---
title: "A collimated beam of ions, each with positive charge \\( +q \\) and mass \\( m \\), enters the region between two horizontal parallel conducting plates with a range of initial speeds. Inside this region, a uniform electric field \\( \\vec{E} \\) is directed vertically downward and a uniform magnetic field \\( \\vec{B} \\) is directed perpendicularly into the page. Three specific groups of ions within the beam have speeds \\( v_1  \\dfrac{E}{B} \\). Which of the following diagrams best represents the trajectories of these three groups of ions as they pass between the plates?"
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url: "https://nerd-notes.com/ubq/124944/"
date_modified: "2026-09-28T14:12:04+00:00"
---

# A collimated beam of ions, each with positive charge \( +q \) and mass \( m \), enters the region between two horizontal parallel conducting plates with a range of initial speeds. Inside this region, a uniform electric field \( \vec{E} \) is directed vertically downward and a uniform magnetic field \( \vec{B} \) is directed perpendicularly into the page. Three specific groups of ions within the beam have speeds \( v_1  \dfrac{E}{B} \). Which of the following diagrams best represents the trajectories of these three groups of ions as they pass between the plates?

A collimated beam of ions, each with positive charge \( +q \) and mass \( m \), enters the region between two horizontal parallel conducting plates with a range of initial speeds. Inside this region, a uniform electric field \( \vec{E} \) is directed vertically downward and a uniform magnetic field \( \vec{B} \) is directed perpendicularly into the page. Three specific groups of ions within the beam have speeds \( v_1 < \dfrac{E}{B} \), \( v_2 = \dfrac{E}{B} \), and \( v_3 > \dfrac{E}{B} \). Which of the following diagrams best represents the trajectories of these three groups of ions as they pass between the plates?

![A schematic diagram showing two horizontal parallel line segments of equal length, one positioned directly above the other. Above the top line segment is a row of three plus signs. Below the bottom line segment is a row of three minus signs. In the region between the line segments, three downward vertical arrows are spaced horizontally, each labeled \vec{E}. In the same region, four cross symbols are arranged in a two-by-two grid, with a single label \vec{B} to the right. To the left of the line segments, a horizontal arrow points to the right toward the central opening between the plates. At the tail of this arrow is a small filled circle labeled +q, and above the arrow shaft is the label \vec{v}. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-diagram-1-1790604721-ph98D2.jpg)

- **A.** Diagram A
- **B.** Diagram B
- **C.** Diagram C
- **D.** Diagram D

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/124944/*