What defines our weight on earth (as opposed to other planets.)Is it size or weight of the planet in question?

Question

So if the earth and the moon had their current size, but equal weight (or density not sure how to define), would we weigh the same. As it stands now, you can bounce around on the moon. I am curious as it relates to dinosaurs roaming the earth. Something must have happened (cosmically) to the earth that allowed things to get that large. I dont think they just evolved that way. I often wonder if the earths weight has changed over time (weight of meteors over millions of years) effecting the gravity on the earths surface, phasing out larger creatures. But I dont even know if it's the earths actual size or weight (or maybe even spin) that holds us to the surface. Thanks!!!

so check this out: http://www.youtube.com/watch?v=oJfBSc6e7QQ

Answer 1

An object's weight is calculated by multiplying its mass (the amount of matter it has) by the acceleration due to gravity of the planet (or moon) that object is on.

What is meant by the acceleration due to gravity?
It is the rate of acceleration of an object if it was to fall freely from a height somewhere above the surface of the planet.

The acceleration due to gravity on Earth is 9.81 meters per second per second.

So if you were to drop a ball from the top of the Empire State Building, the speed at which it falls to the Earth will increase by 9.81 meters per second every second. After 5 seconds of falling, its' speed would be about 50 meters per second.

The acceleration due to gravity depends on the gravitational field strength of the planet where the object is. The gravitational field strength depends on the planet's mass.
So a more massive planet will have a stronger gravitational field and a greater acceleration due to gravity and vise versa.

The weight of the planet will not affect your own weight. There really isn't such thing as "weight" of a planet. Instead, mass is the more accurate term.

Answer 2

our weight depends on the gravity of the planet or moon we are on.

gravity is defined by mass, the more mass the more gravity. people usually mix up mass and weight, but they are 2 very different things. mass always stays the same, weight changes. kilograms (for example) is a unit of mass. if ur mass is 100kg on earth it will be 100 kg everywhere. weight (lbs) changes. the earth (or any other large object in space) have no weight, only mass.

the moon has 1/6 the mass of earth, so if you were on the moon you would weigh 1/6 what you would on earth.

the fact that dinosaurs were large has nothing to do with the earths gravity. most likely there was a need for them to be large, they needed to be big to survive. so evolution slowly took over and they grew.

like i said before, what holds everything to earths surface is gravity. all matter attracts eachother. we dont know exactly the mechanism that drives this, we just know its true. its what keeps the earth moving around the sun and the moon moving around earth.

this is one way to look at it. picture space as a trampoline. not the space u see with all the stars, but the area that those stars fit into. physics says thats an actual object. and mass warps space, like a bowling ball on a trampoline. if you put a bowling ball on a trampoline the trampoline would sag and anything else on the trampoline would roll towards it. if you were to put a golf ball on there and give it a push it would "orbit" the bowling ball for a second. it eventually hits it because friction slows it down.

theres a few problems with this view though. 1) everything falls towards the bottom, not the center. 2) it portrays space as a 2 dimensional object with 3 dimensional mass on it. im not going to go into this in depth here, but if you have an advanced knowledge of it you will figure it out. its mostly that everything would have to be on one plane, which it isnt. so space has to be 3 dimensional.

hope i didnt bore you or confuse u.

Answer 3

What we experience as "weight" is simply due to the gravitational force of the Earth pulling on us.
The strength of that force is directly related to the mass of the Earth (or whatever other planet we are on) and indirectly related to the square of the radius of the planet.

The moon has 1/81 the mass of the Earth, but its also smaller, so it works out that the gravity on the moon's surface is one sixth what it is on Earth.

Dinosaurs came in all sizes, from the size of a mouse to the huge ones we think of (like brontosaurs etc.).
In nature, the larger the animal the fewer predators it has and the more it is able to dominate the environment.
So the large dinosaurs did evolve that way - they had 160 million years to evolve all types and sizes.

The mass of the Earth when it finally cooled enough to allow liquid water (and life) to form about 3.8 billion years ago is estimated to have almost the same mass as today. Meteors over billions of years have added mass to the Earth, but it has also lost some mass in that time through the loss of lighter gases to space.

Answer 4

It is the mass and radius of the planet. Use the equation m/r^2.

so if the mass is the same but the radius is half then the gravity would be 4 X stronger on the surface of the smaller planet.

So in the case of our Moon the radius is about 1/4 of Earth but the mass is about 1/100 of the Earth, which gives a gravity of about 1/6 of Earth.

Answer 5

"...if the earth and the moon had their current size, but equal weight (or density not sure how to define), would we weigh the same..."
The correct word you want in this sentence is 'mass.' If Earth and the moon had the same mass but their current diameters you'd weigh *more* on the moon because you'd be closer to its center of mass (1,738 km) than on Earth (6,128 km).

Gravity is what holds us to Earth's surface. There is probably some limit to the size an animal species could attain in our gravitational field, but obviously the dinosaurs didn't reach it because there were some huge dinosaurs.

Earth's mass increases roughly by some 40,000 metric tons per year from meteorites and infalling cometary dust, but given its size and total mass that's hardly a drop in the bucket as far as affecting its gravity.

Answer 6

It's not strictly the size of the Earth. It's the earth's gravitational pull (towards the Earth's core). The larger a planet is generally the less gravitational pull there is because the further from the center of the planet you are. The mass (how much matter an object takes up) of the object also determines the weight of the object.

Answer 7

Yes it is all about gravity, some celestial bodys have more gravity than others, examples would be earth compared to jupiter, where jupiter has way more gravity and then compare this to say a moon at Mars or even the planet mars, There are variable differences in gravity everywhere in space and on celestial bodys, Dinos, were big due to evolution, then as time went on they became smaller to better suit there surroundings and food chains,;

Happy Holidays;

SG

Answer 8

It is not the planets weight, it is the planets mass. Weight is determined by the amount mass the two objects have. In our case, its the mass of our body and the mass of the Earth and the gravitational pull generated by those two masses. Obviously our mass is insignificant when compare to the Earths's but still counts in the equation. When you are on the Moon which has one-sixth the mass of Earth and your mass being the same as it is on Earth, you only experience one-sixth of the weight you do on Earth.

Answer 9

It is the mass of the body (planet or moon) in question. For example, a person's weight is about six times more on the earth than on the earth's moon.

Answer 10

What defines our weight on Earth is the gravitational force that keeps us sticked to the surface. This force is a consequence of the mass of the Earth, our mass and the distance between both masses.