---
title: "Four blocks of masses \\( 20 \\, \\text{kg}, \\, 30 \\, \\text{kg}, \\, 40 \\, \\text{kg}, \\, \\text{and} \\, 50 \\, \\text{kg} \\) are stacked on top of one another in an elevator in order of decreasing mass with the lightest mass on the top of the stack. The elevator moves downward with an acceleration of \\( 3.2 \\, \\text{m/s}^2 \\). Find the contact force between the \\( 30 \\, \\text{kg} \\) and \\( 40 \\, \\text{kg} \\) masses."
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url: "https://nerd-notes.com/ubq/55428/"
date_modified: "2025-09-17T06:29:50+00:00"
---

# Four blocks of masses \( 20 \, \text{kg}, \, 30 \, \text{kg}, \, 40 \, \text{kg}, \, \text{and} \, 50 \, \text{kg} \) are stacked on top of one another in an elevator in order of decreasing mass with the lightest mass on the top of the stack. The elevator moves downward with an acceleration of \( 3.2 \, \text{m/s}^2 \). Find the contact force between the \( 30 \, \text{kg} \) and \( 40 \, \text{kg} \) masses.

Four blocks of masses \( 20 \, \text{kg}, \, 30 \, \text{kg}, \, 40 \, \text{kg}, \, \text{and} \, 50 \, \text{kg} \) are stacked on top of one another in an elevator in order of decreasing mass with the lightest mass on the top of the stack. The elevator moves downward with an acceleration of \( 3.2 \, \text{m/s}^2 \). Find the contact force between the \( 30 \, \text{kg} \) and \( 40 \, \text{kg} \) masses.

![Diagram](https://nerd-notes.com/wp-content/uploads/ubq-diagrams/nerd-notes-diagram-55428-1777289255-KUc96g.jpg)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/55428/*