---
title: "Two pendulums of identical dimensions and mass are suspended from rigid lightweight rods and released from rest from the same initial angle. Pendulum 1 has a solid copper plate at its swinging end, while Pendulum 2 has a copper plate with narrow vertical slots cut into it to form a comb-like structure. Both pendulums swing downward into a region containing a uniform magnetic field directed perpendicular to their plane of oscillation. Which pendulum experiences greater magnetic damping as it enters the magnetic field, and why?"
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url: "https://nerd-notes.com/ubq/123188/"
date_modified: "2026-09-28T11:57:52+00:00"
---

# Two pendulums of identical dimensions and mass are suspended from rigid lightweight rods and released from rest from the same initial angle. Pendulum 1 has a solid copper plate at its swinging end, while Pendulum 2 has a copper plate with narrow vertical slots cut into it to form a comb-like structure. Both pendulums swing downward into a region containing a uniform magnetic field directed perpendicular to their plane of oscillation. Which pendulum experiences greater magnetic damping as it enters the magnetic field, and why?

Two pendulums of identical dimensions and mass are suspended from rigid lightweight rods and released from rest from the same initial angle. Pendulum 1 has a solid copper plate at its swinging end, while Pendulum 2 has a copper plate with narrow vertical slots cut into it to form a comb-like structure. Both pendulums swing downward into a region containing a uniform magnetic field directed perpendicular to their plane of oscillation. Which pendulum experiences greater magnetic damping as it enters the magnetic field, and why?

![Two pendulum setups side by side labeled Pendulum 1 and Pendulum 2. A horizontal support line at the top anchors two vertical pivot lines. From the left pivot, a thin vertical rod connects to a solid filled gray rectangle labeled Plate 1. From the right pivot, a thin vertical rod connects to an identical rectangular outline labeled Plate 2, containing four vertical rectangular cutouts extending from the bottom upward, dividing the plate into comb-like teeth. Below both resting pendulums is a dashed rectangular region containing six evenly spaced cross marks indicating a uniform magnetic field directed into the page, labeled \vec{B}. Curved dashed arrows indicate the downward swing direction of both plates toward the magnetic field region. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1790596672-hEdABp.jpg)

- **A.** Pendulum 1 experiences greater magnetic damping because large-area eddy current loops can freely circulate through the continuous plate with low electrical resistance, producing a larger opposing magnetic force.
- **B.** Pendulum 1 experiences greater magnetic damping because copper is a strongly ferromagnetic material that experiences a permanent magnetic attraction toward the external field region.
- **C.** Pendulum 2 experiences greater magnetic damping because cutting vertical slots increases the total exposed perimeter, which increases the rate of change of magnetic flux through the plate.
- **D.** Both pendulums experience the same magnetic damping because the total magnetic flux entering both plates per unit time depends only on the overall plate width and velocity.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123188/*