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 uniform plank 4 m long of mass 20 kg rests horizontally on supports at its two ends. A 40 kg person stands 1 m from the left end. The reaction at the left support is (g = 10 m/s²):
सही उत्तर: ग) 400 N
Taking moments about the right support: R_L × 4 = 200 × 2 + 400 × 3 = 1600, so R_L = 400 N (and R_R = 600 − 400 = 200 N).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A lift is accelerating upward with acceleration a. A coin is dropped from the lift's ceiling. Its acceleration relative to the lift floor is:
सही उत्तर: क) g + a
Relative to the upward-accelerating lift, the coin's acceleration is g − (−a) = g + a downward (the floor accelerates up towards it).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A ball thrown vertically upward with speed u rises to a maximum height H. Its speed at height H/2 is:
सही उत्तर: क) u/√2
v² = u² − 2g(H/2) = u² − gH = u² − u²/2 = u²/2, so v = u/√2.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A particle moves in a circle with constant speed v. The magnitude of the change in its velocity after half a revolution is:
सही उत्तर: ख) 2v
After half a revolution the velocity has the same magnitude but opposite direction, so |Δv| = |v − (−v)| = 2v.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 0.5 kg ball is projected at 20 m/s at 30° above the horizontal and lands on level ground. The magnitude of the change in its momentum during the flight is:
सही उत्तर: ग) 10 kg m/s
The horizontal component is unchanged; the vertical component reverses from +u sin θ to −u sin θ, so Δp = 2mu sin θ = 2 × 0.5 × 20 × 0.5 = 10 kg m/s (downward).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A ball is thrown vertically upward with speed u and returns to the thrower. Neglecting air resistance, its average speed over the whole flight is:
सही उत्तर: घ) u/2
Total distance = 2 × u²/(2g) = u²/g and total time = 2u/g, so average speed = (u²/g)/(2u/g) = u/2 (average velocity is zero).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For a particle moving in a straight line, v² = 4x + 9 (v in m/s, x in m). Its acceleration is:
सही उत्तर: ख) 2 m/s²
Comparing with v² = u² + 2as gives 2a = 4, so a = 2 m/s² (or a = v dv/dx = ½ d(v²)/dx = 2).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The dimensional formula of the universal gas constant R (PV = nRT) is:
सही उत्तर: घ) [M L² T⁻² K⁻¹ mol⁻¹]
R = PV/(nT) = energy/(amount × temperature), so [R] = [M L² T⁻²]/([mol][K]).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The dimensional formula of the Rydberg constant R (in 1/λ = R(1/n₁² − 1/n₂²)) is:
सही उत्तर: ग) [L⁻¹]
1/λ has dimensions of inverse length and the bracket is a pure number, so R has dimensions [L⁻¹].
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The dimensional formula of Wien's displacement constant b (λₘT = b) is:
सही उत्तर: क) [M⁰ L¹ T⁰ K¹]
b = λₘ × T is a length multiplied by a temperature, so its dimensions are [L K].
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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