भौतिक विज्ञान – Physics MCQ
भौतिक विज्ञान – कृषि/वन प्रवेश
Physics · Agriculture, Veterinary & Forestry Entrance · ४२५ प्रश्न
४२५ प्रश्न उपलब्ध। मोड छान्नुहोस्:
भौतिक 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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Which of the following best describes the relationship between frequency and wavelength in a wave? (a) Directly proportional; as one increases, the other decreases. (b) Inversely proportional; as one increases, the other decreases. (c) They are always equal. (d) They have no relationship.
सही उत्तर: ख) (b) Inversely proportional; as one increases, the other decreases.
Frequency and wavelength in a wave are inversely proportional – a higher frequency corresponds to a shorter wavelength, and vice-versa. This is described by the equation v = fλ, where v is velocity, f is frequency, and λ is wavelength.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The phenomenon where a metal rod heats up when exposed to sunlight is primarily due to which of the following? (a) Conduction (b) Radiation (c) Convection (d) Insulation
सही उत्तर: ख) (b) Radiation
Radiation is the correct answer as metals absorb electromagnetic radiation from sunlight, which increases their internal kinetic energy and thus heats up. Conduction involves heat transfer through direct contact, convection relies on fluid movement, and insulation reduces heat flow. The other options are incorrect because they describe mechanisms of heat transfer that don't directly explain this specific scenario.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The resistance of a copper wire is 10 ohms at 20°C. If the temperature rises to 100°C, and the temperature coefficient of resistance for copper is 0.00393 / °C (2076), what will be the new resistance?
सही उत्तर: ख) 10.40 Ω
The resistance changes according to the formula R = R₀[1 + α(ΔT)], where R is the new resistance, R₀ is the initial resistance (10 ohms), α is the temperature coefficient (0.00393 / °C), and ΔT is the change in temperature (100°C - 20°C = 80°C). R = 10[1 + 0.00393 * 80] = 10[1+ 0.3144] = 10(1.3144)= 13.144 ohms which is closest to 10.38 Ω. The other options are significantly different due to incorrect use of the formula.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The force required to move a body of mass 5kg resting on a surface with a coefficient of static friction of 0.4 is, assuming g=9.8m/s² (2076),
सही उत्तर: ख) 20 N
The force required is calculated using the formula F = μsN, where μs is the coefficient of static friction and N is the normal force. The normal force is equal to the weight of the body (mg). Therefore, F = 0.4 * 5kg * 9.8m/s² = 20 N. The other options are incorrect as they do not apply this formula correctly.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A ball is dropped from a height of 45 m. Assuming air resistance is negligible, what will be the velocity of the ball just before it hits the ground? (g = 9.8 m/s²)
सही उत्तर: ख) 12.6 m/s
We can use the equation v² = u² + 2as, where v is final velocity, u is initial velocity (0m/s), a is acceleration due to gravity (9.8 m/s²) and s is the distance (45m). Therefore, v² = 0 + 2 * 9.8 * 45 = 882. Then, v = √882 ≈ 29.7 m/s. The most appealing option, 15 m/s, is too low considering the height and gravity.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The force required to accelerate a mass ‘m’ at a uniform rate of ‘a’ in a circle of radius ‘r’ is given by:
सही उत्तर: क) ma
Newton's second law states F = ma. In this case, the net force acting on the mass is the centripetal force which is needed to maintain circular motion. The other options don't correctly represent the formula for centripetal force.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 10 kg block slides down a frictionless inclined plane with an angle of 30 degrees to the horizontal. What is the acceleration of the block?
सही उत्तर: ग) 2.55 m/s²
The acceleration (a) of the block can be calculated using Newton's second law: F = ma, where F is the force and m is the mass. The component of gravity acting down the incline is F = mgsin(θ), where θ is 30 degrees. Therefore, a = gsin(θ) = (9.8 m/s²)sin(30°) = 4.9 m/s². Option 30 m/s² is incorrect, and 0 m/s² assumes no acceleration.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following is NOT a property of sound waves?
सही उत्तर: घ) They always maintain their amplitude as they travel
Sound waves need a medium (solid, liquid, or gas) to transmit. They cannot spontaneously exist in a vacuum. Reflection, refraction, and maintaining amplitude are properties of sound; however, sound waves do not inherently *always* maintain amplitude – this is dependent on the material.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A particle moves with a uniform speed in a circular path. Which of the following statements is correct regarding its motion?
सही उत्तर: ख) It has a changing velocity but constant acceleration
The particle’s speed remains constant because it moves in a circle at a uniform rate. However, its direction is constantly changing, which results in an acceleration directed towards the center of the circle. The most tempting option (constant velocity) is incorrect because the change in direction implies acceleration.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A ball is dropped from a height. As it falls, its kinetic energy increases. What causes this increase?
सही उत्तर: घ) Change in temperature
The ball's potential energy (due to its height) is converted into kinetic energy as it falls due to the force of gravity. The other options are incorrect because they do not explain this fundamental principle of physics.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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