2006-12-13 21:12:09 · 9 answers · asked by Meaghan S 1 in Science & Mathematics ➔ Astronomy & Space
If the radius doubled and the mass did not, the gravity would decrease by a factor of 4.
2006-12-13 21:21:41 · answer #1 · answered by Gene 7 · 1⤊ 0⤋
Gravity is inversely proportional to square of the radius of the planet. "g = GM / (R^2). Therefore, on doubling the radius, the gravity would become 1/4th of the initial value.
2006-12-14 05:28:32 · answer #2 · answered by TG 2 · 1⤊ 0⤋
let d be the density of the material the planet is made of. let r be the initial radius. so its gravitational pull right now is GMm/r^2=G(d*4/3*pi*r^3)*m/r^2. so we see that if the planet is adding mass to itself of the same density d then the gravitational force is directly proportional to r. therefore if the radius is doubled then the pull is doubled. now if no mass is being added then the gravity reduces by 4 because 2^2 is 4.
2006-12-14 06:22:11 · answer #3 · answered by Anonymous · 0⤊ 0⤋
If the mass doesn't change, then neither does the gravity - a moon of this planet wouldn't be affected. If you're asking about the gravity at the surface of the planet then the inverse square law applies - things would only weigh a quarter of what they used to.
2006-12-14 05:50:10 · answer #4 · answered by Iridflare 7 · 0⤊ 0⤋
Sorta depends. If it just got bigger, but all that was filling it was air, it wouldn't change much, since air isn't very dense.
Gravity is all about size and density.
If something's big, but not very dense, it's graviational field will be big, but not very strong. If something's really small but super-dense, it will have a smaller gravitational field but it'll be really strong past a certian point.
Now, that's a really simplified way of saying it. Gravity works, as far as we know, across the entire universe. No matter how big, no matter how dense. You're probably pretty confused by now. Ask someone to explain to you the 'rubber sheet' gravity model, sometime.
Assuming that you meant Earth's size doubled and it's density remained the same. The gravity should double, I guess.
That other guy said a bunch of gobblitygook I didn't really read. That might be right too, I think he's BSing, though.
2006-12-14 05:21:16 · answer #5 · answered by socialdeevolution 4 · 0⤊ 1⤋
If the radius of a planet doubles, the gravity will increrase. For example, the planet jupiter or saturn are bigger then the earch and they also have a greater gravity. And the moon is smaller then the earth. which means it has a lower gravity.
2006-12-14 05:21:47 · answer #6 · answered by o cool 1 · 0⤊ 1⤋
It depends if its density stays the same or not.
Its volume would be 8 times bigger, so could its mass.
As its radius would double, its force of gravity would change according to:
F = G.M.m' / d²
where G is the gravitational constant, M its mass, m' the mass of bodies "on" or close to it, and d its new diameter (twice).
So if the mass is 8 times bigger and its diameter twice bigger:
F = G . 8M.m' / 4.d² = 8/4 = 2
The force would double, so would the gravity.
That is IF the density stays the same.
If it just "inflated" (mass stayed the same), we would have:
F = G . M . m' / 4 d² = 1/4... gravity would be 4 times less.
2006-12-14 05:22:38 · answer #7 · answered by just "JR" 7 · 1⤊ 0⤋
it'll be 4 times because acceleration due to the earth is inversely propotional to the square of radius and directly proportional to the gravitational constant and the products of the mass of the planet and object
2006-12-14 05:17:30 · answer #8 · answered by Uday K 2 · 0⤊ 2⤋
Gravity increases with the increase in mass but what that increase is, I have no idea.
2006-12-14 05:34:25 · answer #9 · answered by Ted T 5 · 0⤊ 0⤋