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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When a body collides head-on elastically with another body of equal mass at rest, the first body:
सही उत्तर: ग) Comes to rest and the second moves with the first body's initial velocity
For equal masses in a 1-D elastic collision, velocities are exchanged. Moving together happens only in a perfectly inelastic collision.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a perfectly inelastic collision, which quantity is conserved?
सही उत्तर: ख) Total linear momentum
Momentum of the system is conserved in all collisions when no external force acts. In a perfectly inelastic collision the bodies stick together and kinetic energy is lost.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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One kilowatt-hour is equal to:
सही उत्तर: क) 3.6 × 10⁶ J
1 kWh = 1000 W × 3600 s = 3.6 × 10⁶ J. The kWh is a unit of energy (not power), used in electricity bills.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A crane lifts a mass of 100 kg through a height of 10 m in 20 s. Its power is (g = 10 m/s²):
सही उत्तर: घ) 500 W
P = mgh/t = 100 × 10 × 10 / 20 = 500 W. 5000 W results from dividing the work by 2 s instead of 20 s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The work done by the centripetal force on a body moving in a uniform circular path is:
सही उत्तर: ग) Zero
Centripetal force is always perpendicular to the displacement, so W = Fs cos90° = 0. Hence the kinetic energy of the body stays constant.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The force that keeps a satellite moving in a circular orbit around the Earth is provided by:
सही उत्तर: ख) Gravitational attraction of the Earth
Earth's gravity provides the necessary centripetal force. Centrifugal force is only a pseudo force in the rotating frame, not a real force on the satellite.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For a road banked at angle θ, the ideal speed v on a curve of radius r (no friction needed) satisfies:
सही उत्तर: क) tan θ = v²/(rg)
The horizontal component of the normal force supplies the centripetal force: N sinθ = mv²/r and N cosθ = mg, giving tanθ = v²/(rg).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If θ is the angle of repose, the coefficient of static friction μ equals:
सही उत्तर: घ) tan θ
At the angle of repose, mg sinθ = μ mg cosθ, so μ = tanθ. This is also the angle of friction for the same surfaces.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 10 kg block rests on a horizontal floor with coefficient of static friction 0.5. The minimum horizontal force needed to just move it is (g = 10 m/s²):
सही उत्तर: ग) 50 N
Limiting friction f = μmg = 0.5 × 10 × 10 = 50 N, so a force just exceeding 50 N starts motion. 100 N is the normal reaction, not the friction.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A person of mass 50 kg stands in a lift accelerating upward at 2 m/s². The reading of the weighing machine is (g = 10 m/s²):
सही उत्तर: ख) 600 N
N − mg = ma, so N = m(g + a) = 50 × 12 = 600 N. 400 N would be the reading if the lift accelerated downward.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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