Two Spherical Bobs, One Metallic and the Other of Glass, of the Same Size Are Allowed to Fall Freely from the Same Height Above the Ground. Which of the Two Would Reach Earlier and Why? - Physics

Two spherical bobs, one metallic and the other of glass, of the same size are allowed to fall freely from the same height above the ground. Which of the two would reach earlier and why?

Solution

A glass bob is non-conducting, while a metallic bob is conducting. Due to the non-conducting nature of the glass bob, it will only experience the Earth's gravitational pull. So, the glass bob will reach the ground earlier.

Because of its conducting nature, Eddy current is induced in the metallic bob as it falls through the magnetic field of the Earth.

By Lenz's law, the current induced is such that it opposes the motion of the metallic bob. So, the metallic bob will experience a force in the upward direction. This will slow down the metallic bob by some extent. Hence, it will reach the Earth after the glass bob

Concept: Eddy Currents
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2013-2014 (March) Delhi Set 1

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