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 soap film (surface tension 0.03 N/m) on a wire frame is enlarged from 10 cm × 6 cm to 10 cm × 10 cm. The work done is:
सही उत्तर: क) 2.4 × 10⁻⁴ J
A film has two surfaces, so W = 2TΔA = 2 × 0.03 × (0.010 − 0.006) = 2.4 × 10⁻⁴ J.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Water (density 1000 kg/m³, viscosity 10⁻³ Pa s) flows at 0.1 m/s through a pipe of diameter 2 cm. The Reynolds number of the flow is:
सही उत्तर: घ) 2000
Re = ρvD/η = 1000 × 0.1 × 0.02/10⁻³ = 2000.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Eight identical rain drops, each falling with terminal velocity v, merge into one drop. The terminal velocity of the big drop is:
सही उत्तर: क) 4v
The radius doubles (volume ×8), and terminal velocity ∝ r², so it becomes 4v.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Water fills a tall tank to height H. A small hole is made in its side at depth h below the surface. The jet strikes the ground farthest from the tank when:
सही उत्तर: ग) h = H/2
Range = v × t = √(2gh) × √(2(H − h)/g) = 2√(h(H − h)), which is greatest when h = H/2.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A pressure of 76 cm of mercury is equal to about:
सही उत्तर: घ) 1.013 × 10⁵ Pa
P = hρg = 0.76 × 13600 × 9.8 ≈ 1.013 × 10⁵ Pa (one standard atmosphere).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A uniform rod of length L, density ρ and Young's modulus Y hangs vertically from one end. The extension produced by its own weight is:
सही उत्तर: क) ρgL²/(2Y)
The tension at distance x from the free end is ρAgx; integrating ρgx dx/Y from 0 to L gives ρgL²/(2Y).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A steel rod is clamped rigidly at both ends and heated through 50 K. With Y = 2 × 10¹¹ N/m² and α = 1.2 × 10⁻⁵ K⁻¹, the thermal stress developed is:
सही उत्तर: ग) 1.2 × 10⁸ N/m²
The prevented strain is αΔT, so stress = YαΔT = 2 × 10¹¹ × 1.2 × 10⁻⁵ × 50 = 1.2 × 10⁸ N/m².
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A wooden cylinder floats upright in water with a length h submerged. If it is pushed down slightly and released, it oscillates with period:
सही उत्तर: ख) 2π√(h/g)
An extra depth x gives a restoring force ρ_w A g x, and the mass is ρ_w A h (equal to the displaced water), so ω² = g/h.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A particle is subjected to two perpendicular SHMs x = A sin ωt and y = A cos ωt. Its path is:
सही उत्तर: ख) a circle of radius A
x² + y² = A²(sin²ωt + cos²ωt) = A², which is a circle of radius A.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A uniform rod of length L pivoted at one end swings as a compound pendulum. For small oscillations its period is:
सही उत्तर: ख) 2π√(2L/(3g))
T = 2π√(I/(mgd)) with I = mL²/3 and d = L/2, which gives 2π√(2L/(3g)).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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