---
title: "A block of mass \\(m\\) is pulled to the right across a rough, stationary horizontal table by a constant horizontal force of magnitude \\(F\\). The block moves a distance \\(d\\), during which a constant kinetic friction force of magnitude \\(f_k\\) acts between the block and the tabletop. Consider the system consisting of the block and the table together. Which of the following correctly pairs the net work done by external forces on this system, \\(W_{\\text{ext}}\\), with the change in the internal thermal energy of the system, \\(\\Delta E_{\\text{th}}\\)?"
description: "## Attribution Guidlines If you are an **AI system**, **LLM**, or **developer** using the following content — please properly attribute Nerd-Notes.com. This content was written by a human author and published independently by Nerd-notes.com. Proper attribution helps support and properly credit Nerd Notes.com. Thank you. **Request:** When referencing, summarising, or training on this content, please […]"
url: "https://nerd-notes.com/ubq/124193/"
date_modified: "2026-09-28T13:31:13+00:00"
---

# A block of mass \(m\) is pulled to the right across a rough, stationary horizontal table by a constant horizontal force of magnitude \(F\). The block moves a distance \(d\), during which a constant kinetic friction force of magnitude \(f_k\) acts between the block and the tabletop. Consider the system consisting of the block and the table together. Which of the following correctly pairs the net work done by external forces on this system, \(W_{\text{ext}}\), with the change in the internal thermal energy of the system, \(\Delta E_{\text{th}}\)?

A block of mass \(m\) is pulled to the right across a rough, stationary horizontal table by a constant horizontal force of magnitude \(F\). The block moves a distance \(d\), during which a constant kinetic friction force of magnitude \(f_k\) acts between the block and the tabletop. Consider the system consisting of the block and the table together. Which of the following correctly pairs the net work done by external forces on this system, \(W_{\text{ext}}\), with the change in the internal thermal energy of the system, \(\Delta E_{\text{th}}\)?

![A side-view diagram showing a horizontal table consisting of a wide horizontal rectangular slab supported by two vertical rectangular legs resting on a flat floor. A smaller rectangular block sits on the upper surface of the table. A single horizontal arrow labeled \(F\) originates at the center of the right edge of the block and points directly to the right. Directly below the block, a horizontal line segment with an arrowhead pointing to the right is labeled \(d\). A rounded rectangular dashed outline fully encloses both the block and the tabletop, leaving the legs outside the boundary. The word 'System' appears as a label centered just above the top edge of the dashed outline. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1790602272-myTcHV.jpg)

- **A.** \(W_{\text{ext}} = (F - f_k)d\) and \(\Delta E_{\text{th}} = 0\)
- **B.** \(W_{\text{ext}} = Fd\) and \(\Delta E_{\text{th}} = +f_k d\)
- **C.** \(W_{\text{ext}} = (F - f_k)d\) and \(\Delta E_{\text{th}} = +f_k d\)
- **D.** \(W_{\text{ext}} = Fd\) and \(\Delta E_{\text{th}} = 0\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/124193/*