# Gravity thought experiment

1. Jun 16, 2015

when turned off, it weighs 5kg, it is pushing down with force cca 49 Newtons

when turned on, it would weight more, lets say 6kg, pushing down with force cca 58.86 Newtons

is it in theory possible to make such device, increasing its weight continuously in the direction of gravity ?

Last edited: Jun 16, 2015
2. Jun 16, 2015

### CWatters

Not continuously. That would break Newton's laws. You could put a vertically oscillating mass inside but the average weight would be the same.

3. Jun 16, 2015

### Drakkith

Staff Emeritus
There is not. Unless you add mass to the box from outside of this system, then there is no way for its weight to increase.

4. Jun 16, 2015

### A.T.

Yes, if you pump energy into it, you can increase its mass: E=mc2

5. Jun 16, 2015

### Drakkith

Staff Emeritus
To clarify for the OP, this energy must come from outside of the box or it would already be included in the boxes mass.

6. Jun 16, 2015

### A.T.

7. Jun 16, 2015

### FL0R1

Thats not for the theory that if you put energy on it, e=mc^2 is that mass have an large energy by itself.

8. Jun 16, 2015

### FL0R1

Thats True

9. Jun 16, 2015

### Staff: Mentor

e=mc^2 works both ways: mass has energy and energy has mass.

10. Jun 16, 2015

### FL0R1

Yes it is, but in this case he powered the red box with electricity so it would electrical energy not relativity energy you saying, these are different notations :D..

11. Jun 16, 2015

### Staff: Mentor

The equation does not have any such caveats. Energy has mass. Period. If you increase the energy in the box, its mass goes up.

12. Jun 16, 2015

### FL0R1

I agree on what you are saying but here we should not mention the e= mc^2 cuz thats not for electrical energy , are you understaning what i want to sayy.
I know that if we put energy its mass goes up , i agree with that.

13. Jun 16, 2015

### Staff: Mentor

I don't think you do understand, because you are contradicting yourself and me. E=mc^2 is for all types of energy, including electrical energy. It has no caveats specifying what type of energy it works for.

Note also, the OP does not describe if any kind of energy conversion exists in the device. It may be a flywheel spinning-up or it may be a battery or it may just be getting hot. Regardless of what type of energy it stores, E=mc^2 works the same way.

14. Jun 16, 2015

### FL0R1

Imagine red box as a fully enclosed device powered by electricity.. <-- Electricity. i dont have nothing more to say..

15. Jun 16, 2015

### Staff: Mentor

What I meant was that once the electricity gets into the box, we don't know if it is converted to another type of energy.

I really can't tell here if you are not understanding or are being argumentative. I don't think what I am saying is hard to understand.

16. Jun 16, 2015

### FL0R1

No, what are you saying isnt hard to understand for me but is for others, here i tried to explain in a view of a beginners

17. Jun 16, 2015

### A.T.

Energy is energy, as Russ said. If you store more and more energy in the box, the mass of the box will increase.

18. Jun 16, 2015

### FL0R1

I know that

19. Jun 16, 2015

### Noctisdark

Adding electrical energy as you like, still you can't make such a device, you need A LOT, yes A LOT of energy to be able to make few grams, unless you power it with bunch if nuclear reactors, electric energy is motion if charged particle, these charges move inside the box, so E = mc^2 would work here, and the box can catch up some electrons but again you'll never be able to add kgs,so sorry for disappointement !

20. Jun 16, 2015

### rootone

I guess you could arrange things so that your red box has an ion drive attached to the top of it, powered by the boxes internal battery.
While drive is operational it would provide an acceleration in addition to gravity this increasing the apparent weight.
However once the ion drive is turned off the box should be lighter than it was previously since some of it's mass (the engine propellant) will have been lost,