---
title: "Two boxes are tied together by a string and are sitting at rest on a frictionless surface. Between the two boxes is a massless compressed spring. The string trying the two boxes is then cut and the spring expands, pushing the boxes apart. The box on the left  has four times the mass of the box on the right. "
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url: "https://nerd-notes.com/ubq/22725/"
date_modified: "2025-10-16T20:13:24+00:00"
---

# Two boxes are tied together by a string and are sitting at rest on a frictionless surface. Between the two boxes is a massless compressed spring. The string trying the two boxes is then cut and the spring expands, pushing the boxes apart. The box on the left  has four times the mass of the box on the right. 

Two boxes are tied together by a string and are sitting at rest on a frictionless surface. Between the two boxes is a massless compressed spring. The string trying the two boxes is then cut and the spring expands, pushing the boxes apart. The box on the left  has four times the mass of the box on the right.

**Part a)** After the string is cut and the boxes lose contact with the spring, will the magnitude of the momentum of the box on the left be (i) greater than, (ii) less than, or (iii) equal to the magnitude of the momentum of the box on the right? Explain your reasoning. *(3 points)*

**Part b)** At the instant (after the string is cut) that the boxes lose contact with the spring, will the speed of the box on the left be (i) greater than, (ii) less than, or (iii) equal to the speed of the box on the right? Explain your reasoning. *(3 points)*


*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/22725/*