भौतिक विज्ञान (Physics) – Physics MCQ
भौतिक विज्ञान (Physics) – इन्जिनियरिङ प्रवेश
Physics · Engineering Entrance – Mathematics, Physics, Chemistry & English · १,३९८ प्रश्न
१,३९८ प्रश्न उपलब्ध। मोड छान्नुहोस्:
भौतिक विज्ञान (Physics): प्रश्न र उत्तर
सही लागेको विकल्पमा थिच्नुहोस्। सही भए हरियो, गलत भए रातो देखिन्छ; ३ सेकेन्डपछि सही उत्तर र व्याख्या देखिन्छ।
सही: ० / ०
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The theoretical limits of Poisson's ratio for an isotropic material are:
सही उत्तर: ग) −1 to 0.5
Elastic theory gives −1 < σ < 0.5; for practical materials it lies between 0 and 0.5.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two wires of the same material have lengths L and 2L and radii r and 2r. Under the same load, the ratio of their extensions is:
सही उत्तर: ग) 2 : 1
ΔL = FL/(πr²Y): ratio = (L/r²) : (2L/4r²) = 1 : 1/2 = 2 : 1.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A particle in SHM, x = A sin(ωt + φ), is at x = A/2 and moving towards +x at t = 0. The initial phase φ is:
सही उत्तर: क) π/6
sin φ = 1/2 with velocity Aω cos φ > 0 requires φ = π/6 (5π/6 would make the particle move towards −x).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A simple pendulum hangs in a car moving with a constant horizontal acceleration of 7.5 m/s². With g = 10 m/s², the effective acceleration that sets its period is:
सही उत्तर: घ) 12.5 m/s²
In the car frame, g_eff = √(g² + a²) = √(100 + 56.25) = 12.5 m/s².
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A pendulum clock keeps correct time. If its pendulum length increases by 0.2% (due to heating), the clock will lose per day about:
सही उत्तर: ख) 86.4 s
T ∝ √L, so T increases by 0.1%; loss per day = 0.001 × 86400 s = 86.4 s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A particle's displacement is x = 3 sin(2t) + 4 cos(2t) (in cm). The amplitude of its motion is:
सही उत्तर: क) 5 cm
Two perpendicular-phase components combine: A = √(3² + 4²) = 5 cm.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A satellite of kinetic energy K moves in a circular orbit. The minimum additional energy needed for it to escape from the Earth's gravity is:
सही उत्तर: ख) K
In a circular orbit the total energy is −K, so raising it to zero (escape) needs an additional energy K.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A uniform rod of mass 2 kg and length 1 m rotates about a perpendicular axis through one end at 6 rad/s. Its rotational kinetic energy is:
सही उत्तर: ग) 12 J
I = ML²/3 = 2/3 kg m², so K = ½Iω² = ½ × (2/3) × 36 = 12 J.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The minimum speed with which a body must be projected vertically upward from the Earth's surface to reach a height equal to the Earth's radius R is (g = surface gravity):
सही उत्तर: घ) √(gR)
½mv² = GMm/R − GMm/(2R) = GMm/(2R) = mgR/2, so v = √(gR).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A planet has 1/8 of the Earth's mass and 1/2 of its radius. If the escape velocity from the Earth is 11.2 km/s, that from the planet is:
सही उत्तर: ख) 5.6 km/s
vₑ ∝ √(M/R) = √((1/8)/(1/2)) = 1/2, so vₑ = 5.6 km/s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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