# Physics Questions for Railway & SSC CGL Exam 2018: 5th November 2018

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Q1. Kerosene oil floats on water because-
केरोसिन तेल पानी पर तैरता है क्योंकि-
(a) Its density is greater than the density of water / इसका घनत्व पानी के घनत्व से अधिक है
(b) Its density is less than the density of water / इसका घनत्व पानी के घनत्व से कम है
(c) Its density is equal to that of the density of water / इसका घनत्व पानी की घनत्व के बराबर है
(d) None of the above  / उपर्युक्त में से कोई नहीं
Show Answer
Ans.(b)
Sol. Kerosene oil floats on water because its density is less than the density of water.

Q2. At which temperature density of water is maximum?
किस तापमान पर पानी का घनत्व अधिकतम होता है?
(a) 4°C
(b) 0°C
(c) –4°C
(d) –8°C

Show Answer
Ans.(a)
Ans.(a)
Sol. The volume of water is minimum at 4°C. Hence the density of water is maximum at 4°C.

Q3. Why does an iron nail float on mercury while it sinks in water?
एक लोहे की कील पारे पर तैरती है जबकि वह पानी में डूब जाती है?
(a) Due to less chemical interaction of iron with mercury than it is with water / पानी की तुलना में पारा के साथ लोहे की कम रासायनिक परस्पर क्रिया के कारण
(b) Iron is heavier than water and lighter than mercury./लौह पानी से भारी है और पारे की तुलना में हल्का है.
(c) Iron has greater density than water and lesser than mercury. / लोहे का घनत्व पानी की तुलना में अधिक है और पारा से कम है.
(d) Mercury is heavier than water./ पारा पानी से भारी है.

Show Answer
Ans.(c)
Sol. An iron ball floats on mercury but gets immersed in water because the relative density of mercury is greater than the relative density of iron. However iron has a higher density than water.

Q4. ______ is the perpendicular distance between point of application of force and axis of rotation.
लगाये गये बल के बिंदु और घूर्णन अक्ष के बीच की लंबवत्त दूरी ___ है.
(a) Moment arm/आघूर्ण भुजा
(b) Moment of Inertia/जड़ता प्रवृत्ति
(c) Altitude/शीर्ष-लंब
(d) Base/आधार

Show Answer
Ans.(a)
Sol. Moment Arm is the perpendicular distance between point of application of force and axis of rotation.

Q5. Which among the following is not a unit of distance?
निम्नलिखित में से कौन सा दूरी की इकाई नहीं है?
(a) Light year / प्रकाश वर्ष
(b) Longsec/लॉन्गसेक
(c) Astronomical unit / खगोलीय इकाई
(d) Parsec/ पारसेक

Show Answer
Ans.(b)
Sol. Longsec is not the unit of distance.

Q6. The apparent weight of a person in a lift which is moving down with uniform acceleration is _______.
एक लिफ्ट में एक व्यक्ति का स्पष्ट भार जो समान त्वरण के साथ आगे बढ़ रहा है वो ________.
(a) greater than the weight when the person is stationary / स्थिर होने पर व्यक्ति के वजन से अधिक है
(b) twice the weight when the person is stationary/ स्थिर होने पर व्यक्ति के वजन से दोगुना है
(c) less than the weight when the person is stationary/ स्थिर होने पर व्यक्ति के वजन से कम है
(d) same as the weight when the person is stationary/ स्थिर होने पर व्यक्ति के वजन के बराबर है

Show Answer
Ans.(c)
Sol. The apparent weight of a person in a lift which is moving down with uniform acceleration is less than the weight when the person is stationary.

Q7. Why the needle of iron swims on water surface when it is kept gently?
पानी की सतह पर लोहे की सुई को धीरे-धीरे रखने पर वह क्यों तैरती है
(a) It will remain under the water, when it will displaced more water than its weight / यह पानी के नीचे तब तक रहेगी, जब तक यह अपने भार से अधिक पानी विस्थापित करेगी
(b) the density of needle is less than that of water / सुई का घनत्व पानी की तुलना में कम है
(c) due to surface tension / सतह तनाव के कारण
(d) due to its shape / इसके आकार के कारण
Show Answer
Ans.(c)
Sol. According to Archimedes principle and we can note that the amount of water displaced by a needle is lesser than the amount of water moved out by the needle (that is displacement of the needle). So the needle initially stays on the surface of the water and then sinks into the water. Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in the floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects (e.g. water striders) to run on the water surface. This property is caused by cohesion of similar molecules, and is responsible for many of the behaviors of liquids.
Q8. The mass of a star is two times the mass of the Sun. How it will come to an end?
एक तारे का द्रव्यमान सूर्य के द्रव्यमान का दो गुना है. यह किस रूप में समाप्त हो जाएगा?
(a) Neutron Star / न्यूट्रॉन स्टार
(b) Black hole /ब्लैक होल
(c) White Dwarf / वाइट ड्वार्फ
(d) Red Giant / रेड जायंट
Show Answer
Ans.(a)
Sol. The mass of a star which is two times the mass of the sun turns into a neutron star. A neutron star is a type of stellar remnat that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with slightly larger mass than protons. Neutron stars are very hot and are supported against further collapse by quantum degeneracy pressure due to the Pauli’s exclusion principle. This principle states that no two neutrons (or any other fermionic particles) can occupy the same place and quantum state simultaneously. A typical neutron star has mass between about 1.4 and 3.2 solar masses (Chandrasekhar Limit), with a corresponding radius of about 12 km if the Akmal-Pandharipande-Ravenhall equation of state (APR EOS) is used.
Q9. Rain drops fall from great height. Which among the following statements is true regarding it?
बारिश की बूंदें अधिक ऊंचाई से गिरती हैं. निम्नलिखित में से कौन सा कथन इस संदर्भ में सत्य है?
(a) they fall with that ultimate velocity, which are different for different droplets / वे उस वेग से गिरते हैं, जो हर बूंद के लिए भिन्न है
(b) the fall with same ultimate velocity /वह समान वेग से गिरती है
(c) their velocity increases and they fall with different velocity on the earth /उनका वेग बढ़ता है और वह भिन्न वेग से धरती पर गिरती है
(d) their velocity increases and they fall with same velocity on the earth /उनका वेग बढ़ता है और वह समान वेग से धरती पर गिरती है
Show Answer
Ans.(a)
Sol. Any mass is attracted to the Earth by the pull of gravity. Gravity accelerates all objects towards the ground at a specific rate. Without any other forces present, the speed of an object in free fall will increase the farther or longer it falls. And lastly, it depends upon the speed of the object. At low speeds the object’s resistance is directly proportional to speed, and at higher speeds the object’s resistance is proportional to its speed squared. Most objects falling through the air would be considered to be moving at a higher speed, even though that speed might not be great compared to some velocities.

Q10. On which of the following techniques photostate machine works?
निम्नलिखित में से किस तकनीक पर फोटॉस्टेट मशीन कार्य करती है?
(a) Magnetic Image-Making / चुंबकीय छवि-निमार्ण
(b) Thermal Image-Making / तापीय छवि-निमार्ण
(c) Electrostatic Image-Making / इलेक्ट्रोस्टैटिक छवि-निमार्ण
(d) Electromagnetic Image-Making / विद्युतचुंबकीय छवि-निमार्ण
Show Answer
Ans.(c)
Sol. All Electrostatic Copiers work under the premise that a charge of electricity is place on an Image Drum which has the ability to retain the electric charge much like a capacitor holds its charge but with the ability to hold or release the charge depending on how much light and darkness is applied to the Image Drum. A photocopier (also known as a copies of documents and other visual images quickly and cheaply. Most current photocopiers use a technology called xergorahpy. A dry process using heat. Copiers can also use other technologies such as ink jet, but xerography is standard for office copying.

Q11. One Kilowatt hour is equal to-
एक किलोवाट घंटा किसके बराबर है
(a) 3.6 Mega Joule / मेगाजूल
(b) 3.8 Mega Joule / मेगाजूल
(c) 3.2 Mega Joule / मेगाजूल
(d) 4.0 Mega Joule / मेगाजूल
Show Answer
Ans.(a)
Sol. The energy 1 kilowatt-hour (kWh) is 3600000 joules or 3.6 mega joule. In physics, energy is an indirectly observed quantity that is often understood as the ability of a physical system to do work on other physical systems. However, this must be understood as an overly simplified definition, as the laws of thermodynamics demonstrate that not all energy can perform work.
Q12. Atmospheric pressure is measured by __________.
वायुमंडलीय दबाव __________ द्वारा मापा जाता है.
(a) Barometer/बैरोमीटर
(b) Hexameter/हेक्सामीटर
(c) Nanometer/नैनोमीटर
(d) Glaxometer/ग्लाक्सोमीटर
Show Answer
Ans.(a)
Sol. Atmospheric pressure is measured by Barometer.

Q13. Instrument for measuring rainfall is called
वर्षा को मापने वाले उपकरण को क्या कहा जाता है?
(a) Lucimeter/लुसिमीटर
(b) Galactometer/गलाक्टोमीटर
(c) Hyetometer/ह्येटोमीटर
(d) Hygrometer/हाइग्रोमीटर
Show Answer
Ans.(c)
Sol. Hyetometer is the instrument used to measure rainfall.
Q14. Who established the foundations of the quantum theory?
क्वांटम सिद्धांत की नींव किसने स्थापित की?
(a) Max Planck/मैक्स प्लैंक
(b) Mark Nicholas/मार्क निकोलस
(c) Albert Einstein/अल्बर्ट आइंस्टीन
(d) Alfred Hitchcock/अल्फ्रेड हिचकॉक
Show Answer
Ans.(a)
Sol. Max Planck was a German theoretical physicist, considered to be the initial founder of quantum theory, and one of the most important physicists of the 20th Century.
Q15. If in a motion, the axis of the rotation passes through an object, the motion is called
_________.
यदि एक गति में, घृणन का अक्ष वस्तु के माध्यम से गुजरता है, तो गति को __________ कहा जाता है.
(a) Orbital motion / कक्षीय गति
(b) Circulatory motion/ परिसंचरण गति
(c) Spin motion/ घृणन गति
(d) Oscillatory motion/ दोलन गति
Show Answer
Ans.(c)
Sol. In physics, spin is the velocity of rotation of something around a particular axis.

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