---
title: "A high-speed flywheel in a motor is spinning at \\( 500 \\) \\( \\text{rpm} \\) when a power failure suddenly occurs. The flywheel has a mass of \\( 40 \\) \\( \\text{kg} \\) and a diameter of \\( 75 \\) \\( \\text{cm} \\). The power is off for \\( 30 \\) \\( \\text{s} \\) and during this time the flywheel slows due to friction in its axle bearings. During this time the flywheel makes \\( 200 \\) complete revolutions."
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url: "https://nerd-notes.com/ubq/80837/"
date_modified: "2025-03-11T05:34:58+00:00"
---

# A high-speed flywheel in a motor is spinning at \( 500 \) \( \text{rpm} \) when a power failure suddenly occurs. The flywheel has a mass of \( 40 \) \( \text{kg} \) and a diameter of \( 75 \) \( \text{cm} \). The power is off for \( 30 \) \( \text{s} \) and during this time the flywheel slows due to friction in its axle bearings. During this time the flywheel makes \( 200 \) complete revolutions.

A high-speed flywheel in a motor is spinning at \( 500 \) \( \text{rpm} \) when a power failure suddenly occurs. The flywheel has a mass of \( 40 \) \( \text{kg} \) and a diameter of \( 75 \) \( \text{cm} \). The power is off for \( 30 \) \( \text{s} \) and during this time the flywheel slows due to friction in its axle bearings. During this time the flywheel makes \( 200 \) complete revolutions.

**Part a)** At what rate is the flywheel spinning when the power comes back on? *(3 points)*

**Part b)** If the power had not come back, how long it would have taken for the flywheel to stop and how many revolutions would it have made during this time? *(3 points)*


*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/80837/*