Why is gravitational field strength different on different planets?

Answer 1

This is due to the planets' mass, and, to some extent, its size. Before we look at the main reason, we have to consider two things, what is meant by the Centre of mass and Newton's Law of Gravity 1. Centre of mass Although the mass of any object is spread throughout that object, to an observer it seems to be concentrated in one specific point - the centre of mass (used to be called the centre of 'gravity' although that term is misleading). For an object like a guitar where there are more massive bits spread all over it and the main part is light and hollow, finding the centre of mass is difficult. However for a relatively uniform structure like a planet, the centre of mass is concentrated at the centre of the planet. 2. Newton's Law of Gravity Isaac newton found out that gravity depends upon two things: the masses of the two objects that are involved (e.g. a human and the earth - the human standing on it) and the distance between them (eg, the distance between the human, at the surface, and the centre of mass, at the centre of the earth). He found out that gravity is proportional to the masses of the wo objects multiplied together, so that as this amount increased, so would the force of gravity between them. Also he found that the nearer the objects were to each other, the more the force. In fact, if two objects were near to each other the force was strong, but it diminished rapidly by a 'square of the distance' if they were parted. This means that if two objects that were originally touching separate by, say, 2 miles, the force of gravity between them diminishes to a fourth (quarter) of its original value (2 x 2). If they separate by 3 miles, the gravity deminishes to just a ninth of its original value (3X3) and so on... separation by just 10 miles would mean gravity diminishing to just a hundredth of its value (10 x 10). So if objects are brought nearer to each other, gravity increases dramatically. Therefore, on a moderately sized planet like earth, gravity should be relatively strong as objects on the surface are nearer to the centre of mass of the planet than they would be if the planet was larger and had a larger diameter. Furthermore, on earth, the density of the planet is high (as it has a nickel/iron core) so the planet is relatively massive so again this would positively affect the size of the force of gravity on the surface. Some planets, however, are more massive (like Jupiter) and should have much higher gravitational force on the surface, but as the surface is also farther away from the centre of mass (because Jupiter is larger), this weakens the force of gravity at the surface. Therefore, instead of gravity being hundreds of times more than the earth (if the mass alone of Jupiter was taken into consideration), because the planet is so large, and the surface is further away from the centre of mass, this weakens the gravity at the surface making the gravitational pull just 2-3 times the earth's. Using the same logic, you can calculate the gravitational pulls of all the planets and moons in the solar system. Some are large, some are small, but all depend upon the size, and mass, of the planet. The force of gravity depends on the distance between objects, and on their masses. Planets have different sizes, and different densities (mass/volume). This affects the force of gravity.

Answer 2

Gravity is directly related to mass. A planet with a smaller mass than that of Earth would have less gravity, a planet more massive than Earth would have a stronger force of gravity. The moon is 1/6 the size of Earth, therefore the moon has 1/6 the force of gravity as Earth.

Answer 3

The force of gravity is described by the equation:

F =G(m1m2)/r2

where:

• F is the force between the masses,
• G is the gravitational constant,
• m1 is the first mass,
• m2 is the second mass, and
• r is the distance between the masses.

Since different planets have more or less mass than others, some have weaker gravity and others stronger. Also the force of gravity varies with the distance between an object and the planet so even though Jupiter is much more massive than the Earth, we don't normally notice any effect of the gravitational force of Jupiter because we are very close to the Earth and far, far away from Jupiter.

Answer 4

Gravity is different on different planets because the different planets have different masses. The force of gravity between two objects is proportional to their masses and inversely proportional to the square of the distance between them.

Newton's law of universal gravitation...

F = G(Mm/r2)

... where F is the force in newtons (N) of gravity between two objects, G is the universal gravitational constant, 6.674 x 10-11 N m2 kg-2, M and m are the masses of the two objects in kilograms, and r is the distance between them in meters.

Answer 5

1. The gravitational field strength is different on different planets because their attractions (that it exerts) are different, some planets have larger and stronger attractions and so their weight will be bigger than other planets whom attractions are lower. The force of the attractions depends on different factors. The first and the main obvious is the mass of the planet (because weight is calculated by multiplying the mass of the object with the gravitational field strength which differs depending on the planet), so continents contain different masses, the reason why they have different strength of attractions. Mass of the planet is not the only factor; the radius of the planet also determines its gravitational field strength, as well as the density of the planet, another reason why the force of attractions is different between the planets.

Answer 6

The gravitational attraction between two masses depends on the magnitude of both masses,
and on the distance between their centers.

When an astronaut stands on the surface of the moon or another planet, the two masses are
his mass and the mass of the body he's standing on, and the distance between their centers is
the radius of that body.

Two of these three quantities are different from what they are when he stands on Earth, so the
gravitational attraction between him and the body he's standing on is different from what it is
when he stands on Earth.

In other words, his 'weight' is different on the other body.

Answer 7

Different planets have different mass and size.

Answer 8

because gravity is relative to mass, the the more mass a planet has the greater the force of gravity, i.e. the moon has less gravity than earth cause its smaller.

Answer 9

Different planets have different weights that will either increase or decrease their gravitational pull as compared to earths

Answer 10

Gravity is the force caused by the pull of a planet's mass, some planets have a higher mass than the Earth, and so have a greater gravitational pull.