Rotational Kinematics
A flywheel starts from rest and attains an angular velocity of 60 rad/s in 12 seconds under a constant angular acceleration. What is the angular acceleration of the flywheel during this interval?
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About This Question
- Subject
- physics
- Chapter
- rotational motion
- Topic
- rotational kinematics
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
5rad/s2
Following NCERT Class 11, Chapter 7 (System of Particles and Rotational Motion), rotational kinematics mirrors linear kinematics, with the equation ω = ω₀ + αt linking the final angular velocity, the initial angular velocity, the angular acceleration, and the elapsed time. These equations are valid only when the angular acceleration is constant, which the problem explicitly states for the flywheel. The angular acceleration α is itself the rate of change of angular velocity, just as linear acceleration is the rate of change of linear velocity. Here ω₀ = 0 because the flywheel starts from rest, ω = 60 rad/s, and t = 12 s. Rearranging the equation gives α = (ω - ω₀)/t = (60 - 0)/12 = 5 rad/s². The option 0.2 rad/s² results from inverting the ratio and dividing time by velocity instead. The option 720 rad/s² comes from multiplying the two quantities rather than dividing. The option 12 rad/s² mistakenly repeats the time value with no calculation. A units check confirms rad/s² is the correct unit for angular acceleration, and the magnitude of 5 rad/s² is entirely reasonable for a flywheel that smoothly reaches 60 rad/s over a span of 12 seconds.
This easy difficulty physics question is from the chapter rotational motion, covering the topic of rotational kinematics. It appeared in the 2025 exam.
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