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 wooden block of volume 1000 cm³ and density 0.6 g/cm³ floats in water. The additional mass that must be placed on it to just submerge it completely is:
सही उत्तर: ग) 400 g
Full buoyancy = 1000 g-wt, block weight = 600 g-wt, so an extra 400 g is needed.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A wire of cross-section 2 mm² supports a load of 20 kg. The stress in it is (g = 10 m/s²):
सही उत्तर: ग) 10⁸ N/m²
Stress = F/A = 200/(2 × 10⁻⁶) = 10⁸ N/m².
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A spring of force constant k is cut into three equal parts, and two of the parts are joined in parallel. The force constant of the combination is:
सही उत्तर: क) 6k
Each third has constant 3k (k ∝ 1/length); two in parallel give 3k + 3k = 6k.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A particle in SHM has amplitude 0.05 m and angular frequency 10 rad/s. The magnitude of its acceleration at an extreme position is:
सही उत्तर: घ) 5 m/s²
a_max = ω²A = 100 × 0.05 = 5 m/s².
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A seconds pendulum (period 2 s) at a place where g = 9.8 m/s² has a length of about:
सही उत्तर: ख) 0.99 m
L = gT²/4π² = 9.8 × 4/39.5 ≈ 0.99 m.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 1 kg mass attached to a spring of force constant 400 N/m oscillates on a smooth floor. Its frequency of oscillation is about:
सही उत्तर: क) 3.2 Hz
f = (1/2π)√(k/m) = 20/(2π) ≈ 3.2 Hz.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The increase in gravitational potential energy when a body of mass m is raised from the Earth's surface to a height equal to the Earth's radius R is:
सही उत्तर: ख) mgR/2
ΔU = GMm/R − GMm/2R = GMm/2R = mgR/2.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The energy required to shift a satellite of mass m from a circular orbit of radius r to one of radius 2r around a planet of mass M is:
सही उत्तर: ग) GMm/(4r)
Orbital energy is −GMm/2r; the change is −GMm/4r − (−GMm/2r) = GMm/4r.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The orbital speed of a satellite at a height equal to the Earth's radius above the surface is about (g = 9.8 m/s², R = 6400 km):
सही उत्तर: घ) 5.6 km/s
v = √(GM/2R) = √(gR/2) = √(9.8 × 6.4 × 10⁶/2) ≈ 5.6 × 10³ m/s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A planet has the same mean density as the Earth but twice its radius. The escape velocity from its surface is (vₑ = Earth's value):
सही उत्तर: ख) 2vₑ
vₑ = √(2GM/R) and M ∝ ρR³, so vₑ ∝ R√ρ; doubling R doubles vₑ.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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