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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 401. |
We sometimes are endangered by the motion of objects around us, especially if that motion is erratic and uncontrolled as observed in a flooded river, a hurricane or a tsunami. On the other hand, controlled motion can be a service to human beings such as in the generation of hydroelectric power. Do you feel the necessity to study the erratic motion of some objects and learn to control them? |
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Answer» Solution :The disasters such as FLOOD, hurricane, tsunami, volcanic eruptions, etc. affect many people. These disasters may be predicted but cannot be controlled. `to`Electronics : Erratic/ chaotic motion of electrons in semiconductors can be precisely controlled. This has GIVEN us a range of electronic devices. `to`Nuclear power plant : Erratic motion of neutrons controlled for a controlled nuclear fission. `to` Orbiting planets, artificial satellites, weather PATTERNS, mechanical systems, laser emission. chemical REACTIONS, etc. all have been shown to exhibit chaos. Of these DIVERSE systems, we have learned to control all of those that are on smaller scale. |
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| 402. |
State Achiemes priciple. |
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| 403. |
A mercury barometer in a physics laboratory shows a 732 mm vertical column of mercury. Calculate the atmospheric pressure in pascal. [Given density of mercury , rho = 1.36 xx 10^(4) kg m^(-3) , g = 9.8 ms^(-2)] |
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Answer» <P> Solution :Atmospheric pressure in the laboratory,` P = H rho g = 732 XX 10^(-3) xx 1.36 xx 10^(4) xx 9.8` ` = 9.76 xx 10^(4) Pa "(or)" 0.976 xx 10^(5) ` Pa |
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| 404. |
Electric field lines……. From positive charge and ….. In negative charge. |
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Answer» START, start |
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| 405. |
In current electricity, a positive charge refers to,….. |
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Answer» PRESENCE of electron |
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| 406. |
The following is the distance - time table of a moving car. (a) Use a graph paper to plot the distance travelled by the car versus the time . (b) What was the car travelling at the greatest speed? ( c ) What is the average speed of the car ? (d) What is the speed between 11.25amand 11.40 am? (e) During a part of the journey , the car was forced to slow down to12 km//h. At what distance did his happen? |{:("Time",,"Distance"),(10.05 am,,0 km),(10.25 am,,5 km),(10.40 am,,12 km),(10.50 am,,22 km),(11.00 am,,26 km),(11.10 am,,28 km),(11.25am,,38 km),(11.40 am,,42 km):}| |
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Answer» (b) As the slope of distance - time graph represents speed , therefore , the line with maximum slope will represents maximum speed . As is clear from Fig , line `CD` represents maximum speed between ` 10.40 am` to `10.50 am`. ( c ) Total distance travelled from ` 10.05` to `11.40 am , s = 42 km` Total time taken , `t = 11.40 - 10.05` ` = 1 h 35 m` ` =( 95)/( 60) h` Average speed , `v_(av) = ("total distance")/("time taken") =( 42 km)/( 95// 60 h) = 26.5 km//h` (d) Between `11.25 am` and `11.40 am` , distance travelled `= 42 - 38 = 4 km` `"speed" = ("distance")/("time")= ( 4 km)/( 0.25 h) = 16 km//h` (e) Slowing down must give the car minimum speed `( = 12 km//h)` . This is represented by line `EF`. For this part, distance covered `= 11.10 - 11.00 = 10 min = (10)/(60) h = (1)/( 6) h` speed `= ("distance" )/("time") = ( 2 km)/( 1//6 h) = 12 km// h`. Thus the car was forced to slow down to `12 km //h` at distance ranging from ` 26 km` to `28 km`. |
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| 407. |
Two simple pendulums A and B have lengths 1.0 m and 4.0 m respectively at a certain place. Which pendulum will make more oscillations in 1 minute ? Explain your answer. |
| Answer» SOLUTION :A. The reason is that `Tprop sqrtl therefore`. TIME PERIOD of B is more (TWICE) than that of A. Hence A will make more oscillations (twice) in a given time, than B. | |
| 408. |
Which of the following vibrates when a musical note is produced by the cymbals in a orchestra? |
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Answer» STRETCHED STRINGS |
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| 409. |
A coke can of negligible mass is in the shape of a cylinder. Its volume is 500 ml and its base area is (100)/(3)cm^(2). A person consumes nearly 25 ml of coke for every sip. After he consumes 12 sips of the drink, what is the height of the center of gravity of the can from its base when placed vertically? If the mass of the can is not negligible, how would this answer vary? |
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Answer» Solution :(i) Find the volume and base area of the coke can from the GIVEN data. Find the CENTRE of gravity `(G_(1))`, when the coke can is filled completely with coke. Does this `G_(1)` lie at half of the height of the cylinder? Find the amount of volume of coke left after 12 sips. Find the height of the coke in the can by the formula, `h = ("volume")/("base area")` Then the centre of gravity `(G_(2))` will be equal to (h/2). If the mass of the can is not negligible, will this have its own centre of gravity? Will the position `G_(2)` shifts UPWARDS? (II) 3 cm |
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| 410. |
What is the relation between frequency (v) and time period of a sound wave ? |
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| 411. |
Kunal has just appeared in class IX examination. All this examination papers are over. But Kunal's younger brother Rakesh, who is a student of class VII, is still preparing for his final examination. Yesterday, a man entered their colony in the afternoon. This man was a 'zip-repairer'. He was shounting through a large, cone-shaoed, battery-less, amplifyig device to make announcements for getting customers for his work. The hand-held device was making his voice too loud. As Rakesh was studying for his examination, he got disturbed by the loud announcements being made by this man. Rakesh told about this noise pollution problem to his elder brother Kunal because many other students living in the colony were also preparing for their examination and must be getting disturbed in their studies. Rakesh also asked Kunal about the amplifying device being used by this man. Kunal then went out of the house and talked to the man who was making announcements. The man ummediately stopped using the device for making further announcements. Kunal also went to the security incharge at the entry gate of the colony and lodged a complaint regarding this incident. (a) What do you think was the device being used by the man to amplify his voice? (b) State the principle on which this device works. (c) Why did Rakesh get disturbed? (d) What do you think Kunal must have told the 'zip-repairer' man? (e) What complaint do you think Kunal must have lodged with the security incharge of the colony? (f) Name one very useful instrument which works on the same principle as the device discussed in this episode. For what purpose is it used? (g) What values are displayed by Kunal in this episode? |
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Answer» Solution :(a) The device being used by zip-repairing man to amplify his voice was megaphone. It is also known as loud-hailer. (b) Megaphone WORKS on the principle of 'multiple reflection of sound'. (C) Rakesh got disturbed because DUE to the noise POLLUTION caused by the use of megaphone, he could not concentrate on his studies. (d) Kunal must have told the 'zip-repairer' man that since many students of the colony are preparing for their final examinations, he should not disturb their studies by using megaphone to make the announcements. (e) Kunal must have complained to the security incharge of the colony that such unauthorised persons should not be allowed to enter the residential colony to create noise pollution and disturb their piece of mind. (f) A stethoscope works on the same principle (multiple reflections of sound) as the megaphone. A stethoscope is used by doctors to listen to the sounds produced within the human body, mainly in the heart and lungs. (g) The various values displayed by Kunal is this EPISODE are (i) Awareness of magaphone and its working (ii) Helping nature (in helping his brother and other students study in peace without any disturbance), and (iii) Social responsibility (in asking for a ban on the entry of hawkers inside the residential colony who disturb their peace). |
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| 412. |
_______are useful in studying the crystal structures. |
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| 413. |
Complete the following sentence : Bats can produce and hear ............ sound. |
| Answer» SOLUTION :ULTRASONIC | |
| 414. |
If the moon attracts the earth why does the earth not move towards the moon? |
| Answer» Solution :The earth and the moon experience equal gravitational FORCES from each other However them of the earth is much larger than the MASS of the moon. Hence, it ACCELERATION is at a rate LESSER than the acceleration THEME towards the earth. For this reason the earth does not move towards the moon. | |
| 415. |
Thebase of a rectangular glass slab of thickness 10 cm and refractive index 1.5 is silvered. A coloured spot inside the glassslab at a distance of 8 cm from thebase. Determine the position of the image formed by the mirror as observed fromthe top. |
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Answer» Solution :(i) ` mu = (R.d)/(A.d)` Determine the actual position of theink mark by using theabove RELATION. Determine theactual position of the image FORMED by theplane MIRROR. (II) ` 11. 33` CM |
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| 416. |
During total internal reflection, the energy of theincident light |
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Answer» is absorbed by thereflecting surface. |
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| 417. |
A motorcar of mass 1200 kg is moving along a straight line with auniform velocity of 90km/h. its velocity isslowed down to 18 km/h in 4 seconds by an unbalanced external force. Calculate the acceleration and change in momentum . Also calculate the magnitude of the force required. |
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Answer» SOLUTION :MASS of the motorcar ,m=1200 kg Initial velocity of the motorcar v=18km/h=5 m/s Time taken ,t=4s According to the first equation of MOTION. v=u+at 5=25+a(4) `a=-5 m//s^2` Negative sign indicate that it.s a retarding motion, i.e velocity is decreasing. Change in momentum =mv-mu=m(v-u) =1200 (5-25)=-2400 kgm/s `F=ma=1200 xx5 =-6000 N `. Acceleration of the motor car `=-5 m//s^2` Change in momentum of the motor car `=-24000 kg m^(-1)` Hence, the force REQUIRED to decrease the velocity is 6000 N . (Negative sign indicate retardation, decrease in momentum and retarding force) |
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| 418. |
A piece of wood of volume 200cm^(3) and density 0.84gcm^(-3) floats in a liquid of density 1.05gcm^(-3) (i) What volume of wood will remain above the surface of liquid? (ii) What force must be exerted on wood to keep it totally submerged? |
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Answer» Solution :Given `V=200cm^(3),rho_(s)=0.84gcm^(-3),rho_(L)=1.05gcm^(-3)` (i) Let `V.cm^(3)`be the VOLUME of wood which remains above the surface of liquid. Then submerged volumeof wood `v-V-V.=(200-V.)cm^(3)` and by the principle of floatation. Weight of wood piece = Upthrust due to submerged part of wood `200xx0.84xxg=(200-V.)xx1.05xxg` `:.V.=(200xx(1.05-0.84))/1.05` `=(200xx0.21)/1.05=40cm^(3)` (ii) When wood piece is totally submerged then Upthrust `=Vxxrho_(L)xxg=200xx1.05xxg` `=210` gf (UPWARDS) Weight of wood piece `=Vxxrho_(s)xxg=200xx0.84xxg` `=168` gf(downwards) `:.` Force to be exerted to keep the wood totally submerged = Upthrust - Weight of wood piece `=210-168=42` gf |
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| 419. |
Complete the following sentence : Ultrasound is of frequency ................ |
| Answer» SOLUTION :above 20 KHZ | |
| 420. |
Fingers are wetted at intervals when currency notes are being counted. Why? |
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| 421. |
To balancea uniform metre scale suspended at 50 cm mark, a with 200 g weight suspended from it at 20 cm mark, a weight of _________ g must be suspended at 90 cm mark. |
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| 422. |
A SONAR system fixed in a submarine operates at a frequency 50 kHz. It is moving towards a rocky hill present inside water with a speed of 432 km h^(-1) . What is the apparent frequency of sound observed at the submarine after reflection by the rocky hill ? (Take velocity of sound in water to be 1450 m s^(-1) ) |
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Answer» Solution :(i) Doppler effect , `n^(1) = ((v)/(v - v_(s))) , n^(11) = n^(1) ((v+v_(0))/(v))` (ii) Consider the TWO cases . In the first case , consider the SUBMARINE as the source and rocky hill the observer of SOUND . Calculate the frequency as heard at the rocky hill USING the experssion for apparent frequency (Doppler's effect) . The frequency of sound reflected by the rocky hill is the same as that incident on it . In the SECOND case consider the rocky hill as the source and the submarine as the observer of sound . Now find the apparent frequency of sound as heard at the submarine using the experssion for apparent frequency . (iii) 59 Hz |
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| 423. |
What is the momentum of an objectof mass m, moving with a velocity V ? |
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Answer» Solution :MASS of the object =m Velcotiy =V Momentum =Mass X velocity Momentum =mv. |
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| 425. |
One day all the students of class IX were performing physics experiments in the science laboratory. Just then, the physics teacher, Mr. Vinay, came to the laboratory with a sheet of tin weighing about half a kilogram. Mr. Vinay gathered all the students and in their presence put this sheet of tin in a big tub of water. The sheet of tin sank in water and settled at the bottom of tub. Mr. Vinay now turned to the students and asked who could transform this sheet into the simplest form (or shape) which would float in water. He allowed them to use any other required tools/materials from the laboratory for this purpose. Mohan offered to make an appropriate object from this tin sheet which could float in water and not sink. He took just half an hour to make this object. The teacher placed this object in the same tub of water. It started to float in water. The teacher was very happy. He appreciated the effort made by Mohan. (a) Why did the sheet of tin sink in water? (b) What do you think is the simplest form of object made by Mohan from this tine sheet which could float in water? (c) Why do you think the above object made from tin sheet floats in water? (d) Name two modes of transport used in rivers and seas which work on the same principle as the tin sheet object made by Mohan. (e) The tine object made by Mohan was placed, turn by turn in a tub of oil and glycerine. In which of these two liquids, the tin object will float with a greater part of it immersed inside the liquid than water and why? (f) What values are displayed by Mohan in this episode? |
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Answer» Solution :(a) The sheet of tin sinks in a water because the density of tin is greater than that of water. (b) Mohan mayhave made a water-proof box from the tin sheet (by using appropriate cutting tools and sealing materials). This hollow box made of the same tin sheet FLOATS in water. (c) The hollow tin box contains a lot of air in it. Air is a very, very high light substance. Due to the presence of a lot of air in it, the average density of tin box becomes less than the density of water. And due to less average density than water, the hollow tin box floats in water. (d) Boats and ships are the two modes of transport used in rivers and seas which float in water on the same principle as the hollow tin box made by Mohan. (e) The tin box will float with its greater part immersed in oil (than in water) because oil has a lower density than water. Due to its lower density than water, oil exerts less upward (buoyant) force on tin box due to which it will sink more in oil (than water) and then float in it. (f) The various VALUES displayed by Mohan in this episode are (i) Awareness of ARCHIMEDES' principle (ii) Knowledge of factors affecting buoyant force (like volume of solid object immersed in a liquid and density of liquid) (iii) Application of knowledge in SOLVING problems, and (iv) Accepting challenge (to do a job). |
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| 426. |
In what direction dose the huoyant force on the object immersed in a liquid act ? |
| Answer» Solution :An object immersed in a liquid EXPERIENCES BUOYANT force in the UPWARD direction. | |
| 427. |
A motorcyclist moves from position A to B at the constant speed 30 kmh^(-1), then he returns from it and comes back to original position A at the speed 20 km h^(-1), final his average speed. |
| Answer» SOLUTION :`24 KM H ^(-1)` | |
| 428. |
What is the density of water in SI units |
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| 429. |
Ammeter is connected in parallel in any electric circuit. |
| Answer» SOLUTION :FALSE CORRECT Statement : An AMMETER is CONNECTED in series with a device to measureits current. | |
| 430. |
A person holds a bundle of hay over his head for 30 minutes and gets tired. Has he done some work or not? Justify your answer. |
| Answer» SOLUTION :The work done by the person is zero. The force is APPLIED on the bundle of hay but as there is no DISPLACEMENT, the work done is zero. | |
| 431. |
The source of energy in an ecosystem is |
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Answer» sun |
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| 432. |
A body of weight 1000 N sinks in water. The weight of the liquid overflowed is 250 N. What will be the weight of the body in water? |
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| 433. |
A pair of scissors is an example of ______ order lever. |
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| 434. |
Thepurpose ofplumb linein a physicalbalance andin thehands of a masonis same . If sowhat isthatpurpose ? Ifit isabsent in a physicalbalance whathappens to themass of a bodymeasured in thebalance |
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Answer» Solution :(i) Slopeof thegraph =mass flowrate T=0 represents initial CONDITION Density `=("mass")/("volume")` `=("mass flow rate")/("volumetric flow rate")` (ii) At t=0 the vesselis empty and for`t GT 5`min, there is no increase in mass of the vessel. Whatcouldbe the reasons forthemass of the vessel to remainconstant? What doesthe inclinedline ABindicate ? (iii) 16.8kg (IV) 21 litres (V) 800 KG `m^(-3)` |
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| 435. |
Why do the marking on the hydrometer increase towards the bottom? |
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| 436. |
The density of water is 1g cm^(-3).What is its density in S.I. units? |
| Answer» Solution :S.I. UNIT of DENSITY of water = `1000K g//m^(3)` | |
| 437. |
Where do they get their energy from? |
| Answer» Solution :The GREEN plants GET energy from the SUN. | |
| 438. |
Write a note on radiation. |
| Answer» Solution :Radiation is a METHOD of HEAT transfer that does not REQUIRE particles to CARRY the heat energy. | |
| 439. |
The work done in sliding a wooden box of mass 5 kg along a friction less inclined plane of inclination 30^(@) and length 10 m is ______J. (g=10 m s^(-2)) |
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Answer» 500 |
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| 440. |
The partics are placed at stone |
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| 441. |
A rectangle glass wedge (prism) is immersed in water as shown in figure E-a. For what value of angle alpha, will the beam of light, which is normally incident on AB, reach AC entirely as shown in figure E-b. Take the refractive index of water as 4/3 and the refractive index of glass as 3/2. |
Answer» Solution :From the geometry of figure E-b it is clear that, the angle of incidence on the side BC is EQUAL to `alpha` (dotted line is a NORMAL DRAWN at the point of incidence). The ray should undergo total internal reflection to reach AC. For occurrence of total internal reflection, the value of `alpha` must be greater than the CRITICAL angle at interface of water and glass.  LET .C. be the critical angle of interface of glass and water. From the given condition `alpha gt C .......(1)` We know, `sin C=1/(n^(12))` ........(2) `n_(12)=3/2 / 4/3=9/8` From equation 2, we get `sin C=8/9 rArr C=62^(@)30^(1)` Hence `alpha` is greater than `C=62^(@)30^(1)` Let us see few activities of total internal reflection. |
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| 442. |
A bus starting from rest moves with a uniform acceleration of 0.1 ms ^(-2) for 2 minutes. Find (a) the speed acquiresd (b) the distance travelled. |
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Answer» Solution :Here, `U =0, a = 0.1 ms ^(-2),` t = 2 minute = 120 second `v = ? , s= ?` `(a) u = u + at` `= 0 + 0.1 xx 120` `= 12ms ^(-1)` `(b) s = ut + (1)/(2) at ^(2)` `= 0 xx 120 + (1)/(2) xx 0.1 xx (120) ^(2)` `= (1)/(2) xx 0.1 xx 120 xx 120` `= 720 m` (a) Speed ACQUIRED is `12 ms ^(-1)` (b) The distance TRAVELLED is 720 m. |
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| 443. |
Concave mirrors are used by dentists to examine teeth. why? |
| Answer» SOLUTION :As a dentist.s head mirror : You WOULD have seen a circular mirror attached to a band tied to the forehead of the dentist/ENT specialist. A parallel beam of light is MADE to FALL on The concave mirror, this mirror focuses the light beam on a small area of the body (such as teeth, throat etc.). | |
| 444. |
A string vibrating with a fundamental frequency of 8 Hz has tension T_(1). This string vibrates with a fundamental frequency of 15 Hz when the tension is T_(2) . Find the fundamental frequency of the string when its tension is T_(1) + T_(2) . |
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Answer» Solution :(i) Relation between frequency and tension of a stretched string . (II) `N PROP sqrtT` (III) 17 Hz |
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| 445. |
State two conditions needed for work to be done. |
| Answer» Solution :The TWO CONDITIONS are a FORCE ACTING on an object and the DISPLACEMENT of the object. | |
| 446. |
One Celsius degree is an intervalof 1 Kand zero degree Celsius is 273.15 K. |
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| 447. |
A particle moves 3 m north , then 4 m east and finally6m south . Calculate the distance travelled |
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Answer» 12 m |
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| 448. |
You are given four salt solutions W,X,Y ans X of different concentrations. W is a 20% salt solution, X is a 35% salt solution, Y is a 10% salt solution whereas Z is a 50% salt solution. When a solid suspeded from the hook of a spring balance is fully submerged in all these salt solutions, one by one, then the spring balance will show the minimum reading when the solid is immersed in: |
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Answer» SOLUTION W |
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| 449. |
What is ground connection? |
| Answer» Solution :A ground connection is a SAFETY FEATURE. The metal bodies of all electrical appliances are connected to the ground by a third wire, apart from the two wires used for electrical connection. The gound conenction wire is green in COLOUR. All the ground wires from various electrical sockets are connected TOGETHER finally to a thick copper wire, burried deep in the ground, so that excess current flows down instead of entering our body. | |
| 450. |
Fill in the following blanks with suitable words: (a) Displacement is a ………… quantity whereas distance is a ……….Quantity. (b) The physical quantity which gives both the speed and direction of motionof a body is called its ………… ( c ) A motorcyclehas a steady ......... of 3m//s^(2). This means that every .......... its .........increase by .......... (d) Velocity is the rate of change of ...........It is measured in ........... (e) Acceleration is the rate of change of ......... It is measured in ........... |
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Answer» Solution :(a) vector, scalar (b) VELOCITY (c ) ACCELERATION , speed (or velocity) , 3 m/s (d) DISPLACEMENT , m/s (e) velocity , m/`s^(2)` |
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