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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According to Kepler's second law, the areal velocity of a planet is constant and equal to (L = angular momentum, m = mass of the planet):
सही उत्तर: क) L/(2m)
dA/dt = ½r²(dθ/dt) = L/(2m), constant because the gravitational force is central and conserves L.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The binding energy of a satellite of mass m in a circular orbit of radius r around the Earth (mass M) is:
सही उत्तर: ग) GMm/(2r)
Total energy E = −GMm/(2r); the energy needed to free it completely (binding energy) is GMm/(2r).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The centre of mass of a uniform solid right circular cone of height h lies on its axis at a distance from the base of:
सही उत्तर: ख) h/4
For a solid cone the centre of mass is at h/4 above the base (3h/4 from the apex); h/3 is for a hollow conical shell or a triangular lamina.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The centre of mass of a uniform solid hemisphere of radius R lies on its axis at a distance from the centre of its flat face of:
सही उत्तर: क) 3R/8
Summing thin circular discs gives z̄ = 3R/8 for a solid hemisphere (R/2 for a hollow hemispherical shell).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The centre of mass of a uniform semicircular disc (lamina) of radius R lies on its symmetry axis at a distance from the centre of:
सही उत्तर: क) 4R/(3π)
Integrating over semicircular strips gives ȳ = 4R/(3π) for the semicircular lamina (2R/π is for a semicircular wire).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The moment of inertia of a thin uniform rod of mass M and length L about an axis through its centre making an angle θ with the rod is:
सही उत्तर: ग) (ML²/12) sin²θ
Each element at distance x from the centre is at perpendicular distance x sin θ from the axis, so I = ∫(x sin θ)² dm = (ML²/12) sin²θ.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A solid cylinder rolls without slipping down a rough incline. The force of static friction on it acts:
सही उत्तर: घ) up the incline
Gravity tends to make the contact point slide down; friction acts up the slope and provides the torque that makes the body spin up while rolling.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The angular impulse acting on a rotating body is equal to the change in its:
सही उत्तर: घ) angular momentum
Angular impulse = ∫τ dt = ΔL, just as linear impulse equals change in linear momentum.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A pump raises 10 kg of water per second through a height of 20 m and delivers it with a speed of 10 m/s. The power of the pump is (g = 10 m/s²):
सही उत्तर: ख) 2500 W
Power = (dm/dt)(gh + v²/2) = 10 × (200 + 50) = 2500 W.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A box lies on the floor of a truck that accelerates at 2 m/s². The minimum coefficient of static friction needed for the box not to slide is (g = 10 m/s²):
सही उत्तर: ग) 0.2
Friction must provide the box's acceleration: μmg ≥ ma, so μ ≥ a/g = 2/10 = 0.2.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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