Beats used for: MCQ with Answer and Explanation
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Question #1
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An artificial satellite orbits Earth in a circular path. If its orbital radius is increased, its orbital velocity:
Correct Answer: Option D
Explanation:
Orbital velocity v = √(GM/r), where r is orbital radius from Earth's center. Thus v ∝ 1/√r. If r increases, v decreases. This follows from equating gravitational force to centripetal force: GMm/r² = mv²/r ⇒ v = √(GM/r). Higher orbits have slower speeds but longer periods. Memory aid: 'Higher orbit, slower speed' – counterintuitive but fundamental. This relationship is crucial for satellite motion questions in competitive exams. Always distinguish orbital velocity from escape velocity (which is √2 times orbital velocity at same radius).
Orbital velocity v = √(GM/r), where r is orbital radius from Earth's center. Thus v ∝ 1/√r. If r increases, v decreases. This follows from equating gravitational force to centripetal force: GMm/r² = mv²/r ⇒ v = √(GM/r). Higher orbits have slower speeds but longer periods. Memory aid: 'Higher orbit, slower speed' – counterintuitive but fundamental. This relationship is crucial for satellite motion questions in competitive exams. Always distinguish orbital velocity from escape velocity (which is √2 times orbital velocity at same radius).
Question #2
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A photon of energy 3.3 eV has frequency approximately (h=4.14×10⁻¹⁵ eV s)
Question #3
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A vernier caliper has 20 divisions on vernier scale matching 19 main scale divisions. If main scale division is 1 mm, least count is:
Correct Answer: Option B
Explanation:
Least count = 1 MSD - 1 VSD. 20 VSD = 19 MSD ⇒ 1 VSD = 19/20 mm = 0.95 mm. LC = 1 - 0.95 = 0.05 mm. Formula: LC = MSD/n where n = vernier divisions. Memory tip: LC = smallest measurable difference = main scale value/vernier divisions. Essential for practical physics questions in competitive exams.
Least count = 1 MSD - 1 VSD. 20 VSD = 19 MSD ⇒ 1 VSD = 19/20 mm = 0.95 mm. LC = 1 - 0.95 = 0.05 mm. Formula: LC = MSD/n where n = vernier divisions. Memory tip: LC = smallest measurable difference = main scale value/vernier divisions. Essential for practical physics questions in competitive exams.
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