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PHY 101 PHY 101 Past Questions Objective Question
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Question

An electric fan is turned off and its angular velocity decreases uniformly from 500 rev/min to 200 rev/min in 4.00 s. Find the angular acceleration in rev/s² and the number of revolutions made by the motor.
Options
A 1.25 rev/s², 23.3 rev
Correct Answer
B 1.32 rev/s², 23.3 rev
C 2.52 rev/s², 7.3 rev
D 5.25 rev/s², 23.5 rev
Correct Answer

Option A is the correct answer.

Detailed Explanation

Convert to rev/s: ω₀ = 500/60 = 8.333 rev/s, ω = 200/60 = 3.333 rev/s. α = (ω - ω₀)/t = (3.333 - 8.333)/4 = (-5)/4 = -1.25 rev/s² (magnitude 1.25). Number of revolutions = average angular velocity × time = ((8.333 + 3.333)/2) × 4 = (11.666/2) × 4 = 5.833 × 4 = 23.33 rev.

Hint

Use α = (ω - ω₀)/t and θ = (ω₀ + ω)t/2.

Question Info

Course: PHY 101
Topic: PHY 101 Past Questions
Type: Objective
Difficulty: Not specified
Question 872 of 1250
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