my son had a simple question that is not so simple. What make one thing heavy than another.?

Question

Is it gravity or density? say if i were on the moon could i lift a car as easily as a feather?

Answer 1

Gravity.

The mass of any particular object remains constant no matter where it is. But its "Weight" (i.e. how heavy it is) depends on the gravity (where it is).

The same object can be different weights (heavy in one place, light in another)

Answer 2

First to answer your son's question, he will not be able to lift a car as easily as a feather. On the moon a feather is 1/6 the weight it is on the earth. Also on the moon a car is 1/6 the weight it is on the earth. But in both cases, the car is always many times heavier than the feather.
If a car weighs 1800 pounds on the earth, it will still weigh 300 pounds on the moon.

I hope this helps. It was a good quistion for a kid to ask.
Overall, masses in a gravity field have weight. If both masses are in the same gravity field, then the difference in weight is purely the result of mass. If you move one mass from one gravity field to another, the difference in weight is in the gravity.

Weight is a function of mass and gravity. Density really doesn't have anything to do with it. Mass is the how much material is present in an object. Density is how compacted that object is. Do you remember the old trick question of "what weighs more, a 100kg of lead or a 100kg of feathers"? The answer is neither; a 100kg is a 100kg whether it is feathers or lead. The difference is that lead is far more dense than feathers so it takes up less space.

Answer 3

Sorry, Jay T is not quite right. It's the mass of 2 objects that attract each other, not the mass of one object. If it were just the mass of the planet, then a feather would weigh as much as a lead fishing weight. This obviously isn't the case. Mass attracts mass. The more mass, in either or both objects, the more the attraction (weight). The denser an object is the more mass it has per given volume. We find it convenient to call this attraction between the mass of the earth and the mass of objects on the earth gravity.

A person can pick up a car if it weighed 1 pound but still had it's mass. He would just have to pick it up very slowly. A small push will eventually move a large mass in low or zero gravity. This is how ion engines work on spacecraft. A very small push over a very long time equals a very fast velocity. If the person has no anchor point, the the action/reaction law comes into effect. The person pushing on the car would move faster than the car would, but the car would move.

Answer 4

You're asking about two different things.

Mass is what makes one thing heavier than the other. Whichever object has more mass will be heavier (and, technically, weight is measured in pounds and mass in slugs).

The force of gravity is the attraction of two objects towards each other. It depends on the product of the two masses, as well as the universal gravitational constant and the distance between the two objects.

The Earth pulls harder on a car than you because the Earth's mass times the car's mass is a lot greater than the Earth's mass times your mass.

You and the car both have the same mass you had on Earth, however, the Moon has a lot less mass than the Earth. As a result, it takes a lot less force to overcome the Moon's gravity than it does to overcome the Earth's gravity.

But lifting a 3000 lb car won't be as easy as lifting a feather. Since the Moon has less mass and a smaller radius, the force of gravity on the Moon's surface will be about 1/6 as strong as the force of gravity on Earth. Lifting a 3000 lb car will be as easy as lifting a 500 lb donkey.

Answer 5

Gravity is the natural force of attraction between any two massive bodies, which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

Density is the mass per unit volume of a substance under specified conditions of pressure and temperature. The density of a pure substance varies little from sample to sample and is often considered a characteristic property of the substance. Most substances undergo expansion when heated and therefore have lower densities at higher temperatures.

Mass is quantitative measure of inertia, or the resistance of a body to a change in motion. The greater the mass, the smaller the change produced by an applied force. Unlike weight, the mass of an object remains constant regardless of its location. Thus, as a satellite moves away from the gravitational pull of the Earth, its weight decreases but its mass remains the same.

Simply put... the further you go away from a gravity source the easier it is to pick up a "heavy" object... however the mass of this object is still the same.

Answer 6

The gravity of a planet alone determines the weight of objects on it.

The mass remains the same regardless of gravity, since mass is the measure of material matter content, not weight.

If a heavy automobile were floating relatively motionless in weightless space, it would still be very hard to push it away from you.

If there were no gravity on earth and an automobile was weightless, it would mean that there is no force of gravity pulling it down but, contrary to popular opinion, you still could NOT lift it like a feather. You would still have to overcome its inertia (its tendency to stay put) caused by its mass and that would be a strenuous exercise. So to pick it upward would still take a considerable amount of strength to move it.

Many people who have trouble understanding science often confuse mass with weight, but they are not the same or even related. This confusion results from the fact that mass and weight can be expressed in the same units, for example pounds, even though they are completely different things.

A 50 ton mass can have a weight of 1 ounce or 1 pound or any other weight, but the mass stays constant. In similar manner, in a heavy gravity environment a pebble can weigh 500 pounds even if it has only 1/10 ounce of mass.

Things with different masses in the same gravity field will have different weights accordingly, but in zero gravity they will all be weightless regardless of their respective masses.

Density is the measure of mass per unit of volume. It does not determine the weight. Only the acting gravity determines the weight.

I hope this offers some clarification.
 

Answer 7

Mass makes one thing heavier than another. Gravity affects mass, so the more mass an object has, the more it is affected by gravity. If you took two objects and weighed them on earth and the same two objects and weighed them on mars, their masses as related to each other would be the same.

If you used a scale calibrated to earth gravity in both cases both objects weights would be .6 on Mars of what it would be on Earth.

Because your muscles are used to doing work on Earth, the lowered effect of gravity on the mass of the car would make it much heavier but it would still be pretty heavy.

Make that much liter, not heavier.

Answer 8

I woud say both but in this case the answer is density. Some objects are denser than others depending on the composition of their atoms. The gravity in the moon is about 20 times less than of earth, depending on how much the car weights you would be able to move it, but not that easily.

Answer 9

your mass would be the same on the moon as it is on earth, but your weight would be 1/6th as much, due to weaker gravity. your weight changes relative to the force of gravity, but your mass is a constant no matter where you are.

Answer 10

Most of the answers given above are correct, but they're not in the language the questioner's son would understand. Here's how I would answer the little guy.

"Planets all pull things toward themselves. That's why we don't float away. Planets pull harder on bigger things and that's why bigger things weigh more. Bigger planets pull harder than smaller planets, so a car would weigh more on a big planet than on a small planet.

Now, eat your peas.