How do you determine the mass of something you can't weigh like the earth or a star?
490259
The mass of earth is found as follows.\n\nThe acceleration due to gravity at a place is g. \ng = G M/R^2, where, G is gravitational constant, which is determined experimentally with two known masses.\n\nR is the radius of earth which we know by surveying the circumference of earth.\n\n M = 9.8 x 6400,000 x 6400, 000x / 6.673x10^ (-11) = 6x10^24kg.\n\nThe mass of Sun is found as follows.  \n\nWe determine the distance of Sun observing their angular diameters measured from different heights from earth. \n\nWe observe its period of rotation about the earth.\n\nNow using the formula ‘M = 4pi^2 R^3/G T^2’, M is found\n\n39.48 x (1.496x10^11) ^ 3/6.673x10^ (-11){365.25x24x60x60}^2= 1.989x10^30 kg.\n\nSince we know the mass of Sun, we can use only the period of rotation to find the mass without knowing the distance.\n\nAbout the mass of stars, I don’t know whether there is some way to find their mass.
563922
They don't. They calculate the MASS of a planet by carefully obseving it's behavior in the gravitational field of the sun or star it orbits, and by using Keppler's Laws of Planetary motion and Newton's Laws of motion.
1042618
weight = mass x gravity\n\nso...\n\nweight / gravity = mass\n\nthe gravitational constant on earth is approx. 9 m/s^2
215801
Planets, or other celestial objects' mass may be estimated by its size and its gravitational pull on objects around them. For example, Jupiter has a high mass being the largest planet in our solar system, If a star or sun that went through supernova, and collapses into a Red/brown/white dwarf, or becomes a black hole may seem relatively small from its original size, but still retain most of their massive gravitational properties, strong enough to even bend light, is known to have a considerable amount of mass.\n\nTry this sites:\n http://www.astronomynotes.com/solarsys/s2.htm\nhttp://en.wikipedia.org/wiki/White_dwarf\n\n~meow
778402
Mass is a property of matter, it is related to its bulk; how much stuff there is. Weight is the result of a mass subjected to an acceleration, usually the gravity of a planet.  How much gravity a planet gives is a function of its mass, so smaller planet or moons will make you feel lighter (less weight) despite your constant mas.  Also, if you are in orbit, in what is called micro-gravity or free fall, you can even stop feeling any acceleration at all, hence you are weightless, but not massless. In space, you could move very large objects as they have no weight, but you could only move them slowly as your force is limited, and the mass of the object is still there.\nWeight is in direct proportion of the mass of the object attracting you, an in inverse square proportion of how far away one is from the object.\n\nThink of it as pushing a car on neutral on a flat road.  How come it takes so much strength?  Because the car has mass.  In this case, its weight is irrelevant as it it entirely supported by the wheels. But the bulk remains.  Here, the weight manifest itself by hom much compressed the tire and suspension components are squeezed.\nYou can also envision a large ship.  Again, its weight is balanced by the buoyancy of the water -- the weight determines how deep the ship sits in the water.  But try to put it in motion (you have a rope attached to it, and you are on land pulling), and that will take a lot of force.  Sure the ship will move, but that would be very slowly, because the mass of the ship is so great.
606341
It depends on whether you are talking about a planet in our solar system or an extra solar planet. I'll describe both.\n\nFor a planet in our solar system, the apparent size can be directly measured optically. One way is to take a picture of the planet through the telescope and measure the size of the picture with a ruler. Calculations based on the focal length of the telescope will tell you how many degrees (or fractions of a degree, since it will be less than 1) wide the planet appears to be in the sky for a given measured size on the photograph. Then the distance to the planet must be measured, which is not so easy. Basically it comes from triangulation to nearby asteroids combined with kepler's laws. Knowing the distance and apparent size allows you to calculate the real size and volume. To get the density, you need to know the mass. If the planet has Moons, the orbital period of the moons gives you the planet's mass from orbital mechanics calculations. If the planet has no moon, like Mercury and Venus, then theoretically their mass can be gotten from the effect their gravity has on the orbits of other planets, asteroids and comets, but this is not so accurate since those other objects don't usually pass close enough to the planet we want to measure to show much of an effect on their orbits. Fortunately we have sent space craft to Mercury and Venus and measured their mass directly by the effect their gravity had on the space craft's path.\n\nFor a planet orbiting another star, it is not so easy, because such planets cannot even be seen. Their presence is deduced from tiny Doppler shifts of the star they orbit. A planet does not just orbit a star, the star and planet orbit each other around their common center of gravity. Since the star is much heavier than the planet, it doesn't move much, but it does move, and modern instruments can measure the tiny Doppler shift in the star's light to get the motion of the star. Stellar evolution models tell us how heavy the star is and orbital mechanics tell us how heavy the planet is. (We can calculate the mass of double stars using orbital mechanics and the Doppler shift of each star's light, but we have no direct knowledge of the mass of single stars.) If the planet also happens to orbit in a plane parallel to our line of site, it will cross directly in front of the star once each orbit, like Venus sometimes crosses the face of our sun as seen from Earth. When it does, it blocks a small percentage of the star's light and the star looks slightly dimmer. If the star dims by 1%, then the disk of the planet has 1% the area of the disk of the star. Again, from stellar evolution models, we can deduce the diameter of the star and so get the diameter of the planet. (We can measure the diameter of some large, nearby stars, directly with the largest telescopes and adaptive optics, but for most stars we have no direct knowledge of their diameter.)\n\nThere is much more detail, but enough is enough, don't you think?
146781
mass = (side) x (side) x (side) or (height) x (depth) x (width)
871072
since its you science homework the answer your more than likely looking for is Newton meter, now its up to you to find out what you can on it
214139
Here is a calculator to find you weight on other planets/moons/stars,\nhttp://www.exploratorium.edu/ronh/weight/index.html
800018
the way to find the mass of an object is to divide the volume by the density it would look like this M = D / V
896953
The net force is the difference between the two weights.\n\nHowever, there is not enough information in the question to answer without making some assumptions.\n\nYou are not given the mass of the man and/or the bricks. One can calculate the mass if given the force of gravity, however you aren't given that either.\n\nOne method of solving is:\n\nASSUMING that this system is on the surface of the Earth, you can find the two masses, using F=mg with g=9.8N/kg. Once you've got that you can find the acceleration using F=ma since you know the net force and the mass of the system.\n\nMake sure you indicate which direction the acceleration is in (in this case, which object is falling, and which is being raised.
611971
Mass is a constant; weight varies by gravitational pull.
890055
Mass is measured in grams etc and is how heavy something is when no force is acting upon it.\n\nWeight is the amount of mass * gravity and should be measured in newtons.  \n\nYour mass can never change, but your weight can depending on how strong gravity is.  Eg on the moon gravity is about x5 weaker than earth, as a result you weigh x5 less than you do on earth.
406596
no idea...but I think you use the formula (Gravitational constant x mass 1 x mass 2) / distance squared
341507
You mean find "g" as if you didn't know the constant? Okay.\n\nPretty simply really. Have the height measured that you're going to drop it from to where it's going to land (this will be your "h"). Make it a high one (one meter is enough). Measure the mass of the object (that's the "w"). Then when you do the experiment, time it. Start it at the instant you let it drop and stop it once it touches where ever it lands. That's enough information to find "g." Just solve for "g" then that would be the answer.\n\nActually, for an experiment, you should solve for "g" as a formula before you start doing anything else. So the formula would be like this:\n\ng = (2h)/[(t^2)(w)]\n\n(t^2 is "t squared")\n\nSo just have that formula then do the experiment: measure height of the drop, the mass of the object, then time it when you drop it (you need good reflexes when you drop it, as it falls fast).\n\nPS Penguins!!!
3627
one estimate is about 10^52 kg, that is:\n\n\n100000000000000000000\n 00000000000000000000\n 00000000000000000000\n 000000000000 \nkilograms\n\nWithout about 90% being the "invisible" missing mass stuff.
662080
Not quite correct.  You would learn essentially the EARTH's mass by watching the moon in its orbit (actually the mass of the Earth + moon combined).  You can learn the MOONs mass most easily aqnd precisely by flying small low mass objects around each of them.  \n\nOur most precise mass estimates of solar system bodies are deduced by the impact they have on things passing near them.  Sometimes nature provides (think about the mass of Jupiter via its satellites) sometimes we do a flybay or closed orbit with a spacecraft. \n\nBy observing the motion, via doppler shifted radio signals from the spacecraft for instance, you get the velocity as a function of time.  From there it is SIMPLE to get the acceleration, and for a small mass a=GM/d^2 where M is the mass of the thing yanking on it. \n\nStars of similar mass in binary systems are trickier, though if you look at enough binary systems involving a star of one stellar type you can deduce the mass of that particular stellar type.\n\nYou can't tell the mass of a solo star directly.  You have to infer it based on the masses of other stars like it and stellar models. You can tell something about a star's  "surface" (photosphere) gravity however by the broadening of spectral lines. If you can then deduce its radius via distance and brightness measurements you can calculate the mass. This method of measuring surface gravity is a bit imprecise.  Don't expect more than one significant figure if that, which is still pretty good for astronomy.\n\nGalactic mass is easy.  Since you get the motions of individual stars  or gas clouds orbiting them, and each star has insignificant mass in comparison to the whole Kahuna, your estimates are much more precise, usually limted by how accurately you  can estimate the distance between the center of mass and the object in question.