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 uniform cube of side 'a' has a mass of 2 kg. What is its moment of inertia about an axis perpendicular to one face passing through the center of the cube?
सही उत्तर: ख) 5/6 ma²
The moment of inertia for a uniform cube rotating about an axis through its center and perpendicular to one face is (1/12)m(a^2). In our case, m=2kg and a=0.5m, therefore the Moment of Inertia = (1/12)*2*(0.5)^2 = 1/6 * (0.25) kg*m² = 1/6 ma². The other answers involve incorrect calculations using different moment of inertia formulas, like those for solids of revolution.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A stone is thrown vertically upwards with an initial velocity of 20 m/s from the top of a building of height 80 meters. What is the time taken for the stone to hit the ground?
सही उत्तर: ग) 4.5 s
We can use equations of motion. First, we find the time to reach maximum height (v = 0) using v = u + at, where v=0, u=20 m/s and a=-9.8 m/s². So t = 20/9.8 ≈ 2 s. Then, from the top of the building to the ground, the distance is given by h = ut + (1/2)at², where h=80m, u=20m/s and a=-9.8 m/s². Solving for t gives t = sqrt((-h)/(a)) =sqrt(-80 / 9.8) = 4.5 seconds. The other answers are either incorrect calculations of the time to reach maximum height or an incorrect use of the distance formula.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The kinetic energy of a particle moving with velocity v is given by KE = (1/2)mv². If the velocity is increased by 20% while its mass remains constant, what is the percentage increase in kinetic energy?
सही उत्तर: घ) 80
If the velocity increases by 20%, the new velocity will be 1.2v. The new kinetic energy KE' = (1/2)(m)(1.2v)² = (1/2)mv(1.44). Therefore, the ratio of KE’ to KE is 1.44, meaning the kinetic energy increased by 44%. This makes 40% the correct answer. Calculating the percentage increase involves (KE’ - KE)/KE * 100%, so ((1.44-1)*100%) = 44%. The other options were calculated with incorrect velocity changes.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A body is projected upwards with an initial velocity of 40 m/s. What is the maximum height reached by the body? (Take g = 9.8 m/s²)
सही उत्तर: ख) 73.5 m
The maximum height is reached when the final velocity becomes zero. Using the equation v² = u² + 2as, where v=0, u=40m/s, a=-9.8m/s², and s is the maximum height. Solving for s gives us (0)² = (40)² + 2(-9.8)s, so s = 84.6 m. The most tempting incorrect answer is 62.1m as this requires a different initial velocity to achieve that height.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If a particle is moving with velocity v at an angle θ to the x-axis, what are the x and y components of its velocity?
सही उत्तर: क) x = v cosθ, y = v sinθ
The x and y components of a velocity vector are found using trigonometric functions. Specifically, the x-component is given by v * cos(θ) and the y-component is given by v * sin(θ). This represents breaking the velocity into its horizontal (x) and vertical (y) components.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A particle is subjected to a force F = (kt)i + (kt)j, where k=1 N/m is a constant. Calculate the work done by this force in moving the particle from (0, 0) to (2 m, 3 m).
सही उत्तर: क) 6 Nm
This question tests understanding of work done and vector calculus. Work is defined as the dot product of force and displacement: W = F • d. Here, W = (kt)i • (2m i + 3m j) + (kt)j • (2m i + 3m j) = 2km² + 3km². Substituting k=1 N/m, we get W=2m² + 3m² = 5m², which is equivalent to 5 Nm. The most tempting incorrect option of 6Nm comes from a mistake in applying the dot product.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two waves are given by y₁ = A sin(ωt + π/3) and y₂ = A sin(ωt - π/3). What is the phase difference between the two waves?
सही उत्तर: ख) π/3 radians
This question examines wave superposition and phase differences. The given equations represent sine waves with a common amplitude A and angular frequency ω. Comparing the terms in the arguments of the sine functions, we see that y₂ is shifted by π/3 relative to y₁. This represents a phase difference of π/3 radians. The incorrect options are based on misinterpreting how wave phases relate to their equations.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A car of mass 1000 kg is traveling at 20 m/s when it enters a circular turn with a radius of 100 meters. What is the minimum speed at which the car must enter the turn to ensure it completes the circle without slipping? (Assume g = 9.8 m/s²)
सही उत्तर: क) 10 m/s
This question tests the concept of centripetal force. The required speed can be calculated using the formula v = sqrt( (r*ω²) where ω is the angular velocity and r is the radius. The centripetal force equals mv²/r, which must equal mrω²; therefore v=sqrt(grω²). In this case, the minimum speed corresponds to the smallest possible value of omega. The correct answer is 10 m/s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A tuning fork vibrating at 440 Hz produces resonance in a pipe closed at both ends with a length of 20 cm. The speed of sound in air is 340 m/s. What is the fundamental frequency of vibration? (Note: Resonant frequencies occur at one-quarter of the standing wave length)
सही उत्तर: ख) 220 Hz
Resonance occurs when the wavelength of the sound waves equals one-fourth of the pipe's length. The fundamental frequency is determined by the speed of sound and the wavelength. Option '220 Hz' is correct because 340 m/s / (4 * 0.2m) = 220Hz.”}],
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The refractive index of glass increases from 1.5 at the blue end to 1.6 at the red end of a sodium prism. The angle of deviation of light passing through the prism will be:
सही उत्तर: ग) 60°
The change in refractive index indicates that the light undergoes more refraction as it travels through the prism, leading to higher deviation. Increasing the refractive index increases the angle of deviation. ‘30°’ is the correct answer because a greater increase in refractive indices will produce a larger deviation than the other options.”}],
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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