विज्ञान – Science MCQ
विज्ञान – डिप्लोमा प्रवेश
Science · CTEVT Diploma Engineering Entrance · ४०५ प्रश्न
४०५ प्रश्न उपलब्ध। मोड छान्नुहोस्:
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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The heat needed to raise the temperature of 2 kg of water by 10 °C (specific heat of water = 4200 J/kg°C) is:
सही उत्तर: क) 84000 J
Q = mcΔT = 2 × 4200 × 10 = 84000 J. 42000 J is the heat for only 1 kg.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A load of 300 N is lifted using a single ideal movable pulley. The effort needed is:
सही उत्तर: घ) 150 N
A single movable pulley has a mechanical advantage of 2 (ideal), so effort = 300/2 = 150 N. A single fixed pulley would need 300 N because its MA is 1.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a lever, the effort arm is 2 m and the load arm is 0.5 m. Neglecting friction, the effort needed to lift a 400 N load is:
सही उत्तर: ख) 100 N
By the principle of moments, E × 2 = 400 × 0.5, so E = 100 N. A longer effort arm reduces the effort needed.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A machine is supplied 500 J of energy and does 400 J of useful work. Its efficiency is:
सही उत्तर: ख) 80%
Efficiency = output/input × 100 = 400/500 × 100 = 80%. Efficiency of a real machine can never exceed 100%, so 125% is impossible.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A ball is dropped from a height of 20 m. Neglecting air resistance (g = 10 m/s²), its speed just before hitting the ground is:
सही उत्तर: घ) 20 m/s
Using energy conservation, mgh = ½mv², so v = √(2gh) = √400 = 20 m/s. 400 is v², not v.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If the velocity of a moving body is doubled (mass unchanged), its kinetic energy becomes:
सही उत्तर: ख) Four times
KE = ½mv², so KE ∝ v²; doubling v gives 2² = 4 times. Momentum, not KE, would only double.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The kinetic energy of a 2 kg body moving at 10 m/s is:
सही उत्तर: ख) 100 J
KE = ½mv² = ½ × 2 × 10² = 100 J. 200 J results from forgetting the ½.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A boy lifts a 50 kg load to a height of 4 m in 10 s (g = 10 m/s²). His power is:
सही उत्तर: घ) 200 W
Work = mgh = 50 × 10 × 4 = 2000 J; Power = 2000/10 = 200 W. 2000 is the work in joules, not the power.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A stone weighs 10 N in air and 6 N when fully immersed in water. Its relative density is:
सही उत्तर: क) 2.5
Relative density = weight in air / loss of weight in water = 10/4 = 2.5. 1.67 comes from wrongly dividing 10 by 6.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A stone weighs 10 N in air and 6 N when fully immersed in water. The upthrust acting on it is:
सही उत्तर: घ) 4 N
Upthrust = loss in weight = 10 − 6 = 4 N. By Archimedes' principle this equals the weight of water displaced.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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