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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A 1 kg mass attached to a spring of force constant 100 N/m oscillates. Its time period is about:
सही उत्तर: ग) 0.63 s
T = 2π√(m/k) = 2π√(1/100) = 0.2π ≈ 0.63 s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The gravitational potential energy of a body of mass m at a height equal to the Earth's radius R above the surface is (M = mass of the Earth):
सही उत्तर: घ) −GMm/(2R)
U = −GMm/r with r = R + R = 2R.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The mass of the Earth is about 81 times that of the Moon. On the line joining their centres, the gravitational field is zero at a point whose distance from the Earth's centre is (d = Earth–Moon distance):
सही उत्तर: क) 9d/10
GM/x² = G(M/81)/(d − x)² gives (d − x) = x/9, so x = 9d/10.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A planet has 8 times the mass and 2 times the radius of the Earth. The escape velocity from its surface is:
सही उत्तर: ख) 2 times that from the Earth
vₑ = √(2GM/R) ∝ √(M/R) = √(8/2) = 2.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The acceleration due to gravity at a height equal to half the Earth's radius above its surface is (g = value at the surface):
सही उत्तर: ख) 4g/9
g′ = g R²/(R + R/2)² = g/(1.5)² = 4g/9.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A flywheel rotating at 120 rpm is brought to rest uniformly in 10 s. Its angular retardation is:
सही उत्तर: ग) 0.4π rad/s²
ω₀ = 120 × 2π/60 = 4π rad/s; α = 4π/10 = 0.4π rad/s².
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The moment of inertia of a uniform disc of mass M and radius R about a tangent lying in its own plane is:
सही उत्तर: घ) 5MR²/4
About a diameter I = MR²/4; by the parallel axis theorem I = MR²/4 + MR² = 5MR²/4.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A solid sphere rolls without slipping down an incline of 30°. Its acceleration is about (g = 10 m/s²):
सही उत्तर: क) 3.6 m/s²
a = (5/7) g sin θ = (5/7) × 10 × 0.5 ≈ 3.57 m/s².
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A solid cylinder rolls down an incline of angle θ without slipping. Its linear acceleration is:
सही उत्तर: क) (2/3) g sin θ
a = g sin θ/(1 + I/MR²) = g sin θ/(1 + ½) = (2/3) g sin θ.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 2 kg particle moves at 5 m/s along a straight line whose perpendicular distance from a point O is 3 m. Its angular momentum about O is:
सही उत्तर: ख) 30 kg m²/s
L = mvr⊥ = 2 × 5 × 3 = 30 kg m²/s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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