भौतिक विज्ञान – Physics MCQ
भौतिक विज्ञान – कृषि/वन प्रवेश
Physics · Agriculture, Veterinary & Forestry Entrance · ४२५ प्रश्न
४२५ प्रश्न उपलब्ध। मोड छान्नुहोस्:
भौतिक विज्ञान: 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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Soldiers are ordered to break step while crossing a suspension bridge to avoid:
सही उत्तर: घ) resonance
If the marching frequency matched the bridge's natural frequency, the amplitude could build up dangerously (resonance).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Ten waves pass a point in 2 s, and the distance between successive crests is 2 m. The speed of the waves is:
सही उत्तर: ग) 10 m/s
f = 10/2 = 5 Hz and λ = 2 m, so v = fλ = 5 × 2 = 10 m/s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Thunder is heard 3 s after a lightning flash is seen. Taking the speed of sound as 340 m/s, the distance of the lightning is about:
सही उत्तर: ग) 1020 m
Light arrives almost instantly, so distance = speed of sound × time = 340 × 3 = 1020 m.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Bats find their way in the dark by emitting and receiving:
सही उत्तर: ग) ultrasonic waves
Bats use echolocation with ultrasound above 20 kHz.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 0.5 kg metal block at 100 °C is dropped into 1 kg of water at 20 °C. The final temperature is 25 °C. Taking the specific heat of water as 4200 J/kg K and ignoring losses, the specific heat of the metal is:
सही उत्तर: ख) 560 J/kg K
Heat lost by metal = heat gained by water: 0.5 × c × 75 = 1 × 4200 × 5 = 21,000, so c = 21,000/37.5 = 560 J/kg K.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Light-coloured clothes are preferred in summer because they:
सही उत्तर: घ) reflect most of the heat radiation falling on them
Dark surfaces are good absorbers of radiation, while light surfaces reflect most of it.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The heat needed to convert 2 kg of water at 100 °C completely into steam at 100 °C is (latent heat of vaporisation = 2.26 × 10⁶ J/kg):
सही उत्तर: ग) 4.52 × 10⁶ J
Q = mL = 2 × 2.26 × 10⁶ = 4.52 × 10⁶ J.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In metals, heat is conducted mainly by:
सही उत्तर: ग) free electrons
The free electrons in a metal carry energy quickly from hot to cold regions, which also explains why good electrical conductors are good heat conductors.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A glass greenhouse stays warm because the glass:
सही उत्तर: क) lets in short-wavelength sunlight but blocks the long-wavelength infrared emitted inside
Plants and soil absorb sunlight and re-emit infrared, which glass does not let out easily, so heat is trapped.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The instrument used to measure the relative humidity of air is a:
सही उत्तर: घ) hygrometer
A hygrometer (for example, a wet-and-dry bulb hygrometer) measures humidity; an anemometer measures wind speed.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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