भौतिक विज्ञान (Physics) – Physics MCQ
भौतिक विज्ञान (Physics) – CEE प्रवेश
Physics · Medical Entrance (CEE) – Physics, Chemistry, Biology & MAT · ४०७ प्रश्न
४०७ 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 ring, a disc, a solid sphere and a hollow sphere of the same mass and radius are released together from the top of the same incline and roll without slipping. Which reaches the bottom first?
सही उत्तर: ख) Solid sphere
a = g sinθ/(1 + k²/R²); k²/R² is smallest for the solid sphere (2/5), so it has the greatest acceleration and arrives first.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two satellites revolve around the Earth in circular orbits of radii r and 4r. The ratio of their orbital speeds v₁ : v₂ is:
सही उत्तर: घ) 2 : 1
Orbital speed v = √(GM/r) ∝ 1/√r, so v₁ : v₂ = √(4r/r) = 2 : 1.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A force F = (2î + 3ĵ) N acts at a point whose position vector is r = (î + 2ĵ) m. The torque of the force about the origin is:
सही उत्तर: ग) −k̂ N m
τ = r × F = (x F_y − y F_x) k̂ = (1 × 3 − 2 × 2) k̂ = −k̂ N m.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The value of g at a small height h above the Earth's surface (h ≪ R) is equal to its value at a depth d below the surface. Then d equals:
सही उत्तर: ग) 2h
g_h = g(1 − 2h/R) and g_d = g(1 − d/R); equating them gives d = 2h.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If the radius of the Earth shrinks by 1% while its mass remains the same, the acceleration due to gravity on its surface will:
सही उत्तर: ग) increase by 2%
g = GM/R², so Δg/g = −2ΔR/R = −2 × (−1%) = +2%; g increases by about 2%.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The maximum speed with which a car can take an unbanked circular turn of radius 50 m, if the coefficient of friction between tyres and road is 0.5, is about (g = 10 m/s²):
सही उत्तर: क) 15.8 m/s
Friction provides the centripetal force: mv²/r = μmg, so v = √(μrg) = √(0.5 × 50 × 10) = √250 ≈ 15.8 m/s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A ball dropped from a height of 9 m rebounds to a height of 4 m. The coefficient of restitution between the ball and the floor is:
सही उत्तर: क) 2/3
e = v_after/v_before = √(2gh₂)/√(2gh₁) = √(4/9) = 2/3.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A body of mass m moving with speed v collides with a body of mass 3m at rest and they stick together. The fraction of the initial kinetic energy lost is:
सही उत्तर: घ) 3/4
Common velocity = mv/4m = v/4; final KE = ½(4m)(v/4)² = mv²/8, which is 1/4 of the initial ½mv², so 3/4 is lost.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A pump lifts 600 kg of water per minute to a height of 20 m. The minimum power of the pump is (g = 10 m/s²):
सही उत्तर: ग) 2 kW
P = mgh/t = 600 × 10 × 20 / 60 = 2000 W = 2 kW.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A particle moves along the x-axis under a force F = (4 − 2x) newton. The work done by the force as it moves from x = 0 to x = 3 m is:
सही उत्तर: ख) 3 J
W = ∫₀³ (4 − 2x) dx = [4x − x²]₀³ = 12 − 9 = 3 J.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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