---
title: "A sled is given an initial horizontal velocity along a rough, horizontal snowy surface and eventually slides to a stop. A student models this situation using two different system definitions:  System 1: The sled only System 2: The sled and the snowy surface  Which of the following correctly describes the energy of the specified system as the sled slows down?"
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url: "https://nerd-notes.com/ubq/109190/"
date_modified: "2026-03-21T10:37:50+00:00"
---

# A sled is given an initial horizontal velocity along a rough, horizontal snowy surface and eventually slides to a stop. A student models this situation using two different system definitions:

System 1: The sled only
System 2: The sled and the snowy surface

Which of the following correctly describes the energy of the specified system as the sled slows down?

A sled is given an initial horizontal velocity along a rough, horizontal snowy surface and eventually slides to a stop. A student models this situation using two different system definitions:

System 1: The sled only
System 2: The sled and the snowy surface

Which of the following correctly describes the energy of the specified system as the sled slows down?

![A rectangular sled is shown on a horizontal surface. A velocity vector arrow labeled v points to the right. The surface beneath the sled is shaded with diagonal hatch marks to indicate it is rough. The boundary for System 1 is a dashed line tightly surrounding only the sled. The boundary for System 2 is a larger dashed line surrounding both the sled and a portion of the snowy surface beneath it.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1774089470-KDokdA.jpg)

- **A.** For System 1, the total mechanical energy is conserved because the normal force and gravity are perpendicular to the displacement.
- **B.** For System 1, the total mechanical energy decreases because the external force of friction does negative work on the system.
- **C.** For System 2, the total energy decreases because the non-conservative force of friction dissipates energy into the environment.
- **D.** For System 2, the total mechanical energy is conserved because the friction force is internal to the system.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/109190/*