still is--there's just nothing present to feel the effect. The pull is constant, but the effect may appear not to be the same, tho the gases that surround the lighter person also contain mass so they are going to feel the effect.
Large quantities of lighter gases escape Earth's gravitational pull every year (helium and hydrogen for example) . They are simply too light for our planet's gravity to hold them as they move into the upper atmosphere. Not a problem with hydrogen, but Helium, on the other hand, is a different matter. It represents 0.00052% of the volume in our atmosphere, but it's mainly harvested from natural gas using a process called fractional distillation. Helium is becoming scarce in our planet. In fact, Cornell University physicist and Nobel Prize-winner Robert Richardson once said that each floating party balloon should have a $100 price tag, as he campaigned against the US Government decision to sell the country's helium stockpile by 2015 to keep prices down.
[This message has been edited by maryjane (edited 06-20-2014).]
See but now we're talking about momentum though, and not gravity at all!
So when you push something, you are not only acting upon that object. That object is also putting that same force on you! Let's say we are floating in space. Next to you is a semi truck. The other side of you floats a needle. You flick the needle and the needle goes flying. That needle actually put the exact same amount of force on you as you did on it, but because you have higher mass, your momentum is going to transfer to the needle and keep you from speeding off. Lets say you then turn and try and push the semi. Now YOU will go flying! Because the semi had higher mass.
If that's the point of the question, does that make sense?
Let's say we're at regular earth gravity. The difference between a refrigerator and a cardboard box is its mass, right? So you try and push a refrigerator, but the fridge can push back with the same force before it will move because the mass with the gravity is exerting a force on the ground (F=mg remember) and that force is acting with the stationary frictional coefficient of the ground surface. While a cardboard box has lower mass so lower force acting on the ground, easier to overcome the friction. I want to draw a diagram and show you but I'm at work.
I have no idea if this is making any sense to anyone who hasn't taken any courses. Hopefully it makes some.
It totally makes sense, you explain well and I understand and knew it. My problem is I think it is extraneous data.. I was like this in science class too, I was always thinking ok you are giving me lots of data, but it all seems irrelevant. I guess I am saying no matter what force may make the person want to move it will take less to move the 50 pounder. Or in another way of saying it the gravity is more effective on keeping the heavier fella in place?
[This message has been edited by 2.5 (edited 06-20-2014).]
I guess I am saying no matter what force may make the person want to move it will take less to move the 50 pounder. Or in another way of saying it the gravity is more effective on keeping the heavier fella in place?
Yes. But the gravity doesn't "work" harder, which is I guess the source of my confusion. Sorry about that.
Gravity is more effective at keeping a heavier fella in place, yes.
See but now we're talking about momentum though, and not gravity at all!
So when you push something, you are not only acting upon that object. That object is also putting that same force on you! Let's say we are floating in space. Next to you is a semi truck. The other side of you floats a needle. You flick the needle and the needle goes flying. That needle actually put the exact same amount of force on you as you did on it, but because you have higher mass, your momentum is going to transfer to the needle and keep you from speeding off. Lets say you then turn and try and push the semi. Now YOU will go flying! Because the semi had higher mass.
If that's the point of the question, does that make sense?
Let's say we're at regular earth gravity. The difference between a refrigerator and a cardboard box is its mass, right? So you try and push a refrigerator, but the fridge can push back with the same force before it will move because the mass with the gravity is exerting a force on the ground (F=mg remember) and that force is acting with the stationary frictional coefficient of the ground surface. While a cardboard box has lower mass so lower force acting on the ground, easier to overcome the friction. I want to draw a diagram and show you but I'm at work.
I have no idea if this is making any sense to anyone who hasn't taken any courses. Hopefully it makes some.
+++ to you Bdub. This subject totally facinates me. Do you and Michio Kaku have beers after work or something?
Originally posted by TheDigitalAlchemist: ...... Same way they have that "universal translator" so you don't spend the whole show/movie reading subtitles...
I always wondered about those......do they come with a "shut the frack up" option ?????
In a vacuum or 0G "weight" is relative. A planet would "weigh" the same as a person. Unless a force is inacted on it.
But......you are the pilot of a Starlifter and need to calculate your take off weight.....your limit is 323,100 lbs ----but you have 500,000 lbs of budgies in the back.
If you can fire a flare and get them all flying inside the plane at once, can you take off or will you be a fireball at the end of a runway ?
Is the downforce of thier wings in flight equal to the weight of them sitting on the deck ? Is it more ? Is it less ?
But......you are the pilot of a Starlifter and need to calculate your take off weight.....your limit is 323,100 lbs ----but you have 500,000 lbs of budgies in the back.
If you can fire a flare and get them all flying inside the plane at once, can you take off or will you be a fireball at the end of a runway ?
Is the downforce of thier wings in flight equal to the weight of them sitting on the deck ? Is it more ? Is it less ?
Yeah, I imagine the maintenance crew would have a hell of a time trying to keep the Death Star's outer hull clean. It would naturally collect space dust and debris, due to the Death Star's gravity.
The death star has some sort of a magnetic field that was strong enough to disrupt radio communications of the rebel fighters attacking it. Further, they do have some advanced force fields (as demonstrated by people standing in the landing bays as ships come and go). It's reasonable to assume that the magnetic field also helps to flow junk to specific collection points (at the poles?). I mean, we're talking about a universe where a person can just "will" a ship out of a swamp and through the air using the "force". I'm sure they have a way of keeping their ships clean that doesn't require a million squeegee kids.
To jump franchises to Babylon 5, when security was looking for missing people they thought may have been killed, they begin to check the outer surface of the station, as bodies would be pulled in due to the station's gravitational pull. (Note -- this has nothing to do with it rotating to simulate gravity via centrifugal force)
Didnt Newtons Law sort of prove that an objects weight didnt affect how gravity would act on it ...... ? If you have 1 or 2 Gs pulling on you, like say on a roller coaster, it remains 1 or 2 Gs whether you weigh 150 pnds or 250 pnds.
And about the second question, if I stood in the exact same spot on a concrete surface 2 different times. One weight at say 180 lbs and the second one at 220 lbs, would gravity have to work less to hold me down? I mean the going theme in this topic is mass having gravity so wouldn't weighing less be a good thing as the planet would not have to work so hard.
Weight is actually a measure of the force of gravity. So if one object weighs 180 lb and the other weighs 220 lb, the 220 lb object is being pulled harder by gravity. However, if both objects were dropped from the same height, they would both fall at the same rate (wind resistance notwithstanding). Because while gravity's pull changes depending on an object's mass, the acceleration caused by gravity remains the same. This distinction between the force of gravity and the acceleration due to gravity often confuses people.
I'd also like to note that a planet doesn't really "work" to pull stuff down. Gravity is an intrinsic property of the planet, created by the planet's mass. The planet doesn't have to "do anything" so to speak to make the gravity that holds you down. The gravity is just there.
Try to envision it this way: the fabric of space and time is like a trampoline, and a planet (or a star, or whatever) is like a bowling ball sitting in the middle. The mass of the bowling ball causes the trampoline to sag in the middle. So if you put a marble on the trampoline, it will naturally roll to the middle (i.e. toward the bowling ball). The bowling ball didn't have to do anything to make that happen. It just sat there on the trampoline. That's sort of how gravity works.
[This message has been edited by Blacktree (edited 06-21-2014).]
Sez the Helicopter guy--he knows everything there IS to know about gravity----but I am gonna one-upman-ship THIS time .....(no, not jumping out of a plane or free-jumpimg.......worse, a tethered edge=walk ....who wants in next weekend ? ... law of gravity, <psshhtt > yeh, I'll show ya how to break that law...(again )
Didnt Newtons Law sort of prove that an objects weight didnt affect how gravity would act on it ...... ? If you have 1 or 2 Gs pulling on you, like say on a roller coaster, it remains 1 or 2 Gs whether you weigh 150 pnds or 250 pnds.
Well the law was just a theory in newtons time. They proved ( in one example ) it on the moon when they dropped the hammer ( or wrench.. whatever ) and a feather.
I'd imagine in the Death Star something moresinister similar is working in there perhaps plasma or some liquid metal through all those large tubes that Luke Skywalker fell down into (or towards) in the closing scenes of the Empire Strikes Back.
[This message has been edited by htexans1 (edited 06-21-2014).]
And about the second question, if I stood in the exact same spot on a concrete surface 2 different times. One weight at say 180 lbs and the second one at 220 lbs, would gravity have to work less to hold me down? I mean the going theme in this topic is mass having gravity so wouldn't weighing less be a good thing as the planet would not have to work so hard.
Gravity is measured as an acceleration. Drop two objects of different mass from the same height and neglecting wind resistance, they'll fall at exactly the same rate. Naturally, the impact of a pebble will be less than the impact of a boulder. That's where the proportional force comes into play. Acceleration due to gravity is a constant, but the force due to gravity is proportional to mass.
[This message has been edited by Formula88 (edited 06-21-2014).]
Didnt Newtons Law sort of prove that an objects weight didnt affect how gravity would act on it ...... ? If you have 1 or 2 Gs pulling on you, like say on a roller coaster, it remains 1 or 2 Gs whether you weigh 150 pnds or 250 pnds.
Yes. If these two men are on a roller coaster, and they are on a 2G turn, then the 150lb man would feel like he was 300lbs, while the 250lb man would feel 500lbs. The G-force would be the same, the apparent weight would be different, based on their weight under 1G. Similarly, if these men were on the moon, the 150lb man would weigh 25lbs, while the 250lb man would be 43lbs.
I"m not sorry for hijacking this thread - GUYS! I need your help naming a force.It's not gravity, but there's some *force* out there... , Whenever I go outside without a shirt, women stick to me as if I'm magnetic. What do you call THAT? (woa, do you talk to you mother with that mouth?!?)
that's "animal magnetism". it also explains why dogs gravitate to your leg.
Didnt Newtons Law sort of prove that an objects weight didnt affect how gravity would act on it ...... ? If you have 1 or 2 Gs pulling on you, like say on a roller coaster, it remains 1 or 2 Gs whether you weigh 150 pnds or 250 pnds.
Again though arent we talking about vacuums vs earths atmosphere. If that were true on earth it would be as easy to carry a 400 lb person as it would a 50 lb person. But maybe it is true in the sense that gravity doesnt act on it differently, but it is in a sense more effective. Like I meant when I said the lighter person would float away first.
[This message has been edited by 2.5 (edited 06-23-2014).]
Again though arent we talking about vacuums vs earths atmosphere. If that were true on earth it would be as easy to carry a 400 lb person as it would a 50 lb person. But maybe it is true in the sense that gravity doesnt act on it differently, but it is in a sense more effective. Like I meant when I said the lighter person would float away first.
Roger's right. Gravity acts the same. The force due to gravity is proportional to mass, which is why 400lb feels heavier than 50lb. The acceleration due to gravity is constant. Force = mass * acceleration Acceleration in this case is due to gravity. On earth, that's 1g.
F = mass * g
It should be obvious if the mass is higher, the Force will be higher - but gravity has not changed.
Also, don't confuse mass with weight. An object in space may be "weightless" but it's mass hasn't changed. The Force is lower because the acceleration due to gravity is close to zero. And no, the lighter person wouldn't float away first. As you reduce "g" closer to zero, the force acting on both people, though different, is still greater than zero - so they don't float away. The force reaches zero when g reaches zero - so it would happen at the same time. Even then, they wouldn't float away. Some force would have to give them a slight nudge to get them moving.
[This message has been edited by Formula88 (edited 06-23-2014).]
Roger's right. Gravity acts the same. The force due to gravity is proportional to mass, which is why 400lb feels heavier than 50lb. The acceleration due to gravity is constant. Force = mass * acceleration Acceleration in this case is due to gravity. On earth, that's 1g.
F = mass * g
It should be obvious if the mass is higher, the Force will be higher - but gravity has not changed.
Also, don't confuse mass with weight. An object in space may be "weightless" but it's mass hasn't changed. The Force is lower because the acceleration due to gravity is close to zero. And no, the lighter person wouldn't float away first. As you reduce "g" closer to zero, the force acting on both people, though different, is still greater than zero - so they don't float away. The force reaches zero when g reaches zero - so it would happen at the same time. Even then, they wouldn't float away. Some force would have to give them a slight nudge to get them moving.
Yes it seems we are all talking about the same thing just looking at it differently. Kind of story of my life. Kinda sad the OP doesnt give opinion.
I'm getting a headache! 
I GOTTA learn to read the entire username...<sigh> Its only been 7 almost 8 years and I STILL aint figgured that one out !! 
