Work done by centripetal force in circular motion is: MCQ with Answer and Explanation

Work done by centripetal force in circular motion is:
A. Zero
B. Depends on radius
C. Positive
D. Negative
Answer: Option A
Solution (By JKSSB Mock Tests)
Centripetal force acts radially inward, perpendicular to tangential displacement. Work W = F·d·cosθ; θ=90° ⇒ cos90°=0 ⇒ W=0. No energy transfer occurs; speed remains constant in uniform circular motion. Memory tip: 'Perpendicular force ⇒ zero work'. Conceptual question testing work-energy understanding, common in competitive exams to identify misconceptions about circular motion.

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Practice More Physics Questions

Question #1
The dimension of Planck's constant is same as that of
A. Angular momentum
B. Linear momentum
C. Energy
D. Force

Correct Answer: Option A


Explanation:
Planck's constant h = E/ν, so its dimensions are [Energy]/[Frequency] = [ML²T⁻²]/[T⁻¹] = [ML²T⁻¹]. Angular momentum = mvr = M·LT⁻¹·L = [ML²T⁻¹]. Energy = [ML²T⁻²], linear momentum = [MLT⁻¹], force = [MLT⁻²]. Thus, Planck's constant and angular momentum share dimensions. This is a key dimensional match in quantum mechanics.

This question belongs to: Science Physics
Question #2
The working of a refrigerator is based on
A. Heating effect of current
B. Evaporation and condensation of refrigerant
C. Photoelectric effect
D. Magnetic effect

Correct Answer: Option B


Explanation:
Refrigerant evaporates inside absorbing heat, compressed outside releasing heat, cycle repeats.

This question belongs to: Science Physics
Question #3
The phenomenon of diffraction limits the resolving power of optical instruments because:
A. Atmospheric turbulence distorts light
B. Mirrors reflect imperfectly
C. Light bends around edges, causing image blurring
D. Lenses absorb light

Correct Answer: Option C


Explanation:
Diffraction causes light waves to spread when passing through apertures or around obstacles, creating Airy patterns instead of point images. This fundamental wave effect limits the minimum resolvable detail (Rayleigh criterion: θ_min ≈ 1.22λ/D). Options B, C, D are practical limitations but not the fundamental diffraction limit. Memory tip: 'Diffraction limit: smaller λ or larger aperture ⇒ better resolution'. This wave optics concept is frequently tested in competitive exams. Always distinguish fundamental limits (diffraction) from technical limitations (aberrations, turbulence) in instrument performance.

This question belongs to: Science Physics