Question

The Physical property "mass" is defied in 2 ways.
1. as gravitational mass.
2. as inertial mass.
According to the experiments carried out so far both of them r equivalent to each other. So Basically it can be said that there is no difference on between them except the way they r defined.
So wt troubles me is y do we consider both of these factors as 2 different concepts for the same physical property ?

Answer 1

Hi! I haven't had formal education or discussions on this topic, but I've been studying physics for a little while and I think I have a answer worth posting!

Those are two different physical phenomena, right? Gravitation between two objects, and the tendency for an object to resist changes in motion. So we should continue to see both properties.

Experiments show to a high degree of certainty that both masses are the same, right? But that doesn't mean that the causes are the same. I haven't been keeping up in particle physics, but not everything has been explained yet. To assume that there is one physical property that ties the two together might be incorrect. Even though the different measures of mass are related in our experiments, that doesn't mean that they are one in the same in terms of the physical phenomena.

Also, they are different properties of what we know as mass, and it's important to know both of them.

If, one day, we find out that there is a difference, like you can have inertia without gravitation, then the distinction will be more understandable. Until then, it's just that they are not one in the same.

In physics, I think phenomena are always defined as relations.

Answer 2

do you mean, if gravity is removed mass doesn't exist ?

if we have two obejecs, and if we are in gravity less place, guess we can identify which one is massive by putting it in each of our hand and, we can feel the massive object right ?

Answer 3

im sure im missing the important concepts... guess u folks are taking about general relativity and stuff hmm

Answer 4

I don't think we will feel the mass 'cause what we feel when an object lies on our hand is the reaction that happens against the weight of that object. So no gravity means no"g". No "g" means 0 weight which means reaction is also 0. So we won't feel anything. .... Am I right ?

Answer 5

No, I'm not bringing up special relativity! I think those two properties are still completely tied in all the theories of special relativity I've heard!

Answer 6

With the current theories I know about, if there is no gravity, we wouldn't feel the mass at rest without gravity pulling it to our hand. Still, we'll feel it when we push, as there is a resistance to motion.

Answer 7

yup ! when we push we can feel its mass, as massive object resists

Answer 8

huh.... Even if we push it it won't be the same 'cause the reaction we feel will varies with the force we apply

Answer 9

when gravity is removed, Weight becomes 0
Since mass is just a measure of number of molecules inside an object, mass we can feel, if we compare pushing two objects of different mass

Answer 10

The force from gravity is a force between masses. You need a lot of mass to make a force we can feel. So, we're usually talking about something small like a ball we can hold and something huge, like the Earth. If there was no Earth, we wouldn't notice the force on the ball. Not enough gravitational force.

Right! The force varying means we'll feel it differently.

Talking about how we feel things is difficult to explain in physical terms for me, because I don't know about the biology! I'm imagining we have sensors that send signals to our brains based on differing pressures. We do feel pressure, rather than force.

Answer 11

And the weight of those molecules, but you are right!

Answer 12

interesting, brb :)

Answer 13

Agreed :)

Answer 14

I think it's should be the point where inertia should come. the more the mass means more the inertia so I agree there should be some difference. But can we feel it ?

Answer 15

Yeah! Put two objects on ice, one heavy and one light, preferably with areas chosen to not exert different pressures on the ice. Friction will be nearly negligible. Then try to push the heavy one (like a boulder). Then try to push the light one (like a rock). Which one will resist motion more, even when the same force is applied?

Again, a human pushing is difficult to describe in physical terms...

Answer 16

And we would feel this difference in inertia. Suppose you were in outer space, far from a large mass, so gravity is so slight you wouldn't notice.

Then you push a heavy object. It still does not move as easily as a light object!

Answer 17

So, we're looking at two different properties of mass. However, nothing we try seems to show that that mass for the object is different inertially \(F=m\ a\) or gravitationally \(F=G\dfrac{m_1\ m_2}{r^2}\).

Answer 18

I guess it might be better to say \(F=G\dfrac{M\ m}{r^2}\) so we have the same \(m\).

Answer 19

yep . Agree. but I think we won't find any examples in practical life 'cause there r lot of external factors affecting on objects other than the mass of it which would act against the force we apply. for an example : - in ur example about Ice though the friction is negligible the air resistance can't be ignored and also we won't find 2 objects with the same size but with a huge mass difference in day to day life. So the physical factors would be more complicated. So I guess it's not practical to think up of 100% accurate examples

Answer 20

Any way thnks guys !

Answer 21

True! Experimenters try to isolate as much as they can, and then describe the situation as accurately as possible, find out what they expect based on current theories, and then find out what happens. If the experimental data is very different from the predictions, there is something wrong. It could just be the measuring devices. But it could also be an incorrect theory, which is where we'll be able to say that we are wrong and there is something going on that we didn't know about!

By the way, the forces from the ice exist, as does air drag. And the differences in air drag can be reduced with a good setup. Better yet, air drag will be extremely slight at low velocities, and it's effect will be hardly noticeable compared to inertia if you have more massive objects. Best yet, do it in outer space - nearly no fricition or drag!

Answer 22

You're welcome!