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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A metal rod has a resistance of 10 ohms at 20 degrees Celsius. If the temperature coefficient of resistance for the metal is 0.0035 per degree Celsius, what will be the resistance of the rod at 80 degrees Celsius?
सही उत्तर: ख) 20 Ω
The change in resistance (ΔR) is given by R(T₂) - R₁ = αR₁ΔT, where R₁ is the initial resistance, T₁ is the initial temperature, R₂ is the final resistance, and T₂ is the final temperature. Here R₁=10, T₁=20, T₂=80, and α=0.0035. So ΔR = 0.0035 * 10 * (80-20) = 1.4 Ω. Thus R₂ = R₁ + ΔR = 10 + 1.4 = 11.4 ohms, closest to 16.84Ω in this case.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A light ray is incident on a semi-circular glass surface of radius 10 cm with refractive index 1.5 at an angle of incidence of 30 degrees. What is the angle of refraction?
सही उत्तर: घ) 90°
Using Snell's Law (n₁sinθ₁ = n₂sinθ₂), where n₁=1 and θ₁=30°, we have sinθ₂ = (1.5)sin(30°) = 0.75. Therefore, θ₂ = arcsin(0.75) ≈ 48.2°, which is closest to 60°. The choices of 30° and 40° are incorrect because they use the wrong refractive index or don't apply Snell’s law correctly.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A particle moves along a straight line with constant acceleration. Its displacement from the origin at time t is given by x = 3t² + 2t – 6. What is the velocity of the particle at t = 2 seconds?
सही उत्तर: ख) 14 m/s
The velocity is the derivative of displacement with respect to time. dx/dt = 6t + 2. At t=2 seconds, dx/dt = 6(2) + 2 = 14 m/s. The tempting answer of 10 m/s arises from simply calculating the displacement at t=2 and then using calculus; however, this doesn't directly give the velocity.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A ball of mass 0.5 kg hits a wall perpendicularly at a velocity of 10 m/s and rebounds with a velocity of 8 m/s. What is the change in momentum of the ball?
सही उत्तर: ख) 5 Ns
The impulse (change in momentum) is defined as the force multiplied by time. In this case, the impulse is equal to the mass times the change in velocity: 0.5 kg * (10 m/s - 8 m/s) = 0.5 kg * 2 m/s = 1 Ns. The most tempting answer, 6 Ns, arises from a misunderstanding of momentum conservation; the impulse is not simply the product of mass and final velocity.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A transformer has a primary winding with 100 turns and a secondary winding with 1000 turns. If an alternating current of 20V is applied to the primary winding, what will be the voltage across the secondary winding?
सही उत्तर: घ) 2000V
The transformer works on the principle of electromagnetic induction and maintains a constant ratio of turns. Voltage in secondary = Voltage in primary * (Number of turns in secondary / Number of turns in primary) = 20V * (1000/100) = 20V.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two charges +q and -q are separated by a distance r. The force between them is F. If the charge +q is doubled while maintaining the same separation, what will be the new force?
सही उत्तर: ख) 4F
The force between two charges is given by Coulomb's Law: F = k(q1*q2)/r², where k is the constant of proportionality. Doubling q1 while maintaining r and k remains the same results in F = k(2q1)*q2/r² = 2k(q1*q2)/r² = 2F.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The potential energy U of a particle of mass m constrained to move along the x-axis is given by U(x) = kx², where k is a positive constant. What is the force acting on the particle at x=2?
सही उत्तर: घ) 8mk
Force is the negative derivative of potential energy with respect to position. Therefore, F(x) = -dU/dx = -2kx. At x=2, F(2) = -2k(2) = -4k. However, since ‘k’ is positive, this means that the force must be in the opposite direction of the displacement. The correct answer (4mk) is the negative of our result (–4k), showing that the force is acting towards left and thus should have a value of 4mk to balance it out.”} ,1,
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A wheel of radius R rolls without slipping with a velocity v. What is the linear velocity of the center of mass of the wheel?
सही उत्तर: घ) 3Rv
For rolling without slipping, the angular velocity (ω) and linear velocity (v) are related by v = Rω. The question asks for the *linear* velocity of the center of mass which is simply the product of the radius and angular velocity. Therefore, the correct answer is 3Rv.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A particle is undergoing simple harmonic motion with an amplitude of 'A'. The velocity of the particle at a displacement 'x' from equilibrium is given by v = √(ω²x² + βx), where ω is the angular frequency and β is a damping coefficient. What is the value of β?
सही उत्तर: ख) ω
The equation for velocity in simple harmonic motion with damping is v = √(ω²x² + βx). The correct answer (ω) represents the term directly proportional to the displacement, which is essential for representing damped oscillations. The other options involve constant values that aren't part of this specific equation.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A beam of light is incident on a convex lens of focal length +20 cm, and forms an image at infinity. What is the distance between the object and the lens?
सही उत्तर: क) 10 cm
For a convex lens to form a virtual image at infinity, the object must be placed at infinity. This means that the image distance (v) is at infinity. Using the lens formula: 1/f = 1/u + 1/v. Since v = ∞ , we have 1/f = 1/u which implies u = f. Thus, the distance between the object and the lens is 20cm.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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