---
title: "A uniform thin rod of mass \\(M\\) and length \\(L\\) is pivoted at one end about a fixed, frictionless horizontal axle at point \\(O\\). The rod is held horizontally and released from rest, allowing it to swing downward in a vertical plane. Which of the following diagrams best represents the direction and relative magnitude of the force \\(\\vec{F}_P\\) exerted by the pivot on the rod at the instant of release and at the instant the rod passes through the vertical position?"
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url: "https://nerd-notes.com/ubq/124447/"
date_modified: "2026-09-28T14:05:34+00:00"
---

# A uniform thin rod of mass \(M\) and length \(L\) is pivoted at one end about a fixed, frictionless horizontal axle at point \(O\). The rod is held horizontally and released from rest, allowing it to swing downward in a vertical plane. Which of the following diagrams best represents the direction and relative magnitude of the force \(\vec{F}_P\) exerted by the pivot on the rod at the instant of release and at the instant the rod passes through the vertical position?

A uniform thin rod of mass \(M\) and length \(L\) is pivoted at one end about a fixed, frictionless horizontal axle at point \(O\). The rod is held horizontally and released from rest, allowing it to swing downward in a vertical plane. Which of the following diagrams best represents the direction and relative magnitude of the force \(\vec{F}_P\) exerted by the pivot on the rod at the instant of release and at the instant the rod passes through the vertical position?

![A schematic diagram showing a horizontal uniform thin rod of length \(L\) and mass \(M\). The left end of the rod is attached to a fixed pivot represented by a small shaded circular hinge labeled \(O\). A downward vertical arrow to the left of the pivot is labeled \(g\). The rod extends horizontally to the right from the pivot. A dashed circular arc curves downward and to the left from the right tip of the horizontal rod to a second, dashed outline of the rod hanging vertically downward from pivot \(O\). An open curved arrow along the dashed arc indicates the clockwise direction of swing. A horizontal dimension line spanning the top of the horizontal rod is labeled \(L\). A small black dot at the geometric center of the horizontal rod marks the center of mass. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1790604332-drhEAv.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/124447/*