A piece of metal and stone of same shape and size are dropeed from same hieght in earths magnetic field .Which will reach faster and why ?(Neglect air resistance)

Hi Vikash,

As the acceleration "g" is independent of the mass or shape, both will have the same velocity at any instant of time and hence will cover the same distance in the same time.

And hence both will reach the surface simultaneously.

Hope this helps.

Best Regards,

Ashwin (IIT Madras).

Stone will fall down vertically with increasing speed as it reaches the surface. At any given altitude, metal has same speed as stone. But magnetic field is always perpendicular to velocity. Therefore, metal follows curved trajectory, so stone will reach faster.

The stone will reach the surface in a lesser time as when the metal plate is dropped, eddy currects are produced in the metal plate(not in the case of stone as stone is a non conductor) and since the eddy currents opposes any change in the magnetic flux, it tends the deaccelerate the downward motion, and the metal plate has an acceleration less than g

Hi Vikash,

In case of considering the magnetic fields, this would also depend on the place where the stone and metal are droped from.

If the experiment is conducted at the Poles, then both stone and metal will reach the surface at the same time.

(As at the poles, the magnetic field would be along the direction of velocity).

On the other hand, at the equators the stone will reach earlier as the metal takes a longer route to reach the surface of the earth. (For the difference to be noticeable, the stone and metal has to be droped from a considerable height that is compareable to the radius of the earth. Else the difference would not be noticeable.

Hope it helps.

Regards,

Ashwin (IIT Madras).

Sir but in my book it is written Metal piece will take longer time due to retardation due to eddy currents .Just explain me how?

Hi Vikash,

Eddy currents are those currents that are induced in a conductor, when the conductor is exposed to a changing magnetic field.

As in the above diagram, you can see the induced Eddy Currents in the Metalic Circular Plate, when the plate is made to move down in a Magnetic field that is into the plane (The direction of this Eddy currents would be given by Lenzs Law).

Now, note that at the poles, the direction of the magnetic field will be always parallel to the direction of motion of the piece of metal. Hence no induced Eddy Currents at the Poles, as the magnetic field does not chage at the poles, with height.

But at any other place (Other than the poles, the intensity of the Magnetic Field will change with Height). So the Eddy Currents would be produced at places other than the poles which will oppose the motion of the metal.

So Stone will reach earlier, except at the poles (where both will reach at the same time). Kindly approve if this helped you.

All the best.

Regards,

Ashwin (IIT Madras).

Hi Vikash,

Here is the diagram attached.

Regards,

Ashwin (IIT Madras).

Sir all of you thankyou for your answers