---
title: "A block of mass  \\(M\\)  floats in a container of liquid. When the block is in equilibrium,  \\(20\\%\\)  of its volume is submerged below the surface of the liquid. A student then pushes the block down and holds it at rest so that  \\(80\\%\\)  of its volume is submerged. What is the magnitude of the downward force that the student must exert on the block?"
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url: "https://nerd-notes.com/ubq/109798/"
date_modified: "2026-03-26T05:50:26+00:00"
---

# A block of mass 
\(M\)
 floats in a container of liquid. When the block is in equilibrium, 
\(20\%\)
 of its volume is submerged below the surface of the liquid. A student then pushes the block down and holds it at rest so that 
\(80\%\)
 of its volume is submerged. What is the magnitude of the downward force that the student must exert on the block?

A block of mass 
\(M\)
 floats in a container of liquid. When the block is in equilibrium, 
\(20\%\)
 of its volume is submerged below the surface of the liquid. A student then pushes the block down and holds it at rest so that 
\(80\%\)
 of its volume is submerged. What is the magnitude of the downward force that the student must exert on the block?

![Two side-by-side diagrams of a rectangular block in a liquid. On the left, labeled 'Initial State', the block floats freely with a small portion (approximately one-fifth) of its height below the water line. On the right, labeled 'Final State', a hand is shown pushing down on the top of the same block so that a much larger portion (approximately four-fifths) of its height is below the water line.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1774504226-NaxKOL.jpg)

- **A.** \(0.6 Mg\)
- **B.** \(3 Mg\)
- **C.** \(4 Mg\)
- **D.** \(5 Mg\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/109798/*