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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The SI unit of power is Watt. One Watt is equal to:
सही उत्तर: क) 1 joule per second
A Watt is defined as one joule of energy converted per second. This matches the fundamental definition of power in the SI system. The other options represent different physical quantities (energy per unit charge, force per unit distance, electric potential).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A current of 2 A flows through a resistance of 5 Ω for 10 seconds. What is the energy dissipated in Joules?
सही उत्तर: घ) 500 J
The power dissipated (P) is given by P = I²R, where I is current and R is resistance. Therefore, P = (2)² * 5 = 20 W. The energy dissipated (E) is then E = P * t = 20 * 10 = 200 J. The other options are incorrect calculations based on different values or a misunderstanding of the power-energy relationship.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two wires made of copper have lengths L1 and L2 and diameters d1 and d2 respectively. If the resistance of the first wire is R1 and that of the second wire is R2, assuming both wires have the same resistivity ρ, then which equation correctly relates R1 and R2?
सही उत्तर: ग) R1 = (ρL1/d1) * (1/L2)
The resistance of a wire is given by R = ρL/A, where ρ is resistivity, L is length, and A is cross-sectional area. Since the wires have the same resistivity, we can write R1 = ρL1/A1 and R2 = ρL2/A2. Because d1=d2, A1=π(d1)² and A2=π(d2)², so R1 = (ρL1/d1) * (d2/π(d1)²) = (ρL1/d1) * (1/d2). The other options incorrectly manipulate the formula or assume different relationships between lengths and diameters.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A stone is dropped from the top of a building. After falling for 3 seconds, what is its velocity? (Take g = 9.8 m/s²)
सही उत्तर: ख) 29.4 m/s
The stone's acceleration due to gravity is 9.8 m/s². Using the equation v = u + at (where v is final velocity, u is initial velocity, a is acceleration, and t is time), we find that v = 0 + 9.8 * 3 = 29.4 m/s. The tempting option of 19.6 m/s incorrectly calculates the velocity considering air resistance, which isn't included in this simplified scenario.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A charged particle experiences force due to magnetic field. If it moves perpendicular to the magnetic field, what will be the magnitude of the force?
सही उत्तर: ख) F=qvBsinθ
When a charged particle moving at right angle to a uniform magnetic field experiences a force, the resultant force is zero. The correct option accurately represents this; it's a crucial aspect of electromagnetism. The other options represent forces when the particle isn’t moving perpendicular to the field.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A uniform rod of length L is placed on a horizontal surface. The coefficient of static friction between the rod and the surface is μs. What maximum angle θ can the rod make with the horizontal before it starts to slide?
सही उत्तर: ख) b) tan⁻¹(2μs)
The rod will start sliding when the frictional force is no longer able to balance the component of gravity acting along the surface. The frictional force is F = μsN, where N is the normal reaction. The component of gravity acting down the slope is mgsinθ. Therefore, μsN ≥ mgsinθ and N = mgcosθ. Substituting gives μs(mgcosθ) ≥ mgsinθ, so μs cosθ ≥ sinθ. Dividing by cosθ yields μs ≥ tanθ = tan⁻¹(2μs)
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The force acting on a particle is represented by F = (6x + 4) N, where x is in meters. What is the work done by this force when the particle moves from x = 0 to x = 2 meters?
सही उत्तर: क) a) 10 J
Work done (W) is calculated as ∫F dx. In this case, W = ∫(6x+4) dx from 0 to 2. Integrating gives: [3x² + 4x] from 0 to 2 = (3(2)² + 4(2)) - (0) = 12 + 8 = 20 Joules.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A stone is thrown vertically upwards with an initial velocity of 15 m/s from the ground level. Neglecting air resistance, what will be its maximum height?
सही उत्तर: ख) b) 33.75 meters
We can use the equation of motion: v² = u² + 2as, where v is final velocity (0 m/s at maximum height), u is initial velocity (15 m/s), a is acceleration due to gravity (-9.8 m/s²), and s is the displacement (height). Solving for s, we get s = (0² - 15²) / (-9.8) = 15/9.8 ≈ 1.53 meters. The problem states it's an entrance exam, likely needing a quick application of the equation, however, since no value is given for height, this question lacks specific options to evaluate which result is correct.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A ray of light is incident on a convex lens and forms a real image on the other side of the lens. The distance between the object and the image (o) is 20 cm, and the focal length (f) of the lens is 10 cm. What is the absolute value of the magnification (m)?
सही उत्तर: ख) b) 2
The magnification formula is m = -v/u, where v is the image distance and u is the object distance. Given o = 20 cm, f = 10 cm, and since it's a real image, v = 20cm (opposite side). So, m = -20/10 = -2. The absolute value of magnification is therefore 2.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Convex mirrors provide a wider field of view than flat mirrors. This increased visibility is particularly useful in vehicles. What property of light allows this wider field of view?
सही उत्तर: क) a) Reflection of light from a larger surface
Option (a) is correct. Convex mirrors use reflection to create a wider field of view by reflecting light from a larger area. The other options describe properties that don't contribute to this effect – refraction bends light, total internal reflection occurs at boundaries between different media, and dispersion separates white light into its colors.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
यी अभ्यास प्रश्न हुन्, आधिकारिक प्रश्न होइनन्। पाठ्यक्रम, विज्ञापन र नतिजाका लागि सम्बन्धित निकायको आधिकारिक वेबसाइट हेर्नुहोस्। उत्तरमा गल्ती भेटे प्रश्नमुनिको "टिप्पणी / गल्ती रिपोर्ट" मा लेख्नुहोस्।
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