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 simple pendulum with a bob of relative density 8 has period T in air. When the bob swings fully immersed in water (ignoring viscosity), its period becomes about:
सही उत्तर: घ) 1.07 T
Buoyancy reduces the effective g to g(1 − σ/ρ) = 7g/8, so T′ = T√(8/7) ≈ 1.07 T.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Taking the Earth's rotation into account, the effective acceleration due to gravity at latitude λ is:
सही उत्तर: ग) g − ω²R cos²λ
The centrifugal effect has a component ω²R cos²λ along the radius, which subtracts from g; it is greatest at the equator and zero at the poles.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Three particles, each of mass m, are placed at the corners of an equilateral triangle of side a. The gravitational potential energy of the system is:
सही उत्तर: ग) −3Gm²/a
There are three pairs, each contributing −Gm²/a, so U = −3Gm²/a.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If a straight tunnel were dug through the Earth along a diameter, a body dropped into it would perform SHM with a period of about (R = 6400 km, g = 9.8 m/s²):
सही उत्तर: घ) about 85 minutes
Inside a uniform Earth g ∝ distance from the centre, so T = 2π√(R/g) ≈ 5.08 × 10³ s ≈ 84.6 min.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The period of a satellite revolving in a circular orbit around the Earth:
सही उत्तर: ग) does not depend on the mass of the satellite
T = 2π√(r³/GM) contains only the orbital radius and the Earth's mass, not the satellite's mass.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Because of the Earth's rotation, the effective value of g at the equator is less than it would be without rotation by about (R = 6400 km):
सही उत्तर: ग) 0.034 m/s²
The reduction is ω²R = (7.27 × 10⁻⁵)² × 6.4 × 10⁶ ≈ 0.034 m/s².
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For a wheel rolling without slipping with centre speed v, the speed of the topmost point relative to the ground is:
सही उत्तर: क) 2v
The top point has translational velocity v plus rotational velocity ωR = v in the same direction, giving 2v.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A thin uniform rod of length L stands vertically on a frictionless pivot at its lower end and falls over. The speed of its upper end just before it hits the floor is:
सही उत्तर: क) √(3gL)
Loss of PE mgL/2 = ½(mL²/3)ω², so ω = √(3g/L) and the tip speed is ωL = √(3gL).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A solid sphere rolling without slipping on a level floor with speed v reaches the foot of an incline and rolls up it. The greatest height it reaches is:
सही उत्तर: घ) 7v²/(10g)
Total KE = ½mv²(1 + 2/5) = 7mv²/10 = mgh, so h = 7v²/(10g).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The moment of inertia of a uniform rectangular plate of mass M and sides a and b about an axis through its centre perpendicular to its plane is:
सही उत्तर: ख) M(a² + b²)/12
Using the perpendicular axis theorem: I = Ma²/12 + Mb²/12 = M(a² + b²)/12.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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