Physics: Physical Properties of Materials Questions for Railway & SSC CGL Exam 2018: 26th June

Dear Students,

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 90,000 seats to be filled by the valid candidates. Opportunity is here but you have to welcome it with a provident strategy. The exam will be conducted in the month of May 2018. 

रेलवे बोर्ड अपने उम्मीदवारों के लिए भव्य और प्रतिष्ठित कार्य पदों की पेशकश करता है. और हर साल ऐसा नहीं होता है कि हमें रेलवे की ओर से अधिसूचना मिलती है. लेकिन वर्तमान वर्ष 2018 आपके लिए बहुत सुखद वर्ष है क्योंकि इसमें लगभग 90,000 सीटों को वैध उम्मीदवारों द्वारा भरा जाएगा. आपके पास बहुत अच्छा अवसर है और आपको इसे एक बेहतर रणनीति से प्राप्त करना होगा. परीक्षा मई 2018 के महीने में आयोजित की जायेगी.

Q1 .The cooling by a desert cooler is based on- 
रेगिस्तानी कूलर द्वारा कूलिंग किस पर आधारित है - 
(a) Hot air replacement/गर्म हवा प्रतिस्थापन
(b) Air dehydration/हवा निर्जलीकरण
(c) Evaporative cooling/वाष्पशील शीतलन
(d) Air rehydration/हवा पुनर्जलीकरण
Show Answer
Sol. The cooling by a desert cooler is based on evaporative cooling. These coolers are also known as swamp coolers. 

Q2. Fish can survive in a frozen lake because- 
मछली एक जमी हुई झील में जीवित रह सकती है क्योंकि - 
(a) Fish are warm blooded animals/मछली गर्म खून वाली जीव हैं
(b) Fish hibernate in ice/मछली बर्फ में शीतस्वाप में होती है
(c) Water near the bottom does not freeze/तल के पास का पानी नहीं जमता है
(d) Ice is a good conductor of heat/बर्फ उष्मा की सुचालक है
Show Answer
Sol. This is because of a phenomenon is known as winter stratification in water bodies. In the winter season, the water at the top layer of water bodies will be ice cold (0°C) and are gradually frozen. But still, the bottom layers will have liquid water and maintain a temperature (4°C) which supports the life there. Thus, fishes and other aquatic animals are saved from the frozen top layer of water.

Q3. Increasing the amount of a substance does not change its- 
किसी पदार्थ की मात्रा में वृद्धि से उसकी ________ में परिवर्तन नहीं होता है.
(a) Volume / आयतन
(b) Weight / भार
(c) Mass / द्रव्यमान
(d) Density / घनत्व
Show Answer
Sol. Density of an object depends on its mass and volume. Density can be found by using the equation:
Density = Mass/Volume

Q4. At which temperature density of water is maximum? 
किस तापमान पर पानी का घनत्व अधिकतम है?
(a) 4°C
(b) 0°C
(c) –4°C
(d) –8°C
Show Answer
Sol. The mass of any substance while heating remains the same however its volume increases. Thus, its density decreases. But water exhibits an anomalous expansion on cooling and contraction on heating within a specific range of temperature. When water at 0°C is heated, it is observed that it contracts between 0°C to 4°C, i.e. volume decreases and thus density increases. The volume of water is minimum at 4°C. Hence the density of water is maximum at 4°C.

Q5. The maximum density of water is at 
पानी की अधिकतम घनत्व ______ पर है. 
(a) 373 Kelvin /373 केल्विन
(b) 277 Kelvin / 277 केल्विन
(c) 273 Kelvin /273 केल्विन
(d) 269 Kelvin /269 केल्विन
Show Answer
Sol. The density of water increases with temperature but volume decreases. At 4°C, the volume of water is low and density is maximum. Conversion of Celsius in Kelvin
K = C + 273
= 4 + 273 = 277
So, the density of water is maximum at 277 K.

Q6. Assertion (A) : An iron ball floats on mercury but gets immersed in water. 
तर्क (A): एक आयरन बॉल मरकरी पर तैरती है लेकिन पानी में डूब जाती है.

Reason (R) : The specific gravity of iron is more than that of mercury. 
कारण (R) : एक आयरन का विशिष्ट गुरुत्व मरकरी से अधिक है.
कोड :
(a) Both (A) and (R) are true and (R) is the correct explanation of (A) / (A) और (R) दोनों सत्य हैं और (R),  (A) का सही स्पष्टीकरण है.
(b) Both (A) and (R) are true but (R) is not a correct explanation of (A) / (A) और (R) दोनों सत्य हैं लेकिन (R) (A) का सही स्पष्टीकरण नहीं हैं
(c) (A) is true but (R) is false / (A) सत्य है लेकिन (R) असत्य है .
(d) (A) is false but (R) is true  /(A)  असत्य है लेकिन (R) सत्य है.
Show Answer
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 and relative density  of  iron is  greater than the relative density than water. Thus statement (A) is correct but reason (R) is incorrect.

Q7. A needle sinks in water whereas a ship made of iron floats on it because. 
एक सुई पानी में डूब जाती है जबकि लोहा से बना एक जहाज उस पर तैरता है क्योंकि-
(a) The edge of the needle is pointed / सुई का किनारा नुकीला होता है.
(b) The ship is flat / जहाज फ्लैट है
(c) The ship driver, by power flat engine /वह एक पावर फ्लैट इंजन द्वारा चलती है
(d) Specific gravity of the needle is greater than that of water displaced by it / सुई की विशिष्ट गुरुत्वाकर्षण इसके द्वारा विस्थापित पानी की तुलना में अधिक है.
Show Answer
Sol. Relative density or specific gravity is defined as a ratio of the density of a particular substance with that of water. The relative density of pure water is 1. The substance having the relative density more than 1 will sink in water. The ship is designed in such a way that its effective density (m/v) is less than the density of water, so it floats upon the water. But the density of iron needle is much larger than the water.

Q8. While lifting a bucket of water from a well, we feel that the bucket: 
एक कुएं से पानी की एक बाल्टी उठाने के दौरान, हम महसूस करते हैं कि बाल्टी:
(a) Becomes heavier above the surface of water / पानी की सतह से ऊपर भारी हो जाती है
(b) Becomes lighter above the surface of water / पानी की सतह से हल्की हो जाती है
(c) Loses stability on coming out of the water / पानी से बाहर आने पर स्थिरता खो देती है
(d) Has gained mass on coming out of water / पानी से बाहर आने पर द्रव्यमान प्राप्त करती है
Show Answer
Sol. According to the Archimedes’s principle of flotation, object appears to be heavier in the air than inside the water or they appear to be less heavy in the water. It is because water exerts an upward force on the objects immersed in it. This reduction is equal to the weight of the fluid that body displaces.

Q9. Cooling is done by- 
शीतलन किसके द्वारा किया जाता है-
(a) Flow of water/पानी का प्रवाह
(b) Release of compressed gas/संपीड़ित गैस का निवारण
(c) Cooking gas/खान बनाने की गैस
(d) Melting the solid/ठोस को पिघलाकर
Show Answer
Sol. Most of the air conditioner uses compressed gas, which can cool the room or other places.

Q10. The separation of cream from milk by churning is due to-
मंथन द्वारा दूध से क्रीम का पृथक्करण _______ के कारण होता है:
(a) Gravitational force /गुरुत्वाकर्षण बल
(b) Cohesive force / एकजुट बल
(c) Centrifugal force / अभिकेन्द्रीय बल
(d) None of the above / उपरोक्त में से कोई नहीं
Show Answer
Sol. The separation of cream from milk by churning is due to centrifugal force.

Q11. The clouds float in the atmosphere because of their low: 
बादल वायु-मंडल में उनके कम __________के कारण उड़ते है: 
(a) Temperature/तापमान
(b) Velocity/वेग
(c) Pressure/दबाव
(d) Density/घनत्व
Show Answer
Sol. Clouds form when the invisible water vapour in the air condenses into visible water droplets. They are so small that the effect of gravity on them is negligible. Thus the clouds float in the atmosphere because of their low density.

Q12. Which of the following elements was first produced artificially? 
निम्न में से कौन सा तत्व पहले कृत्रिम रूप से बनाया गया था?
(a) Neptunium /नैप्टुनियम
(b) Plutonium / प्लूटोनियम
(c) Francium / फ्रैनशियम
(d) Technetium / टेक्नेटियम
Show Answer
Sol. Technetium is a chemical element with atomic number 43. It was the first artificially produced element. Technetium was isolated by Carlo Perrier and Emilio Segre in 1937.

Q13. While floating in a sea what part of an iceberg is above the surface of the sea? 
एक समुद्र में तैरते समय एक हिमशैल का कौन सा हिस्सा समुद्र की सतह से ऊपर होता है?
(a) 1/9
(b) 1/10
(c) 1/6
(d) 1/4
Show Answer
Sol. When pure water changes into the ice at 4°C, the density of ice so formed is 1/9th of the density of water. Therefore, in pure water, 90% part of the ice must be below the surface of the water and remaining 10% part must be above the surface, Sea water has high density (salty) water but the ice formed by it is pure and not salty.

Q14. Why it is easier to swim in the sea than in a river? 
एक नदी की तुलना में समुद्र में तैरना आसान क्यों है? 
(a) The sea water is salty / समुद्र का पानी नमकीन है
(b) The sea water is deep / समुद्र का पानी गहरा है
(c) The sea water is heavier / समुद्र का पानी भारी है
(d) The sea water is lighter/ समुद्र का पानी हल्का है
Show Answer
Sol. It is easier to swim in sea water than in river because, the sea water contains salt which increases the density of water and also increases its upthrust so, the chances of sinking get reduced and one can easily swim in such water.

Q15. When a ship enters a sea from a river, what happens? 
जब एक जहाज नदी से समुद्र में प्रवेश करता है, तो क्या होता है?
(a) It rises a little / वह थोड़े ऊंचे स्तर पर आ जाता है.
(b) It remains at the same level  / उसका स्तर समान रहता है.
(c) It sinks a little /उसका स्तर थोडा कम हो जाता है.
(d) It immersed in the bottom of the sea / वह पूर्णतः समुद्र में डूब जाता है.
Show Answer
Sol. When a ship enters a sea from a river, the ship is elevated due to the higher density of salty sea water than the river.


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