Recent content by Gabriele Pinna

I was reading some articles about Casimir effect. It turns out that some virtual particles are created and suddenly disappears amd that these particles can exert a pressure on the plates. It seems that this creation breaks energy conservation law, but it cannot be.I would like to know which...

I would like to fine the kinetic energy of a cone that rotates around its symmetry axis. I consider that the cone is formes by infinite cylinders with different radius and infinitesimal height. I end up with this result: K=1/4w^2R^2hM where w is the angular velocity R the radius h the height and...

If there is a rotating wire in a constant magnetic field what is the direction of the induced current ? The problem is the direction of the area vector which is arbitrary, if it is parallel to the magnetic field the current will flow in a direction, if it is anti-parallel it will flow in the...

I guess C because at infinity we will have PE=0 and KE> 0 or equal to zero. As the rocket has not the tendency to move to infinity we conclude that PE+KE <0

We know that Lorentz Force is a centripetal force so: $$qVBsenx=m\frac{v^2}{r}$$ and the value of V is constant (but not the direction) But if we write: $$qvBsenx=m\frac{dV}{dt}$$ we obtain that v is exponential. What is wrong ?

We know that objects like plastic become negative (with rubbing) but what will happen if we rub plastic and plastic, one of them will become positive which one ?

Thanks

But momentum is equal to p=mv so if m=0→p=0

The mass of a photon is zero but why does it have a momentum and an energy (E=mc^2=hv) ?

I know Joule's experiment but you need to consider that the spoon has a lower temperature than coofee

Let's say that I have a spoon and a cup of coofee, I stir it with the spoon does its temperature decrease or increase ? (There is friction force so a bit of energy should turn into heat but it's strange).

What about the gravitational force acts by the Earth ?

What kind of force acts in the centre of the Earth ? What is the intensity ?

Can someone explain me what is the connetion between centrifugal force and weight force thanks ? In which situation should I use the centrifugal force (that is a fake force) ?