---
title: "A block of mass \\(m\\) is pushed up a rough incline at a constant speed by an external force of magnitude \\(F_{ext}\\) acting parallel to the incline. The block is moved from the bottom of the incline to a final height \\(h\\). Which of the following correctly compares the work done by the external force, \\(W_{ext}\\), to the change in the gravitational potential energy of the block-Earth system, \\(\\Delta U_g\\), and provides a correct justification?"
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url: "https://nerd-notes.com/ubq/110364/"
date_modified: "2026-04-02T05:13:54+00:00"
---

# A block of mass \(m\) is pushed up a rough incline at a constant speed by an external force of magnitude \(F_{ext}\) acting parallel to the incline. The block is moved from the bottom of the incline to a final height \(h\). Which of the following correctly compares the work done by the external force, \(W_{ext}\), to the change in the gravitational potential energy of the block-Earth system, \(\Delta U_g\), and provides a correct justification?

A block of mass \(m\) is pushed up a rough incline at a constant speed by an external force of magnitude \(F_{ext}\) acting parallel to the incline. The block is moved from the bottom of the incline to a final height \(h\). Which of the following correctly compares the work done by the external force, \(W_{ext}\), to the change in the gravitational potential energy of the block-Earth system, \(\Delta U_g\), and provides a correct justification?

![A block on an incline angled at theta. A vector arrow labeled F_ext points up the incline. A dashed vertical line indicates the total height change h from the bottom to the top.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1775106833-aEESOt.jpg)

- **A.** \(W_{ext} > \Delta U_g\) because the external force must do work to both increase the gravitational potential energy of the system and compensate for the energy dissipated by friction.
- **B.** \(W_{ext} = \Delta U_g\) because the block is moving at a constant speed, meaning the total work done on the block is zero and the external work only accounts for the change in potential energy.
- **C.** \(W_{ext} < \Delta U_g\) because the force of gravity does work on the block as it moves up the incline, reducing the total amount of work required from the external source.
- **D.** \(W_{ext} > \Delta U_g\) because the net work done on the block must be positive for the block to maintain its upward motion against the force of gravity.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/110364/*