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 swimmer can swim at 2 m/s in still water and the river flows at 1 m/s. To reach the point directly opposite, he must head at an angle with the upstream direction of the river bank of:
सही उत्तर: ख) 60°
The upstream component must cancel the current: 2 cos α = 1, so α = 60° with the upstream direction of the bank (30° from the perpendicular).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A ball is projected at 20 m/s at 45° to the horizontal. At a horizontal distance of 20 m from the launch point, its height is (g = 10 m/s²):
सही उत्तर: ग) 10 m
y = x tan θ − gx²/(2u²cos²θ) = 20 − 10(400)/(2 × 400 × 0.5) = 20 − 10 = 10 m.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A body moving with initial velocity 10 m/s has a uniform acceleration of 2 m/s². The distance it travels during the 5th second is:
सही उत्तर: घ) 19 m
sₙ = u + a(n − ½) = 10 + 2(4.5) = 19 m.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A car starts from rest, accelerates at 1 m/s² and then decelerates at 2 m/s² to rest. If the whole journey takes 30 s, the maximum speed reached is:
सही उत्तर: ख) 20 m/s
v/1 + v/2 = 30 s gives 3v/2 = 30, so v = 20 m/s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two balls are thrown vertically upward from the same point with the same speed of 30 m/s, the second 2 s after the first. They meet at a height of (g = 10 m/s²):
सही उत्तर: घ) 40 m
30t − 5t² = 30(t − 2) − 5(t − 2)² gives t = 4 s (for the first ball), so the height is 120 − 80 = 40 m.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A particle moves along the x-axis with velocity v = (4t − 6) m/s. The distance (not displacement) it covers from t = 0 to t = 3 s is:
सही उत्तर: क) 9 m
v changes sign at t = 1.5 s. Distance = |∫₀^1.5 v dt| + ∫_1.5^3 v dt = 4.5 + 4.5 = 9 m (the displacement is 0).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If the units of mass, length and time are each doubled, the new unit of energy is how many times the old one?
सही उत्तर: ग) 2
[E] = [M L² T⁻²]; the new unit is 2 × 2² × 2⁻² = 2 times the old unit.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A screw gauge of least count 0.01 mm has a positive zero error of 3 divisions. A wire gives a main-scale reading of 3.5 mm and 24 circular-scale divisions. The corrected diameter is:
सही उत्तर: घ) 3.71 mm
Observed = 3.5 + 24 × 0.01 = 3.74 mm; subtracting the zero error (+0.03 mm) gives 3.71 mm.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A quantity is calculated as X = a²b³/√c. If the percentage errors in a, b and c are 1%, 2% and 4% respectively, the maximum percentage error in X is:
सही उत्तर: ग) 10%
ΔX/X = 2(1%) + 3(2%) + ½(4%) = 2% + 6% + 2% = 10%.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If the error in measuring the side of a cube is 1%, the maximum percentage error in its calculated density (mass measured exactly) is:
सही उत्तर: ख) 3%
ρ = m/a³, so Δρ/ρ = 3(Δa/a) = 3 × 1% = 3%.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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