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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.
| 1401. |
Can kinetic energy be negative? Why? |
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Answer» Solution :KINETIC energy cannot be NEGATIVE. `E_(k)=(1)/(2)mv^(2)`. The MASS (m) of an object cannot be negative. The VELOCITY of an object can be negative. But the square of velocity `(v^(2))` cannot be negative. As mass and the square of velocity can never be negative, the kinetic energy of an object cannot be negative. |
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| 1402. |
A small thin cylindrical glass beaker having an area of cross section "6 cm"^(2) weighs 10 gwt. If floats vertically in water upto a certain depth with 10 lead shots in it, is 8 cm, how many such lead shots can be added further into it before it sinks. |
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Answer» Solution :MASS of a beaker, `m_(1)=10g` The no. of LEAD shots = 10 The mass of each lead shot = 2 g `:.` the mass of total lead shots = 20 g `:.` the total mass of the beaker and the lead shots = 30 g `:.` the VOLUME of water displaced by the beaker with 10 lead shots in it = `30cm^(3)` area of cross section of the beaker, `a=6cm^(2)` total length of the beaker, l = 8 cm `:.` total volume of the beaker `6xx8=48 cm^(3)` `:.` volume of the beaker above the water surface `=48-30=18cm^(3)` if the beaker has to sink in water, the total beaker should be immersed in water. `rArr18cm^(3)` of water has to be displaced further `rArr18` gwt FORCE should be further added `:.` number of lead shots that has to be added further `(18gwt)/(2gwt)=9` |
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| 1403. |
The length of the beam of a cannot balance shown in the figure is 100 cm. The pans (P and Q) and the strings used to suspend them to the beamin its edges are identical. The hook (H) that is used to lift the balance is arranged at 50.5 cm from the end of the beam where the pan Q is suspended. The pan P is used for placing the standard weights. If a customer buys 9 kg of a material using the pan, find the percentage loss in the mass. |
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Answer» Solution :The information given in the question is SHOWN in the DIAGRAM APPLYING the principle of moments, we get (9 kgwt `xx` 49.5 cm) = (x kgwt `xx` 50.5 cm) X=8.8 kgwt Hence, the loss = 9 kgwt - 8.8 kgwt = 0.2 kgwt `rArr` PERCENTAGE loss `=(0.2 kgwt)/(9 kgwt)xx100 = 2.2 %` 
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| 1404. |
A body is falling from a height h. After it has fallen a height (h)/(2), it will possess : |
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Answer» only POTENTIAL energy |
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| 1405. |
The e.m.f a cell is 1.5V. What is the energy provided by the cell to drive 0.5C of charge around the circuit? |
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Answer» Solution :`VAREPSILON=1.5 V" and "q=0.5C` `varepsilon= W"/"q , W= varepsilon XX q , " THEREFORE "W= 1.5xx0.5=0.75 J` |
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| 1406. |
What is meant by supersonic speed? |
| Answer» Solution :When the speed of any object exceeds the speed of SOUND in air (330 m `s^(-1)`) it is said to be TRAVELLING at SUPERSONIC speed. | |
| 1407. |
todeterminethe weightof asolidbodyligtherthanwater a sinker is used . The solidbody ofdensity0.5g cm^(-3) is tired tothe sinkerof volume50 cm^(3) andthecombinationsis immersed into water . Ifthe volumeof waterdisplaced is 80 cm^(3) find theweightof thebody. |
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| 1408. |
The concept of energy and its trnasformation is useful in explaining and predicting most natural phenomena.(a) What is the conceptof energy in the context of chemistry ? (b) How do we associate energy with biology ? (c ) What is the roal of energytransformations in geology ? (d) What role does energy play in life ? |
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Answer» Solution :(a) In the context of chemistry, energy in an attribute of a substance as a consequence of its ATOMIC, molecular of aggregate structure. Since a chemica transformation is accompanied by a change in one or more of these kinds of struchture, it is invariably accompanied by an increase or decrease of energy of the substances involved. (b) Energy is stored by the cells in the structures of MOLECULES of substances such as carbohydrates (including sugar), LIPIDS, and proteins which relase energy when reacted with oxygen in respiration. (c ) In geology, continental DRIFT, mountain ranges volcanoes, and earthquakes and phenomena that can be explained in termsof the Earth's interior. (d) Life exists because there is energy. All living organisms rely on an external source of energy- radiation from the Sun in case of green plants, chemical energy in some form in the case of animals to grow and reproduce. The daily 1500- 2000 Calories (6.8 MJ) recommended for a HUMAN adult are taken as as a combination of oxygen and food molecules. |
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| 1409. |
A train starts from rest and accelerates uniformly at a rate of 2 m s^(-2) for 10 s. It then maintains a constant speed for 200 s. The brakes are then applied and the train is uniformly retarded and comes to rest in 50 s. Find : (i) the maximum velocity reached, (ii) the retardation in the last 50 S, (iii) the total distance travelled, and (iv) the average velocity of the train. |
| Answer» SOLUTION :(i) 20 ` m s^(-1) ` (ii) 0.4 m `s^(-2)` (iii) 4600 m (IV) 17 .69 m `s^(-1)` | |
| 1410. |
Mathematically prove that the distance (S) travelled by an object is the average mean of initial velocity (u) and final velocity (v) having constant acceleration (a) in the direction of motion in a straight line. |
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Answer» SOLUTION :To prove `S = ½ (u+v) t` We KNOW that `(v = u + "at")` And 2 as `=v^(2) -u^(2)` `rArr 2AS =(v-u) (v+u) ( :. a^(2)-b^(2)) = (a +b) (a-b)` `rArr 2 as = (v + u)` at `2S = (v + u) t` or `S = ½ (u + v)t` `rArr (u + v)//2` is the average velocity |
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| 1411. |
energy possessed by a eagle flying in air is: |
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Answer» KINETIC |
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| 1412. |
Name different types of energy. Give the unit of energy. |
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Answer» <P> Solution :The different types of energy : Mechanical energy `(E_(p)+E_(k))`, KINETIC energy, HEAT energy, chemical energy, ELECTRICAL energy, light energy, solar energy, nuclear energy, etc.The unit of energy is the joule. |
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| 1413. |
Benny is a student of class IX in a city school but his brother John studies in class V. One day John was playing with his friends just outside the house. John had a ballon in his hands. John inflated the ballon by filling air into it. He did not tie the mouth of this air-filled ballon with a thread. John just held the mouth of the inflated ballon tightly in the downward direction (towards the ground) and released it. When the inflated ballon (containing compressed air) was released with its mouth in the downward direction, then the ballon moved upwards on its own. Benny was observing this incident vert carefully. The upward going ballon reminded Benny of the principle of working of an important device. Benny also explained everything to his younger brother. Name the device whose principle of working is demonstrated by the inflated ballon released by John? (b) Name and state the principle (or law) on which the above device works. (c) Explain and working of this device briefly. (d) Which of the Newton's laws can also be said to be involved in the working of the above device? (e) Name another device which also works on the same principle as this device. (f) What values are displayed by Benny in this episode? |
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Answer» Solution :(a) The upward moving ballon demonstrates the principle of working of a rocket. (b) The rocket works on the principle of conservation of momentum or law of conservation of momentum. According to the law of conservation of momentum: When two (or more) bodies act upon one another, their total momentum remains CONSTANT (or conserved) provided no external forces are acting. (c) The chemicals inside the rocket burn and produce high velocity blast of hot gases. These hot gases rush out through the tail nozzle of the rocket in the downward direction with tremendous speed or velocity. Although the mass of gases emitted is COMPARATIVELY small, but they have a very high velocity and hence a very large momentum. An equal momentum is imparted to the rocket in the opposite direction, so that INSPITE of its large mass, the rocket goes up with a high velocity (to balance the momentum of downward going gases). (d) Newton's third law of motion (which says: To every action there is an equal and opposite reaction). (e) Jet aeroplanes also work on the same principle as a rocket. (f) The values displayed by Benny in this episode are (i) Keen observation of happenings AROUND him (ii) Knowledge of the working of rockets and jet aeroplanes, and (iii) Desire to impart knowledge to his younger brother. |
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| 1414. |
A stone is thrown vertically up from the tower of height 25m with a speed of 20 m/s What time does it take to reach the ground ? (g=10 m//s^(2)) |
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Answer» Solution :Sign convention must be used to solve this problem. It is shown in figure. We consider the upward direction as positive and DOWNWARD direction as NEGATIVE with respect to a point of reference. In the above example the point of projection is considered as the point of reference. Then, u=20 m/s `a=g=-10 m//s^(2)` `s=h=-25 m` From equation of motion `s=ut + 1//2 at^(2)` `-25 =20 t-1//2 X 10 x t^(2)` `-25=20t -5 t^(2)` `-5=4t -t^(2)` `rArr t^(2)-4t-5=0` Solving this equation, We get, (t-5) (t+1)=0 t=5 or -1 t=5s |
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| 1415. |
If the number of teeth in the driven gear of a vehicle is less than that in its driving gear, the vehicle gains ________. |
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Answer» speed |
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| 1416. |
A current 0.2 A flows in a wire of resistance 15 Omega. Find the potential difference across the ends of the wire. |
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| 1417. |
A body, the mass and the weight of which were already determined at the Equator, is now placed at the Pole. In this context, choose the correct statement from the following: |
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Answer» MASS does not CHANGE, WEIGHT is maximum |
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| 1418. |
Define Power ? |
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Answer» Solution :The RATE at which work is DONE by a force is called power. Work done PER unit time is called power. Power = work (w) / Time (T) the SI unit of power is WATT 1 watt = 1 J per second |
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| 1419. |
Which of the following can produce longitudinal as well as transverse waves under different conditions? |
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Answer» bats |
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| 1420. |
When is it said that the object performs uniform motion? |
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Answer» Covers DIFFERENT DISTANCES in equal intervals of time. |
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| 1422. |
A stone and the earth attract each other with an equal and opposite force.Why then we see only the stone fallingtowards the earth but but not the earth rising towards the stone ? |
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| 1423. |
A pendulum clockin amuseum was foundto lose 1 minute in every24 hours . Whatcorrective measureshouldthe curator of themuseum undertake? |
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Answer» Solution :(i) correct LENGTH =(observedreading ) -(zero ERROR) ZEROERROR ispositiveif observedreadingis GREATERTHAN thecorrectlengthand negative if the observedreadingis LESS than the correctreading (ii) -1.6 mm |
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| 1424. |
The length of an inclined plane is halved and the angle of inclination is changed from 30^(@) to 60^(@). If the work done in pulling a load up the first inclined plane is 'w', then the work done in pulling the same load up the second inclined plane is |
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Answer» 2W |
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| 1425. |
A body experiences an upthrust F_(1) in river water and F_(2) in sea water when dipped up to the same level. Which is more F_(1) or F_(2)?Give reason |
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| 1426. |
For which physical quantity from the following, direction is not required to be mentioned with its magnitude ? |
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Answer» SPEED |
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| 1427. |
A ray of light passes from one medium to another medium. Refraction takes place when angle of incidence is ....................... . |
| Answer» ANSWER :B | |
| 1430. |
Two objects of different masses falling freely near the surface of moon would: |
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Answer» different acceleration |
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| 1431. |
Which of the following energy change involves frictional force?i. Potential energy to sound energyii. Chemical energy to heat energyiii. Kinetic energy to heat energyiv. Chemical energy to heat energy |
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Answer» only 3 |
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| 1433. |
Explain how sound isproduced by your school bell. |
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Answer» |
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| 1434. |
(a) Explain the terms 'crests' and 'troughs' of a wave? What type of waves consist of crests and troughs? (b) The flash of a gun is seen by a man 3 seconds before the sound is heard. Calculate the distance of the gun from the man (Speed of sound in air is 332m//s). |
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| 1435. |
The gravitational acceleration on moon is one-sixth that on the earth. A person can jump as high as 2 m on earth's surface. He can jump …………. M high on the moon's surface. |
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| 1436. |
Two conductors A and B are joined by a copper wire. State the direction of flow of electrons in each of the following cases : |
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Answer» (ii) If A is NEGATIVELY charged and B is uncharged. (iii) If A is positively charged and B is negatively charged. |
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| 1437. |
Explain in detail about the application of electromagnets. |
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Answer» Solution :Applications of electromagnets- Electromagnetism has caused a great impact on various fields such as medicine, industries, space, etc. In our day to day life , it finds application in (a) Speakers- In a speaker the electromagnet is placed in front of a permanent magnet. The permanent magnet is fixed whereas the electromagnet is mobile. As pulses of electricity pass through the coil of the electromagnet, the direction of its magnetic field rapidly CHANGES. This causes it to get attached to and repelled from the permanent magnet, thereby causingvibration. The electro magnetis attached to a cone made of plastic or paper which amplifies the SOUND and the waves REACHING our ears. (b) Maglev- Magnetic levitation trains are suspended with no support other than magnetic fields. In maglev trains two sets of magnets are used. One set to repel and push the train up off the track, and another to move the floating train ahead at a great speed without friction. The train travels along a guideway of magnets which controls the train.s stability and speed using the BASIC principles of magnets. (c) MRI SCanner- Magnetic resonance imaging is a procedure using sophisticated instruments thatwork on the principle of electromagnetism that can scan minute details of the HUMAN body. Other medical equipment such as X-rays, etc., also use this principle for their functioning . |
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| 1438. |
Complete the following sentences: Two balls, one of iron and the other of aluminium experience the same upthrust when dipped completely in water if……………………. |
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| 1439. |
From a rifle of mass 4 kg, a bullet of mass 50g is fired with an initial velocity of 35ms^(-1). Calculate the initial recoil velocity of the rifle. |
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Answer» Solution :MASS of the rifle, `M_1 =4KG` Mass of the bullet, `M_2 =50g=0.05 KG` Recoilvelocity of the rifle `=V_1` Bullet is fired with ainitial velocity `V_2= 35 m//s` Initially, the rifleis at rest , Thus its initial velocity , v=0 Total initial momentum of the rifle and bullet system `=(m_1+m_2)` V=0 Total momentum of the rifle and bullet system after firing `=m_1v_1 +m_2v_2=0.05x25=4v_1+1.75`. According to the law of conservation of momentum, Total momentum afterthe firing `=0,V_1=1.75//4=0.4375m//s`. The negative sign indicates that the rifle recoils backwards with a velocity of 0.4375 m/s. |
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| 1440. |
An object of mass 16 kg has 3200 J of kinetic energy. What will be its velocity? |
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Answer» `E_(K)=(1)/(2)MV^(2)` `therefore 3200=(1)/(2)xx16v^(2)` `therefore v^(2)=(3200)/(8) therefore v^(2)=400 therefore v=20ms^(-1)` |
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| 1441. |
A diver under water sees a bird in air, vertically above him. If the actual, height of the bird above thewater surfaceis 'h' , then does it appear at the same height 'h' to the diver ? Explain giving reasons. If mu_(w) is therefractive index of water, find theshift in thebird'sposition as observed by the diver. |
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Answer» Solution :(i) What happens to the light ray when it enters an optically denser medium from an optically rarer medium? Will the light raysentering WATER appear to come from theoriginal position? When a person observes an object in water therefractive index, `mu_(W) =("REAL DEPTH")/("apparent depth")` How does the above formula change if theperson observes the object in air from water? (ii) Shift = `h(mu_(w) -1)` |
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| 1442. |
How the mass and distance between objects affects gravitational force? |
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| 1443. |
The ball is thrown vertically upwards with a velocity of 49 m/s calculate. (i) The maximum beight to which it rises. (ii) The total time it takes to return to the surface of the earth. |
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Answer» Solution :ACCORDING to the equation of motion under gravity : `v^(2)-u^(2)=2gs` Where u= initial velocity of the BALL v=Final velocity of the ball s=Height achieved by the ball g=Acceleration due to gravity. At maximum height, final velocity of the ball is zero, i.e. v=o, u=49m/s. During upward motion, `g=9.8ms^(-2)`. LET be the maximum height attained by the ball. Henece, `0-49^(2)=2xx9.8xxh` `H=(49xx49)/(2xx9.8)=122.5m` Let be the time taken by the ball to REACH the height 122.5m, then according to the equation of motion. v=u+gt Weget `0=49+txx(-9.8)` 9.8t=49 `t=49//9.8=5s` But time of ascent=time of descent. Therefore, total time taken by the ball to return `=5+5=10s`. |
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| 1444. |
A body of mass 70kg, when completely immersed in water, dispaces 20,00cm^(3) of water. Find : (i) the weight of body in water and (ii) the relative density of material of body. |
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| 1446. |
For uniform motion : |
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Answer» the distance-TIME GRAPH is a STRAIGHT line parallel to the time axis. |
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| 1447. |
The distance time graph of a body is as shown in Figure. In which portion (i) velocity is maximum (ii) velocity is minimum (iii) velocity is zero ? |
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Answer» Solution :(i) VELOCITY = slope of distance time graph, which is maximum for the PORTION `AB`, Fig. (II) velocity = minimum in the portion `OA`, because slope of `OA` is minimum, Fig. (iii) velocity = ZERO in the portion `CD`, because slope of `CD` is zero, |
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| 1448. |
The velocity-time graph shows the motion of a cyclist. Find (i) acceleration (ii) its velocity (iii) the distance covered by the cyclist in 15 second |
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Answer» Solution :(i) From the graph, the velocity of the cyclist is uniform. So, the acceleration is O (ZERO). (ii) The velocity of the cyclist is `20 ms ^(-1).` (iii) The DISTANCE covered by the cyclist = AREA of rectangle ABCD `= AD xx AB` `= (20 ms ^(-1)) xx (15s) = 300 m` |
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| 1449. |
Whenthe studs of a screwgaugeare incontacttheposition of theheadof the screw is asshownbelowDetermine the zeroerror, |
| Answer» SOLUTION :The KNIFE -EDGE in a physicalbalanceincrease itssensitivity. | |
| 1450. |
A man of mass 30 kguses a rope of climb which bears only 450 N. What is the maximum acceleration with which he can climb safely |
| Answer» SOLUTION :`15 m//s^(2) (AS_(7))` | |