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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The relation between escape velocity (vₑ) and orbital velocity (v₀) of a satellite close to the Earth's surface is:
सही उत्तर: ख) vₑ = √2 v₀
v₀ = √(gR) and vₑ = √(2gR), so vₑ = √2 v₀. Hence increasing a near-surface satellite's speed by about 41% would let it escape.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The acceleration due to gravity at the centre of the Earth is:
सही उत्तर: क) Zero
Inside the Earth g' = g(1 − d/R), which becomes zero at d = R. g is maximum at the surface, not at the centre.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The acceleration due to gravity at a height equal to the radius of the Earth (R) above its surface is:
सही उत्तर: घ) g/4
g' = g R²/(R + h)² = g R²/(2R)² = g/4. g/2 is a common mistake from assuming linear variation with distance.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The escape velocity of a body from the Earth does NOT depend on:
सही उत्तर: ग) The mass of the body
vₑ = √(2GM/R) contains only the planet's mass and radius, not the mass of the escaping body. A heavier body needs more energy but the same speed.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A ball moving with velocity v collides head-on elastically with an identical ball at rest. After the collision:
सही उत्तर: क) The first ball stops and the second moves with velocity v
In a one-dimensional elastic collision between equal masses, the velocities are exchanged. Moving together at v/2 happens only in a perfectly inelastic collision.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a perfectly inelastic collision, which of the following is conserved?
सही उत्तर: घ) Linear momentum only
Linear momentum is conserved in every collision with no external force, but in a perfectly inelastic collision the bodies stick together and kinetic energy is lost. Both are conserved only in an elastic collision.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A spring of spring constant 200 N/m is stretched by 0.1 m. The elastic potential energy stored is:
सही उत्तर: ग) 1 J
U = ½kx² = ½ × 200 × 0.01 = 1 J. 2 J results from omitting the factor ½.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If the linear momentum of a body is doubled, its kinetic energy becomes:
सही उत्तर: ख) Four times
K = p²/2m, so doubling p multiplies K by 2² = 4. Doubling the speed has the same effect since K ∝ v².
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The work done by the centripetal force on a body in uniform circular motion is:
सही उत्तर: क) Zero
Centripetal force is always perpendicular to the displacement, so W = Fs cos90° = 0. That is why the speed (kinetic energy) remains constant.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The working of a rocket is based on the conservation of:
सही उत्तर: घ) Linear momentum
Gases expelled backward carry momentum, and the rocket gains equal and opposite momentum. It does not need air to push against, which is why it works in space.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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