Railway Board offers opulent and revered job posts to its aspirants. And it is not every year that we get the notification from Railway offering a good number of vacant seats to the multitude aspirants. But the current year 2018 brought a pleasant surprise with almost 1,27,278 seats to be filled by the valid candidates. Opportunity is here but you have to welcome it with a provident strategy.
किस क्रिया द्वारा नम कपड़ों को स्पिन ड्रायर में सुखाया जाता है?
(a) centripetal forces / अभिकेन्द्रीय बल
(b) centrifugal forces/ अपकेन्द्रीय बल
(c) central forces/ केंद्रीय बल
(d) non-central forces/ अकेंद्रीय बल
Sol. Centrifugal force is an outward force apparent in a rotating reference frame. It does not exist when a system is described relative to an inertial frame of reference. Damp clothes are dried in spin dryers by the action of centrifugal forces.
Q2. The atmospheric air is held to the earth by
वायुमंडलीय वायु किसके द्वारा पृथ्वी जुड़ी रहती है?
(a) gravity/ गुरुत्वाकर्षण
(b) winds/ पवन
(c) clouds/ बादल
(d) rotation of the Earth/ पृथ्वी का घूर्णन
Sol. The atmospheric air is held to the earth by the force of gravity which holds down the atmosphere. The atmospheric air molecules cannot escape the gravitational pull of the Earth as the escape velocity on the Earth’s surface is 11.2 km/s. At the moon’s surface the value of escape velocity is 2.38 km/s so there is no any atmosphere around the moon.
Q3. The minimum number of geostationary satellites needed for uninterrupted global coverage is
निर्बाध वैश्विक कवरेज के लिए आवश्यक भूस्थिर उपग्रहों की न्यूनतम संख्या है
(a) 3
(b) 2
(c) 4
(d) 1
Sol. Minimum three geostationary satellites are needed for the uninterrupted global coverage.
Q4. If the velocity-time graph of a particle is represented by y = mt + c, then the particle is moving with
यदि एक कण का वेग-समय ग्राफ y = mt + c द्वारा दर्शाया गया है, तो कण ____ गति से गतिशील है।
(a) constant speed/ स्थिर गति
(b) constant velocity/ स्थिर वेग
(c) constant acceleration/ स्थिर त्वरण
(d) varying acceleration/ परिवर्तनशील त्वरण
Sol. If the velocity-time graph of a particle is represented by y = mt + c, then the particle is moving with constant acceleration.
Q5. A particle dropped from the top of a tower uniformly falls on ground at a distance a which is equal to the height of tower. Which of the following paths will be traversed by the particle?
एक कण को एक टावर के शीर्ष से एकसमान गति से जमीन पर दूरी a पर गिरता है जो टॉवर की ऊंचाई के बराबर है। निम्नलिखित में से कौन से पथ कण द्वारा अपनाया जाता है?
(a) circle / वृत्त
(b) Parabolic/ परवलयिक
(c) Great circle/ ग्रेट सर्कल
(d) Hyper-parabolic/ हाइपर-पैराबोलिक
Sol. If a particle is dropped from the top of a tower uniformly falls on ground at a distance which is equal to the height of tower then a parabolic path will be traversed by a particle because when the particle is dropped that point is called the point of projection and when it reaches the ground that point is called the point of impact. Now, if the two points is met with one another the curve emerges is parabolic in nature. Hence, we can say that the path followed by the particle is of parabolic trajectories.
Q6. A sphere rolls down on two inclined planes of different angles but same height, it does so
एक गोला विभिन्न कोणों की लेकिन समान ऊंचाई की दो झुकी हुई सतहों पर लुढ़कती है, इसमें ऐसा होता है:
(a) in the same time/ समान समय में
(b) with the same speed/ समान गति के साथ
(c) in the same time with the same speed/ समान गति के साथ समान समय में
(d) in the same time with the same kinetic energy/ समान समय में समान गतिज ऊर्जा के साथ
Sol. The velocity of the sphere at the bottom depends on height and acceleration due to gravity.Both these values are constant.Therefore the velocity at the bottom remains the same from whichever inclined plane the sphere is rolled
Q7. For which of the following substances, the resistance decreases with increase in temperature?
निम्नलिखित में से किस पदार्थ के लिए, तापमान में वृद्धि के साथ प्रतिरोध कम हो जाता है?
(a) Pure silicon/ शुद्ध सिलिकॉन
(b) Copper/ कॉपर
(c) Nichrome/ निक्रोम
(d) Platinum/ प्लेटिनम
Sol. Pure silicon resistance decreases with increase in temperature.
Q8. A transformer works on the principle of
एक ट्रांसफार्मर किसके सिद्धांत पर काम करता है?
(a) self induction/ सेल्फ इंडक्शन
(b) mutual induction/ पारस्परिक प्रेरण
(c) generator / जनरेटर
(d) inverter/ इन्वर्टर
Sol. A transformer consists of two electrically isolated coils and operates on Faraday’s principal of “mutual induction”, in which an EMF is induced in the transformers secondary coil by the magnetic flux generated by the voltages and currents flowing in the primary coil winding.
Q9. In AC circuits, AC meters measure
एसी सर्किट में, एसी मीटर क्या मापता है?
(a) mean values/ माध्य मान
(b) rms values/ आरएमएस मान
(c) peak values/ शिखर मान
(d) mean square values/ माध्य वर्ग मान
Sol. In AC circuits, AC meters measure rms values.
Q10. When the milk is churned vigorously, the cream from it separated out due to
जब दूध का जोर से मंथन किया जाता है, तो उसमें से क्रीम किस कारण से अलग हो जाता है?
(a) gravitational force/ गुरुत्वाकर्षण बल
(b) frictional force/ घर्षण बल
(c) centrifugal force/ अपकेन्द्रीय बल
(d) centripetal force/ अभिकेन्द्रीय बल
Sol. When the milk is churned vigorously the cream from it is separated out duel the effect of centrifugal force as when liquids of different specific gravities revolve around the same distance and with the same angular velocity, then a huge centrifugal force is exerted on the heavier than on the lighter one.
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