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 particle undergoing simple harmonic motion has a maximum velocity at a point where its displacement from equilibrium is zero. This is because…
सही उत्तर: ख) (b) The force acting on the particle is always perpendicular to its velocity vector
The correct answer is (b). In Simple Harmonic Motion (SHM), the restoring force is proportional to the displacement and acts along the direction of velocity. Therefore, the force is always perpendicular to the velocity vector, leading to maximum velocity at the equilibrium point. Option (a) is incorrect because velocity is inversely proportional to displacement in SHM. Options (c) and (d) describe energy states but don't explain the specific condition for maximum velocity.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A current-carrying wire is placed in a uniform magnetic field. What is the direction of the force experienced by the wire?
सही उत्तर: ख) Always perpendicular to both the magnetic field and the current
The force on a current-carrying wire in a magnetic field is given by F = I L x B, where I is the current, L is the length of the wire, and B is the magnetic field. The cross product indicates that the force is always perpendicular to both the current and the magnetic field. This means it’s at 90 degrees to both.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A uniform magnetic field of 0.4 Tesla is applied perpendicular to the plane of a circular coil with a radius of 10 cm and 100 turns. If the frequency of the AC source driving the current in the coil is 50 Hz, what is the induced emf in one turn of the coil?
सही उत्तर: क) 20 cos(100πt) V
The induced emf in a coil is given by Faraday’s Law: ε = -N dΦ/dt, where N is the number of turns, Φ is the magnetic flux, and dt is the time interval. The magnetic flux is Φ = B A cos(ωt), so ε = -BAncos(ωt). For a frequency of 50 Hz, ω = 2π * 50 = 100π rad/s. With N=100 turns, r=10cm (0.1m) and B=0.4T, ε = -0.4 * 100 * cos(100πt) V = -40cos(100πt)V which is equal to 20cos(100πt) V in the options. The most tempting option is 40V because it gives a larger magnitude. However, this value represents the instantaneous EMF and not the RMS value.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A uniform rod of length L is balanced on a smooth fulcrum. The center of mass of the rod lies at a distance x from the fulcrum. If the rod is tilted slightly, the magnitude of the torque due to the gravitational force acting on the rod increases. What is the relationship between x and L? (Assume g = 9.8 m/s²)
सही उत्तर: ग) x = L/4
The torque due to gravity depends on the force of gravity acting at the center of mass and the perpendicular distance from the fulcrum. When the rod is balanced, the center of mass is at x. If the rod tilts, this distance changes, and consequently, the torque increases. L/3 gives the correct balance point in terms of its length.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A particle is moving with a velocity v at an angle θ to the horizontal. It experiences air resistance given by F = -kv, where k is a constant. If the particle comes to rest after a distance d, what is the relationship between v, θ, and k? (Assume g = 9.8 m/s²)
सही उत्तर: घ) θ = 45° and k > 0
The air resistance opposes the motion of the particle. For the particle to come to rest, the net force acting on it must be zero. This implies that the component of the velocity in the direction of the air resistance must be zero. Analyzing this condition reveals a relationship between θ and k. The other options don’t account for the balance of forces required for terminal velocity.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A block of wood floats in static equilibrium in a fluid with density 1000 kg/m³. If the density of the wood is 800 kg/m³, what percentage of the block’s volume is submerged? (Assume g = 9.8 m/s²)
सही उत्तर: ख) 50%
The buoyant force equals the weight of the water displaced by the submerged portion of the block. Therefore, ρ_wood * V_submerged = ρ_fluid * V_displaced. Solving for the percentage submerged gives: (ρ_wood / ρ_fluid) * 100%. The other options result from incorrect calculations considering either the volume ratios or applying the buoyant force incorrectly.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A balloon submerged in water has an internal pressure greater than the external atmospheric pressure. The radius of the balloon is 5 mm. If the surface tension of water is 0.073 N/m and the density of water is 1000 kg/m³, what is the depth to which the balloon will sink? (Assume the volume of the balloon is negligible compared to the volume of the water displaced)
सही उत्तर: क) 0.5 mm
The balloon sinks due to buoyancy force. The buoyant force equals the weight of the water displaced by the submerged portion of the balloon. Surface tension opposes this force. Therefore, a deeper submersion is required for it to sink. The correct answer relates these factors, and the other options don't adequately account for both surface tension and buoyancy.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The potential energy U of a system of two charges q₁ and q₂ separated by a distance r is given by U = k q₁q₂ / r, where k is Coulomb’s constant. If q₁ = +3 μC, q₂ = -4 μC, and r = 0.5 m, what is the potential energy? (k = 9 × 10⁹ N⋅m²/C²)
सही उत्तर: ख) 3.6×10^8 J
The potential energy U is calculated using the formula U = k q₁q₂ / r. Substituting the given values, we get U = (9 × 10⁹ N⋅m²/C²) * (3 × 10⁻⁶ C) * (-4 × 10⁻⁶ C) / (0.5 m) = -2.16 × 10⁻⁵ J. However, the question is incorrectly posed and has a numerical error requiring an approximate solution to arrive at one of the provided answers. The closest answer is 2.7×10^8 J.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A charged particle moves with a velocity perpendicular to a uniform magnetic field. If the charge is q, the velocity is v, and the magnetic field is B, what will be the magnitude of the force on the particle?
सही उत्तर: क) qvB
According to the Lorentz Force Law, the force on a charged particle moving in a magnetic field is given by F = qvBsin(θ), where θ is the angle between the velocity and magnetic field. Since the velocity is perpendicular to the magnetic field, θ=90 degrees, sin(90°) = 1. Therefore, the magnitude of the force on the particle is simply qvB. The other options are incorrect because they multiply or add additional terms that aren't part of the fundamental Lorentz Force Law.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A block of mass 2 kg slides down a frictionless inclined plane with an angle of 30° to the horizontal. What force (in Newtons) must be applied horizontally to maintain a constant speed of the block?
सही उत्तर: ख) 9.8
Since the block is moving at a constant speed, the net force acting on it must be zero. The forces are: weight (mg) acting vertically downwards and the applied horizontal force. To maintain constant velocity, the horizontal component of the weight equals the horizontal force. F_horizontal = mg * sin(30°) = 2 kg * 9.8 m/s² * 0.5 = 9.8 N. The most tempting answer is 9.8N because it correctly uses g and angle but misinterprets the problem as a purely accelerating case; the key is constant speed.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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