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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In streamline flow through a narrow tube under a fixed pressure difference, if the radius of the tube is doubled, the rate of flow becomes:
सही उत्तर: ग) 16 times
By Poiseuille's equation, volume flow rate Q = πPr⁴/(8ηl) ∝ r⁴, so doubling r gives 2⁴ = 16 times.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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When the temperature is raised, the coefficient of viscosity:
सही उत्तर: ख) rises for gases but falls for liquids
Liquid viscosity falls as cohesion weakens, but gas viscosity rises because molecular momentum transfer increases with temperature.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The excess pressure inside a spherical liquid drop of radius r and surface tension T is:
सही उत्तर: क) 2T/r
A liquid drop has only one free surface, so excess pressure = 2T/r (a soap bubble with two surfaces has 4T/r).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The height h to which a liquid of density ρ and surface tension T rises in a capillary of radius r (angle of contact θ) is:
सही उत्तर: घ) h = 2T cos θ/(rρg)
Balancing the upward surface tension force 2πrT cos θ with the weight πr²hρg gives h = 2T cos θ/(rρg).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The surface tension of a liquid generally:
सही उत्तर: ग) decreases with rise in temperature
As temperature rises, intermolecular cohesion weakens, so surface tension decreases (becoming zero at the critical temperature).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Bernoulli's theorem for a flowing ideal fluid is a consequence of the conservation of:
सही उत्तर: ख) energy
Bernoulli's equation P + ½ρv² + ρgh = constant expresses conservation of energy per unit volume of the fluid.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A body weighs 10 N in air and 8 N when fully immersed in water. The relative density of the material of the body is:
सही उत्तर: क) 5
Loss of weight = upthrust = 2 N; relative density = weight in air/loss of weight = 10/2 = 5.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In simple harmonic motion, the phase difference between the acceleration and the displacement is:
सही उत्तर: घ) π
a = −ω²x, so acceleration is always opposite to displacement, i.e. out of phase by π.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In lightly damped oscillations, the amplitude of the oscillator:
सही उत्तर: ग) decreases exponentially with time
With a damping force proportional to velocity, the amplitude decays as A₀e^(−bt/2m), i.e. exponentially.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A particle in SHM has amplitude 5 cm and angular frequency 2 rad/s. Its speed when the displacement is 3 cm is:
सही उत्तर: ख) 8 cm/s
v = ω√(A² − x²) = 2√(25 − 9) = 2 × 4 = 8 cm/s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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