40048 + Interview Questions in Physics in Class 11

1.	The static friction does not depend upon
Answer» the area of contact normal force the MAGNITUDE of APPLIED force NONE of the above Solution :the area of contact

Discussion

2.	Micrometer is used to measure dimension of molecule of oleic acid by monomolecular laye method.
Answer» ANSWER :FALSE. MICROSCOPE is USED.

Discussion

3.	A metal tape gives correct measurement at 15^(@) C. Tt is used to measure a distance of 100 m at 45^(@) C. The error in the measurement, if alpha = 12 xx 10^(-6) // 1^(@) C 1 is
Answer» 36cm 36m 42 MM 36 mm ANSWER :D

Discussion

4.	lf the distance between the source & absorber is halved then Intensity of radiant energy will be
Answer» DOUBLED Quadrupled HALVED increased to 16 TIMES ANSWER :B

Discussion

5.	A bullet, on penetrating two successive wooden planks of unequal thickness loses its velocity by 200 "m.s"^(-1) in each case. If the initial velocity of the bullet is 1000 "m.s"^(-1)calculate the acceleration after 2 seconds.
Answer» ANSWER :`9:7`

Discussion

6.	Energy released by th explosion of supernova is 10^(44) J , then express it in electron volt unit .
Answer» SOLUTION :`6.25 xx10^(60) EV `

Discussion

7.	Two holes are made on the wall and at the bottom of a cylindrical vessel. Now the two holes are closed with two corks and the vessel is filled with water. If the vessel is now allowed to fall under gravity and the two holes are opened during its flight, then state what will happen.
Answer» SOLUTION :We know that a BODY falling freely under gravity experiences weightlessness. So, the vessel filled with water REMAINS weightless while it is falling under gravity. Then, the upper layers of the LIQUID exert no pressure on the LOWER layers and hence there is no pressure difference in the vessel. As a result, no water will come out through the two holes.

Discussion

8.	Water rises to height h' in capillary tube .If the length of capillary tube above the surface of water is made less than 'h' then ……..
Answer» WATER does not rise at all . water rises upto the tip of capillary TUBE and then starts overflowing like a fountain. water rises upto the top of capillary tube and stays there without overflowing . water rises upto a POINT a little below the top and stays there. Answer :C

Discussion

9.	Which of the following units could be associated with a vector quantity ?
Answer» NEWTON/metre newton metre/second `KG m^(2)s^(-2)` newton second Answer :D

Discussion

10.	Obtain the formula of acceleration of a particle from the formula of displacement of SHM.
Answer» Solution :ACCELERATION of SHM particle is TWO times differentiation of displacement w.r.t. to time of particle OR Acceleration of SHMf particle is the differentiationl of velocity of particle w.r.t. time. The displacement of SHM particle at time t, `x(t)= A cos (omega t+ phi)` Differentiating with time t, `v(t)= -A omega sin (omega t+phi)` Again differentiating with time t, `a(t) = -A omega^(2) cos (omega t+ phi)` `therefore a(t)= -omega^(2) x(t) """..........."(1)` `[therefore -A cos (omega t+phi)= x(t)]` generally `a= -omega^(2) x`. Special cases : (1) At mean position x(t)=0, `a= -omega^(2) xx 0` `therefore a= 0` Acceleration at mean position is zero and velocity is maximum. (2) At extreme points, `x(t)= \|A\|` `a= -omega^(2) \|A\|` `therefore a= omega^(2)A" or "a= -omega^(2)A` Hence, at extreme points acceleration is maximum is called `a_("MAX")` `therefore a_("max")= A omega^(2)` Acceleration in +x-direction is negative and in -x-direction it is POSITIVE.

Discussion

11.	At what angle the vector (vec(A)+vec(B)) and (vec(A)-vec(B)) must act, so that the resultant is sqrt(A^(2)_B^(2))
Answer» `COS^(-1)((A^(2)-B^(2))/(A^(2)+B^(2)))` `cos^(-1)((A^(2)+B^(2))/(A^(2)-B^(2)))` `cos^(-1)((A^(2)-B^(2))/(2(A^(2)+B^(2))))` `cos^(-1)((A^(2)+B^(2))/(2(B^(2)-A^(2))))` ANSWER :D

Discussion

12.	A piece of wood of mass 0.3 kg is dropped from the top of a building 100 m high. At the same time a bullet of mass 0.2 kg is fired vertically upward with a velocity of 100 ms^(-1) from the ground. The bullet gets embedded in the wooden piece after striking. find the height which the combination rises above the biolding before it starts falling
Answer» 46.5 m 41.6 m 49.7 m 52.3 m Answer :B

Discussion

13.	If a body of mass 0.98 kg is made to oscillate on a spring of force constant 4.84 N/m, the angular frequency of the body is
Answer» `1.22 "rad/sec"` `2.22 "rad/sec"` `3.22 "rad/sec"` `4.22 "rad/sec"` ANSWER :B

Discussion

14.	Two waves of wavelength 99cm and 100cm both travelling with the velocity of 396ms^(-1) are made to interfere. Calculate the number of beats produced b then per sec.
Answer» Solution :`lamda_1 = 99 CM = 0.99 cm` `lamda_2 = 100 cm = 1m ` Velocity of SOUND WAVES in a gas is ` v = 396ms^(-1)` Relation between wavelength and velocity `v = lamda f` ` THEREFORE ` Frequency corresponding to ` lamda_1 , f_1 = (v)/(lamda_1) = (396)/(0.99) , f_1 = 400 Hz` Frequency corresponding to `lamda_2 , f_2 =396 Hz` Number of beats PER second ` \|f_1 - f_2\| = 400 -- 396` n = 4 beats per sec

Discussion

15.	Mark the correct statement with respect to escape speed
Answer» Escape speed is independent of the direction in which it is PROJECTED The rotational EFFECT of earth plays a role in computation of escape speed, however SMALL it may be A body THROWN in EASTWARD direction is having less escape speed All the above Answer :D

Discussion

16.	A body has mechanical energy but no momentum, or has momentum but no mechanical energy -is it possible ?
Answer» Solution :A body at rest at a height from the ground has potential ENERGY, a form of MECHANICAL energy, but no momentum. A body with momentummust have some VELOCITY and thus some KINETIC energy associated with it. Since kinetic energy is a form of mechanical energy, a body with momentum must have some mechanical energy .

Discussion

17.	The pressure of a gas does not depend up on
Answer» KINETIC ENERGY of its MOLECULES The temperature of GAS The density of the gas The volume of the gas when the density remains unchanged ANSWER :D

Discussion

18.	The volume of one mole of an ideal gas with adiabatic exponent gammais varied according to V=b/T,where b is a constant. Find the amount of Heat is absorbed by the gas in this process temperature raised by DeltaT
Answer» `((1-gamma)/(gamma+1))RDeltaT` `R/(gamma-1)DeltaT` `((2-gamma)/(gamma-1))RDeltaT` `(RDeltaT)/(gamma-1)` Solution :`V=b/T RARR T=b/V`…(1) `PV=muRT` `=(muRb)/V` `THEREFORE PV^2=muRb`=constant Now for adiabatic CHANGE `PV^x` =constant by comparing it x=2 Now, `c=R/(gamma-1)+R/(1-x)` `=R/(gamma-1)+R/(1-2)` `=R/(gamma-1)-R` `=R[(1-gamma+1)/(gamma-1)]=R[(2-gamma)/(gamma-1)]` HEAT absorbed `DeltaQ=muCDeltaT` here `mu=1` mole `therefore DeltaQ=RDeltaT((2-gamma)/(gamma-1))`

Discussion

19.	If the formula for a physical quantity is W=(a^(4)b^(3))/(c^(2)sqrt(d)) and if percentage errors in the measurement of a, b, c and d are 1%, 2%, 3% and 4% respectively. Find the percentage error in W.
Answer» 1% 16% 18% 12% Solution :`(DELTAW)/(W)=4(Deltaa)/(a)+3(Deltab)/(h)+2(DELTAC)/(2)+(1)/(2)(Deltad)/(d)` `=4(1%)+3(2%)+(1)/(2)(4%)` 18%

Discussion

20.	Suppose that the rotation of the earth was increased such that the centripetal acceleration was equal to the gravitational acceleration at the equator (i) Find the speed of a person standing at the equator and (ii) How long would a day be ?
Answer» Solution :`v^(2)//r =G, v= sqrt(rg) = sqrt(6400 xx 10^(3) xx 9.8) = 7.9 km//s, T = 2pir//v = 2PI xx 6400 xx 10^(3)//7.9 xx 10^(3) = 5070 s`

Discussion

21.	Name three important discoveries of Physics, which have revolutionised modern chemistry.
Answer» SOLUTION :(i) STUDY of radioctivity (ii) Study of isotopes by mass spectrographs (iii) X-ray DIFFRACTION etc.

Discussion

22.	At what height should a rope of length x be tiedto a long vertical pole so that a person standing on the ground can pull down the pole by applying a force F at the other end of the rope most conveniently?
Answer» ANSWER :`(X)/(SQRT(2))`

Discussion

23.	Assertion : A solid is floating in a liquid . If temperature is increased and expansion of solid is ignored, then fraction of volume immersed will increase. Reason : By increasing the temperature density of liquid will decrease.
Answer» If both ASSERTION and REASON are CORRECT and Reason is the correct explanation of Assertion. If both Assertion and Reason are true but Reason is not the correct explanation of Assertion. If Assertion is true but Reason is false. If Assertion is false but Reason is true. Solution :N//A

Discussion

24.	The value of 42 xx 0.041 with due regard to significant figures is
Answer» 1.722 1.72 1.7 1.8 Answer :C

Discussion

25.	what would be the duration of the year if the distance between the earth and the sun gets doubled?
Answer» 1032 625 365 129 Answer :a

Discussion

26.	ML^(-1)T^(-2) represents
Answer» Stress Young's modulus Pressure all the above Answer :D

Discussion

27.	A lead bullet of unknown mass is fired with a speed of 180 ms^(-1) into a tree in which it stops. Assuming that in this process two third of heat produced goes into the bullet and one third into wood. The temperature of the bullet raises by (Specific heat of lead = 0.12J g^(-1) ""^(@)C^(-1))
Answer» `140 ""^(@)C` `106 ""^(@)C` `90 ""^(@)C` `100 ""^(@)C` ANSWER :C

Discussion

28.	The time period of a body suspended from a spring is T. The new time period if it is cutting to three equal parts and same mass suspended for one part , the new time period is
Answer» `SQRT(2)T` `sqrt(3)T` `T/(sqrt(2))` `T/(sqrt(3))` ANSWER :D

Discussion

29.	The force of gravitation is .........
Answer» REPULSIVE conservative electrostatic NON - conservative Solution :`implies` Gravitational FORCE is a conservative just LIKE electrostatic force.

Discussion

30.	The valuve of force constant between the applied elastic force F and displacement with be
Answer» `SQRT(3)` `(1)/(sqrt(3))` `(1)/(2)` `(sqrt(3))/(2)` ANSWER :2

Discussion

31.	In fig.1.21 load-elongation of two wires made of two different materials A and B are shown. The wires have the same length and the same area of cross section. Which material has a greater value of Y?
Answer» SOLUTION :For the same load F, ELONGATIONS in the wires made of MATERIALS A and B are `l_1` and `l_2` respectively [Fig.1.21] Since their initial LENGTHS are the same, `(longitudi nal strai n)_Alt(longitu d i nal STRA i n)_B`. Now, `Y=(longitudi nal stress)/(longitudi nal strai n)` Hence, `Y_A gt Y_B`.

Discussion

32.	From a complete ring of mass.m. andradius .R. a30° sector is removed. The M.I. of the remaing ring about an axis through centre of ring and normal to its plane is:
Answer» `3/4 MR^(2)` `11/12 mR^(2)` `2/5mR^(2)` `mR^(2)` ANSWER :B

Discussion

33.	In a faulty barometer some air occupying the space over mercury column. How can the air pressure be correctly determined with this faulty barometer?
Answer» SOLUTION :LET the length of mercury column =`h_1`, and that of air column over mercury `=l_1` now the barometer tube is raised a little still keeping the OPEN END dipped into mercury. Let in this case,the length of mercury column=`h_2`, and that of air column over mercury `=l_2`. If the true reading of the air pressure is H, and the area of cross section of the tube is a, then from Boyle.s LAW `(H-h_1)l_1a=(H-h_2)l_2aor,H=(h_1l_1-h_2l_2)/(l_1-l_2)` Hence, measuring `h_1,h_2,l_1,l_2` the correct atmospheric pressure can be find out.

Discussion

34.	Give three properties which have different magnitudes and also have different direction.
Answer» SOLUTION :THERMAL CONDUCTIVITY, ELECTRIC conductivity and COMPRESSIBILITY.

Discussion

35.	What are longitudinal and transverse waves ?
Answer» Solution : ITIS because TRANSVERSE waves TRAVEL in the form of crests and troughs which involves the change in shape. For the PROPAGATION of transverse waves, medium should posses elasticity shape. Therefore transverse waves are not PRODUCED in gases.

Discussion

36.	A uniform chain of length L and mass M is lying on a smooth table and one third of its length is hanging vertically down over the edge of the table. If g is acceleration due to gravity, work required to pull the hanging part on to the table is
Answer» `MGL` `(MgL)/2` `(MgL)/9` `(MgL)/18` ANSWER :D

Discussion

37.	A person in an elevator accelerating upwards with an acceleration of 2 ms^(2) tosses a coin vertically upwards with a speed of 20ms^(-2) After how much time will the coin fall back into his hand ? (g = 10 ms^(-2)).
Answer» Solution :Here, `U=20 ms^(-1) , v = 0` Effective acceleration , ` a = - (g + a) = - (10 + 2) = - 12 m//s^(2)` If t is time of eacent of the coin, then from `upsilon = u + "at"` `0 = 20 - 12 t, t = (20)/(12) = (5)/(3)s` Time of descent = time of ASCENT ` = (5)/(3)s ` `:.`Total time after which the coin will fall black into HAND ` = (5)/(3) + (5)/(3) = (10)/(3)s = 3.33s` .

Discussion

38.	Time period of mars to revolve around Sun is 8 times greater than that of Mercury. If distance of Mercury from Sun is 5.79xx10^10 m then that of Mars is approximately …... .
Answer» ANSWER :`23.16xx10^10m` TIME PERIOD `T PROPR^(3/2)` `:.T_"Mars"/T_"Mercury"=(r_"Mars"/r_"Mercury")^(3/2)` `:.(8)^(2/3)=r_"Mars"/r_"Mercury"` `:.4=r_"Mars"/(5.79xx10^10)` `:.r_"Mars"=4xx5.79xx10^10` `=23.16xx10^10m`

Discussion

39.	If a body is projected with angle theta to the horizontal, then ·
Answer» its velocity is always perpendicular to its acceleration. its velocity BECOMES zero at its MAXIMUM height. its velocity makes zero angle with the horizontal at its maximum height. the body just before hitting the fround, the DIRECTION of velocity COINCIDES with the acceleration. Answer :C

Discussion

40.	A ball of mass m , moving with a speed 2v_(0) collides inelastically ( e gt 0) with an identicalball at rest . Show that (a) For head - on collision , both the balls move forward . (b) For a general collision , the angle between the two velocities of scattered balls is less than 90^(@)
Answer» Solution :(a) Let `v_(1) and v_(2)` are velocities of the two balls after collision . From law of CONSERVATION of linear momentum , `2mv_(0)=mv_(1)+mv_(2)` ` :. 2v_(0) =v_(1)+v_(2)` and `e= (v_(2)-v_(1))/(2v_(0)) rArr v_(2)=v_(1) +2v_(0)e` ` :. 2v_(1)=2v_(0)-2ev_(0)` ` :. v_(1)=v_(0)(1-e)` Since , `e lt 1 rArr v_(1)` has the same sign as `v_(0)` therefore , the ball moves on after collision . (b) Consider the diagram below for general collision . From the law of conservation of linear momentum , `P=P_(1)+P_(2)` For inelastic collision some KE is lost , hence `(p^(2))/(2m)gt(p_(1)^(2))/(2m)+(p_(2)^(2))/(2m)` `p^(2)gt p_(1)^(2)+p_(2)^(2)` THUS , p,`p_(1) and p_(2)` are related as shown in the FIGURE. `theta` is acute (less than `90^(@)`) `(p^(2)=p_(1)^(2)+p_(2)^(2) "WOULD be given if " theta =90^(@))`

Discussion

41.	A child sits stationary at one end of a long trolley moving uniformly with a speed V on a smooth horizontal floor. If the child gets up and runs about on the trolley in any manner, what is the speed of the CM of the (trolley + child) system?
Answer» System REMAINS UNCHANGED INCREASE decreases increases or decrease Answer :A

Discussion

42.	Check the correctness of the equation 1/2 mv^(2) = mgh using dimensional analysis method.
Answer» Solution :Dimensional formula for `1/2 MV^(2) = [M][LT^(-1)]^(2) = [ML^(2)T^(-2)]` Dimensional formula for MGH = `[M][LT^(-2)][L] = [ML^(2)T^(-2)] ` `[ML^(2)T^(-2)] = [ML^(2)T^(-2)]` Both SIDES are dimensionally the same, hence the equations `1/2 mv^(2)` = mgh is dimensionally correct.

Discussion

43.	Which of the followingquantities remain constant in a planetory motion (consider elliptical orbits) as seen from the sun ?
Answer» SPEED ANGULAR speed KINETIC ENERGY angular momentum Answer :D

Discussion

44.	………. vecF .vecs scalar quantity
Answer» SOLUTION :WORK DONE

Discussion

45.	A particle executes simple harmonic motion between X=-A and X=+A. The time taken for it to go from 0 to A/2is T_1 and to go from A/2 is T, then:
Answer» `T_1 LT T_2` `T_1 GT T_2` `T_1 = T_2` `T_1 = 2T_2` ANSWER :A

Discussion

46.	barF=abari+3barj+6 bark and bar r=2bari-6 barj-12 bark. The value of a. for which the angular momentum is conserved is
Answer» `-1` 0 1 2 Answer :A

Discussion

47.	(A) : A body can have acceleration even if its velocity is zero at a given instant of time. (r) : A body is momentarily at rest when it reverses its direction of motion.
Answer» Both (A) and (R) are true and (R) is the correct EXPLANATION of (A) Both (A) and (R) are true and (R) is not the correct explanation of (A) (A) is true but (R) is false Both (A) and (R) are false Answer :A

Discussion

48.	The escape velocity for a planet is v_e. A particle starts from rest at a large distance from the planet, reaches the planet only under gravitationa attraction, and passes through a smooth tunnel through its centre. Its speed at the centre of the planet will be
Answer» `v_e` `1.5 v_(E )` `sqrt(1.5)v_(e )` `2v_(e )` ANSWER :C

Discussion

49.	If I is the moment of inertia and E is the kinetic energy of rotation of a body, then its angular momentum will be
Answer» `SQRT((EI))` `2 EI` `E//I` `sqrt((2EI))` Solution :As `E = (1)/(2) I omega^(2) = (1)/(2) (I^(2) omega^(2))/(I) = (L^(2))/(2I) therefore L= sqrt(2 EI)`

Discussion

50.	A ball is projected with velocityd of 20sqrt(2) m/s at an angle of 45^(@) with horizontal and at the same instant another plate is rotating with constant angular velocity omega=(pi)/(4) rad/sec in vertical plane as shown in the figure ( assume the length of plate is sufficient for collision to take place). If the mass of the plate is much larger than the mass of the ball, the plate is initially in horizontal position and collisionis perfectly elastic, then choose the correct statement (s)
Answer» Time when the ball collides with the plate is 2 (SI unit) velocity of the ball just after collision with the plate is `10(2+pi)`(SI unit) Distance of ball when it again collides on the ground surface from the projection point is `20PI`(SI unit) Maximum height ACHIEVED by the ball is 20 (SI unit) Answer :A::B::C::D

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

The static friction does not depend upon

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A metal tape gives correct measurement at 15^(@) C. Tt is used to measure a distance of 100 m at 45^(@) C. The error in the measurement, if alpha = 12 xx 10^(-6) // 1^(@) C 1 is

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Water rises to height h' in capillary tube .If the length of capillary tube above the surface of water is made less than 'h' then ……..

Which of the following units could be associated with a vector quantity ?

Obtain the formula of acceleration of a particle from the formula of displacement of SHM.

At what angle the vector (vec(A)+vec(B)) and (vec(A)-vec(B)) must act, so that the resultant is sqrt(A^(2)_B^(2))

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The pressure of a gas does not depend up on

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Suppose that the rotation of the earth was increased such that the centripetal acceleration was equal to the gravitational acceleration at the equator (i) Find the speed of a person standing at the equator and (ii) How long would a day be ?

Name three important discoveries of Physics, which have revolutionised modern chemistry.

At what height should a rope of length x be tiedto a long vertical pole so that a person standing on the ground can pull down the pole by applying a force F at the other end of the rope most conveniently?

Assertion : A solid is floating in a liquid . If temperature is increased and expansion of solid is ignored, then fraction of volume immersed will increase. Reason : By increasing the temperature density of liquid will decrease.

The value of 42 xx 0.041 with due regard to significant figures is

what would be the duration of the year if the distance between the earth and the sun gets doubled?

ML^(-1)T^(-2) represents

A lead bullet of unknown mass is fired with a speed of 180 ms^(-1) into a tree in which it stops. Assuming that in this process two third of heat produced goes into the bullet and one third into wood. The temperature of the bullet raises by (Specific heat of lead = 0.12J g^(-1) ""^(@)C^(-1))

The time period of a body suspended from a spring is T. The new time period if it is cutting to three equal parts and same mass suspended for one part , the new time period is

The force of gravitation is .........

The valuve of force constant between the applied elastic force F and displacement with be

In fig.1.21 load-elongation of two wires made of two different materials A and B are shown. The wires have the same length and the same area of cross section. Which material has a greater value of Y?

From a complete ring of mass.m. andradius .R. a30° sector is removed. The M.I. of the remaing ring about an axis through centre of ring and normal to its plane is:

In a faulty barometer some air occupying the space over mercury column. How can the air pressure be correctly determined with this faulty barometer?

Give three properties which have different magnitudes and also have different direction.

What are longitudinal and transverse waves ?

A uniform chain of length L and mass M is lying on a smooth table and one third of its length is hanging vertically down over the edge of the table. If g is acceleration due to gravity, work required to pull the hanging part on to the table is

A person in an elevator accelerating upwards with an acceleration of 2 ms^(2) tosses a coin vertically upwards with a speed of 20ms^(-2) After how much time will the coin fall back into his hand ? (g = 10 ms^(-2)).

Time period of mars to revolve around Sun is 8 times greater than that of Mercury. If distance of Mercury from Sun is 5.79xx10^10 m then that of Mars is approximately …... .

If a body is projected with angle theta to the horizontal, then ·

A ball of mass m , moving with a speed 2v_(0) collides inelastically ( e gt 0) with an identicalball at rest . Show that (a) For head - on collision , both the balls move forward . (b) For a general collision , the angle between the two velocities of scattered balls is less than 90^(@)

A child sits stationary at one end of a long trolley moving uniformly with a speed V on a smooth horizontal floor. If the child gets up and runs about on the trolley in any manner, what is the speed of the CM of the (trolley + child) system?

Check the correctness of the equation 1/2 mv^(2) = mgh using dimensional analysis method.

Which of the followingquantities remain constant in a planetory motion (consider elliptical orbits) as seen from the sun ?

………. vecF .vecs scalar quantity

A particle executes simple harmonic motion between X=-A and X=+A. The time taken for it to go from 0 to A/2is T_1 and to go from A/2 is T, then:

barF=abari+3barj+6 bark and bar r=2bari-6 barj-12 bark. The value of a. for which the angular momentum is conserved is

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