---
title: "A uniform rigid rod of length $L$ is pivotally attached to a vertical wall at its lower end. The rod is held at an angle $\\theta$ relative to the wall. A student applies a constant force of magnitude $F$ to the free end of the rod. The force vector is oriented at an angle $\\phi$ relative to the vertical wall, where $\\theta > \\phi$, as shown in the figure. Which of the following expressions correctly represents the magnitude of the torque exerted by the student’s force about the pivot?"
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url: "https://nerd-notes.com/ubq/110283/"
date_modified: "2026-04-01T04:52:16+00:00"
---

# A uniform rigid rod of length $L$ is pivotally attached to a vertical wall at its lower end. The rod is held at an angle $\theta$ relative to the wall. A student applies a constant force of magnitude $F$ to the free end of the rod. The force vector is oriented at an angle $\phi$ relative to the vertical wall, where $\theta > \phi$, as shown in the figure. Which of the following expressions correctly represents the magnitude of the torque exerted by the student’s force about the pivot?

A uniform rigid rod of length $L$ is pivotally attached to a vertical wall at its lower end. The rod is held at an angle $\theta$ relative to the wall. A student applies a constant force of magnitude $F$ to the free end of the rod. The force vector is oriented at an angle $\phi$ relative to the vertical wall, where $\theta > \phi$, as shown in the figure. Which of the following expressions correctly represents the magnitude of the torque exerted by the student's force about the pivot?

![A vertical line represents a wall. A rod of length L is attached to a pivot at the bottom of the wall and extends upward and to the right into the first quadrant. An angle theta is labeled between the vertical wall and the rod. At the top end of the rod, a force vector F is drawn. A dashed vertical line is drawn upward from the top of the rod, and an angle phi is labeled between this dashed vertical line and the force vector F. The force vector F points generally upward and to the right, but closer to the vertical than the rod is (since theta > phi).](https://nerd-notes.com/wp-content/uploads/ubq-diagrams/ubq-frq-generatedstem-fig-1-1775019136-3uMDIX.jpg)

- **A.** \(LF \sin(\theta - \phi)\)
- **B.** \(LF \sin(\theta + \phi)\)
- **C.** \(LF \cos(\theta - \phi)\)
- **D.** \(LF \sin\theta \cos\phi\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/110283/*