Q118 / 150 · MHT CET 2026 (13 April Shift 2) · Physics
Spherical insulating ball and a spherical metallic ball of same size and mass are dropped from the same height. Choose the correct statement out of the following {Assume negligible air friction}
- ATime taken by them to reach the earth's surface will be independent of the properties of their materials.
- Correct answerBInsulating ball will reach the earth's surface earlier than the metal ball.
- CBoth will reach the earth's surface simultaneously.
- DMetal ball will reach the earth's surface earlier than the insulating ball.
Solution
As the metallic ball falls through the Earth's magnetic field, it cuts the magnetic field lines, which induces an electromotive force (EMF) in it.
Since the ball is a conductor, this induced EMF generates eddy currents within the metallic ball.
According to Lenz's law, these eddy currents oppose the motion that causes them, creating an upward magnetic retarding force.
As a result, the net downward acceleration of the metallic ball becomes less than the acceleration due to gravity $g$.
The insulating ball is a non-conductor, so no eddy currents are induced in it. It falls with the full acceleration $g$.
Because the insulating ball has a greater downward acceleration, it will reach the Earth's surface earlier than the metallic ball.
Answer: Insulating ball will reach the earth's surface earlier than the metal ball.
Since the ball is a conductor, this induced EMF generates eddy currents within the metallic ball.
According to Lenz's law, these eddy currents oppose the motion that causes them, creating an upward magnetic retarding force.
As a result, the net downward acceleration of the metallic ball becomes less than the acceleration due to gravity $g$.
The insulating ball is a non-conductor, so no eddy currents are induced in it. It falls with the full acceleration $g$.
Because the insulating ball has a greater downward acceleration, it will reach the Earth's surface earlier than the metallic ball.
Answer: Insulating ball will reach the earth's surface earlier than the metal ball.
Hence, the correct answer is option: 'B'.