50278 + Interview Questions in Physics

1.	The block of mass m1 shown in figure (12-E2) is fastened to the spring and the block of mass m2 is placed against it. (a) Find the compression of the spring in the equilibrium position. (b) The blocks are pushed a further distance (2/k) (m1+m2)g sin θ against the spring and released. Find the position where the two blocks separate. (c) What is the common speed of blocks at the time of separation ?
Answer» The block of mass $m_{1}$ shown in figure (12-E2) is fastened to the spring and the block of mass $m_{2}$ is placed against it. (a) Find the compression of the spring in the equilibrium position. (b) The blocks are pushed a further distance $(2 / k) (m_{1} + m_{2}) g s i n θ$ against the spring and released. Find the position where the two blocks separate. (c) What is the common speed of blocks at the time of separation ?

1.

The block of mass m1 shown in figure (12-E2) is fastened to the spring and the block of mass m2 is placed against it. (a) Find the compression of the spring in the equilibrium position. (b) The blocks are pushed a further distance (2/k) (m1+m2)g sin θ against the spring and released. Find the position where the two blocks separate. (c) What is the common speed of blocks at the time of separation ?

Answer»

The block of mass $m_{1}$ shown in figure (12-E2) is fastened to the spring and the block of mass $m_{2}$ is placed against it. (a) Find the compression of the spring in the equilibrium position. (b) The blocks are pushed a further distance $(2 / k) (m_{1} + m_{2}) g s i n θ$ against the spring and released. Find the position where the two blocks separate. (c) What is the common speed of blocks at the time of separation ?

2.	The unit vector which, is perpendicular to the vectors →A=^i−2^j+^k and →B=3^i−2^j−^k is
Answer» The unit vector which, is perpendicular to the vectors $\to A =^i - 2^j +^k$ and $\to B = 3^i - 2^j -^k$ is

3.	Sound wave of frequency 600 Hz fall normally on a perfect reflecting wall. The minimum distance from the wall at which particles of the medium will have maximum displacement during its vibrations is [speed of sound =300 m/s]
Answer» Sound wave of frequency $600 Hz$ fall normally on a perfect reflecting wall. The minimum distance from the wall at which particles of the medium will have maximum displacement during its vibrations is [speed of sound $= 300 m/s$ ]

5.	A thin tube of uniform cross section is sealed at both ends. It lies horizontally, the middle 5 cm containing mercury and the parts on its two sides containing air at the same pressure P. When the tube is held at an angle of 60∘ with the vertical, the length of the air column above and below the mercury pellet are 46cm and 44.5cm respectively. Calculate the pressure P in centimeters of mercury. The temperature of the system is kept at 30∘C.
Answer» A thin tube of uniform cross section is sealed at both ends. It lies horizontally, the middle 5 cm containing mercury and the parts on its two sides containing air at the same pressure P. When the tube is held at an angle of $60^{\circ}$ with the vertical, the length of the air column above and below the mercury pellet are 46cm and 44.5cm respectively. Calculate the pressure P in centimeters of mercury. The temperature of the system is kept at $30^{\circ} C$ .

6.	A barometer tube reads 75 cm of Hg. If the tube is gradually inclined at an angle of 30∘ with the horizontal, keeping the open end in the mercury container, find the length of the mercury column in the barometer tube.
Answer» A barometer tube reads $75 cm$ of $H g$ . If the tube is gradually inclined at an angle of $30^{\circ}$ with the horizontal, keeping the open end in the mercury container, find the length of the mercury column in the barometer tube.

7.	Classify the given measure as scalar and vectors: (i) 2 m north-west
Answer» Classify the given measure as scalar and vectors: (i) 2 m north-west

8.	The excess pressure inside a spherical drop of water is four times that of another water drop. Then the mass ratio of the two drops is
Answer» The excess pressure inside a spherical drop of water is four times that of another water drop. Then the mass ratio of the two drops is

9.	A body starts from rest with acceleration 2 m/s2 till it attains the maximum velocity, then retards to rest with 3 m/s2. If total time taken is 10 seconds then maximum speed attained is
Answer» A body starts from rest with acceleration $2 {m/s}^{2}$ till it attains the maximum velocity, then retards to rest with $3 {m/s}^{2}$ . If total time taken is $10$ seconds then maximum speed attained is

10.	For a plane progressive wave represented by, y=5sin(100πt−0.4πx), what is the wave velocity (in m/s)?
Answer» For a plane progressive wave represented by, $y = 5 sin (100 π t - 0.4 π x)$ , what is the wave velocity (in $m/s$ )?

11.	An α−particle experiences the following force due to a nucleus (k>0) →F=kr2ifr>R=−KR3→rifr<R Suppose the particle starts from r=∞ with a kinetic energy just enough to reach r = R. Its kinetic energy at r=R2 will be
Answer» An $α -$ particle experiences the following force due to a nucleus $(k > 0)$ $\begin{matrix} \to F = \frac{k}{r^{2}} & i f & r > R = \frac{- K}{R^{3}} \to r & i f & r < R \end{matrix}$ Suppose the particle starts from $r = \infty$ with a kinetic energy just enough to reach r = R. Its kinetic energy at $r = \frac{R}{2}$ will be

12.	When the load on a wire is slowly increased from 3 to 5 kg wt, the elongation increases from 0.61 to 1.02 mm. The work done during the extension of wire is
Answer» When the load on a wire is slowly increased from 3 to 5 kg wt, the elongation increases from 0.61 to 1.02 mm. The work done during the extension of wire is

13.	The value of acceleration due to gravity is 9.8 ms−2. Its value in km min−2 will be
Answer» The value of acceleration due to gravity is 9.8 $m s^{- 2}$ . Its value in km $m i n^{- 2}$ will be

14.	The moments of inertia of a non-uniform circular disc (of mass M and radius R) about four mutually perpendicular tangents AB,BC CD, DA are I1,I2,I3 and I4 respectively (the square ABCD circumscribes the circle.) The distance of the center of mass of the disc from its geometrical center is given by.
Answer» The moments of inertia of a non-uniform circular disc (of mass M and radius R) about four mutually perpendicular tangents AB,BC CD, DA are $I_{1}, I_{2}, I_{3} a n d I_{4}$ respectively (the square ABCD circumscribes the circle.) The distance of the center of mass of the disc from its geometrical center is given by.

15.	A plano convex lens fits exactly into a plano concave lens. Their plane surface are parallel to each other. If the lenses are made of different materials of refractive indices μ1 and μ2 and R is the radius of curvature of the curved surface of the lenses, then focal length of the combination is
Answer» A plano convex lens fits exactly into a plano concave lens. Their plane surface are parallel to each other. If the lenses are made of different materials of refractive indices $μ_{1}$ and $μ_{2}$ and R is the radius of curvature of the curved surface of the lenses, then focal length of the combination is

16.	A source of sound producing sound of frequency f is at rest. An observer starts moving toward it at t=0 with a constant small acceleration. Which of the following graph best represents the variation of observed frequency f′ recorded by the observer with time t?
Answer» A source of sound producing sound of frequency $f$ is at rest. An observer starts moving toward it at $t = 0$ with a constant small acceleration. Which of the following graph best represents the variation of observed frequency $f^{'}$ recorded by the observer with time $t$ ?

17.	A tuning fork A when sounded with a tuning fork B of frequency 480 Hz produces 5 beats per second. When the prongs of A are loaded with wax, it gives 3 beats per second. The original frequency of the tuning fork A is:
Answer» A tuning fork $A$ when sounded with a tuning fork $B$ of frequency $480 Hz$ produces $5$ beats per second. When the prongs of $A$ are loaded with wax, it gives $3$ beats per second. The original frequency of the tuning fork $A$ is:

18.	A 5 g piece of ice at −20∘C is put into 10 g of water at 30∘C. Assuming that heat is exchanged only between the ice and the water, find the final temperature of the mixture. Specific heat capacity of ice = 2100 J kg−1∘C−1, specific heat capacity of water = 4200 J kg−1∘C−1 and latent heat of fusion of ice = 3.36 × 105 J kg−1.
Answer» A 5 g piece of ice at $- 20^{\circ} C$ is put into 10 g of water at $30^{\circ} C$ . Assuming that heat is exchanged only between the ice and the water, find the final temperature of the mixture. Specific heat capacity of ice = $2100 J k g^{- 1}$ $^{\circ} C^{- 1}$ , specific heat capacity of water = $4200 J k g^{- 1}$ $^{\circ} C^{- 1}$ and latent heat of fusion of ice = $3.36 \times 10^{5} J k g^{- 1}$ .

19.	If the length of a simple pendulum is recorded as (90.0±0.02) cm and period as (1.9±0.02) s, the percentage of error in the measurement of acceleration due to gravity is
Answer» If the length of a simple pendulum is recorded as $(90.0 \pm 0.02) cm$ and period as $(1.9 \pm 0.02) s$ , the percentage of error in the measurement of acceleration due to gravity is

20.	A lake is covered with ice and the atmospheric temperature above the ice is −10∘C. Find the rate of formation of ice (in cm/hr) when its thickness is 5 cm. [Thermal conductivity of ice =0.005 cgs units, density of ice =0.9 g/cc and latent heat of fusion of ice =80 cal/g].
Answer» A lake is covered with ice and the atmospheric temperature above the ice is $- 10^{\circ} C$ . Find the rate of formation of ice $(in cm/hr)$ when its thickness is $5 cm$ . [Thermal conductivity of ice $= 0.005 cgs$ units, density of ice $= 0.9 g/cc$ and latent heat of fusion of ice $= 80 cal/g$ ].

21.	An electron in ground state of hydrogen has an angular momentum L1 and an electron in the first excited state of Lithium has an angular momentum L2. Then
Answer» An electron in ground state of hydrogen has an angular momentum $L_{1}$ and an electron in the first excited state of Lithium has an angular momentum $L_{2}$ . Then

23.	The work function of a metal is hv0. Light of frequency v falls on this metal. The photoelectric effect will take place only if
Answer» The work function of a metal is $h v_{0}$ . Light of frequency v falls on this metal. The photoelectric effect will take place only if

24.	The speed-time graph of a particle moving along a fixed direction is shown in Fig. 3.28. Obtain the distance traversed by the particle between (a) t = 0 s to 10 s, (b) t = 2 s to 6 s. What is the average speed of the particle over the intervals in (a) and (b)?
Answer» The speed-time graph of a particle moving along a fixed direction is shown in Fig. 3.28. Obtain the distance traversed by the particle between (a) t = 0 s to 10 s, (b) t = 2 s to 6 s. What is the average speed of the particle over the intervals in (a) and (b)?

25.	Two travelling waves y1=Asin[k(x+ct)] and y2=Asin[k(x−ct)] are superposed on a string. The distance between adjacent nodes is
Answer» Two travelling waves $y_{1} = A s i n [k (x + c t)]$ and $y_{2} = A s i n [k (x - c t)]$ are superposed on a string. The distance between adjacent nodes is

26.	A body is projected at such an angle that the horizontal range is three times the greatest height. The angle of projection is
Answer» A body is projected at such an angle that the horizontal range is three times the greatest height. The angle of projection is

27.	If the force constant of a wire is K, the work done in increasing the length of the wire by l is
Answer» If the force constant of a wire is K, the work done in increasing the length of the wire by l is

Explore topic-wise InterviewSolutions in Current Affairs.

The unit vector which, is perpendicular to the vectors →A=^i−2^j+^k and →B=3^i−2^j−^k is

Sound wave of frequency 600 Hz fall normally on a perfect reflecting wall. The minimum distance from the wall at which particles of the medium will have maximum displacement during its vibrations is [speed of sound =300 m/s]

A point source radiates energy at the rate of 10 Joules per second, or 10 Watts. As shown in the diagram, two spherical shells of radii r1 and r2 (r1 &lt; r2) receive energies E1 and E2 per second, respectively. Which of the following option(s) is/are true?

A barometer tube reads 75 cm of Hg. If the tube is gradually inclined at an angle of 30∘ with the horizontal, keeping the open end in the mercury container, find the length of the mercury column in the barometer tube.

Classify the given measure as scalar and vectors: (i) 2 m north-west

The excess pressure inside a spherical drop of water is four times that of another water drop. Then the mass ratio of the two drops is

A body starts from rest with acceleration 2 m/s2 till it attains the maximum velocity, then retards to rest with 3 m/s2. If total time taken is 10 seconds then maximum speed attained is

For a plane progressive wave represented by, y=5sin(100πt−0.4πx), what is the wave velocity (in m/s)?

An α−particle experiences the following force due to a nucleus (k&gt;0) →F=kr2ifr&gt;R=−KR3→rifr&lt;R Suppose the particle starts from r=∞ with a kinetic energy just enough to reach r = R. Its kinetic energy at r=R2 will be

When the load on a wire is slowly increased from 3 to 5 kg wt, the elongation increases from 0.61 to 1.02 mm. The work done during the extension of wire is

The value of acceleration due to gravity is 9.8 ms−2. Its value in km min−2 will be

The moments of inertia of a non-uniform circular disc (of mass M and radius R) about four mutually perpendicular tangents AB,BC CD, DA are I1,I2,I3 and I4 respectively (the square ABCD circumscribes the circle.) The distance of the center of mass of the disc from its geometrical center is given by.

A plano convex lens fits exactly into a plano concave lens. Their plane surface are parallel to each other. If the lenses are made of different materials of refractive indices μ1 and μ2 and R is the radius of curvature of the curved surface of the lenses, then focal length of the combination is

A source of sound producing sound of frequency f is at rest. An observer starts moving toward it at t=0 with a constant small acceleration. Which of the following graph best represents the variation of observed frequency f′ recorded by the observer with time t?

A tuning fork A when sounded with a tuning fork B of frequency 480 Hz produces 5 beats per second. When the prongs of A are loaded with wax, it gives 3 beats per second. The original frequency of the tuning fork A is:

If the length of a simple pendulum is recorded as (90.0±0.02) cm and period as (1.9±0.02) s, the percentage of error in the measurement of acceleration due to gravity is

A lake is covered with ice and the atmospheric temperature above the ice is −10∘C. Find the rate of formation of ice (in cm/hr) when its thickness is 5 cm. [Thermal conductivity of ice =0.005 cgs units, density of ice =0.9 g/cc and latent heat of fusion of ice =80 cal/g].

An electron in ground state of hydrogen has an angular momentum L1 and an electron in the first excited state of Lithium has an angular momentum L2. Then

Find the potential energy of the gravitational interaction of a mass point m and a thin uniform rod of mass m and length L if they are located along a straight line at a distance 'a' from each other

The work function of a metal is hv0. Light of frequency v falls on this metal. The photoelectric effect will take place only if

The speed-time graph of a particle moving along a fixed direction is shown in Fig. 3.28. Obtain the distance traversed by the particle between (a) t = 0 s to 10 s, (b) t = 2 s to 6 s. What is the average speed of the particle over the intervals in (a) and (b)?

Two travelling waves y1=Asin[k(x+ct)] and y2=Asin[k(x−ct)] are superposed on a string. The distance between adjacent nodes is

A body is projected at such an angle that the horizontal range is three times the greatest height. The angle of projection is

If the force constant of a wire is K, the work done in increasing the length of the wire by l is

the vector representing the body diagonal from the origin is?

(i) Position vector →A (1) 2^i+^j (ii) Postion vector →B (2) 3^i+3^j (iii) Displacement →dAB (3) 5^i+4^j (iv) Position vector of point of intersection of path 1 &amp; path 2 (4) 4^i+3^j

The escape velocity from the earth is about 11kms−1. The escape velocity from a planet having twice the radius and the same mean density as the earth, is

The volume of gas is reduced to half from its original volume. The specific heat will be (a) reduce to half (b) be doubled (c) remain constant (d) increase four times

A gramophone disc rotates with an uniform angular velocity of 6 rad/sec. A coin of mass 2 gm is placed 5 cm from the centre. The centripetal force acting on the coin is

How can one "prove” Newton's first law?

When a U238 nucleus originally at rest decays by emitting an alpha particle having velocity u, the recoil velocity of the residual nucleus is

The slope of velocity-time graph gives:

A block is placed on a rough floor and a horizontal external force F is applied on it. The force of friction f by the floor on the block is measured for different values of F and a graph is plotted between them. (taking f on Y and F on X axis)

In the pulley arrangement shown in figure, pulley P2 is movable. Assuming the coefficient of friction between the block having mass m and the surface is μ, find the maximum value of M for which m is at rest.

If F represents the strength of cohesive force, then what will be the correct order for strength of cohesive force for solid, liquid and gas ?

In a common base amplifier, the phase difference between the input signal voltage and output voltage is

The area under acceleration - time graph represents the ___________

In order to find out the amount you must change the time on your clock, which of this is sufficient?

Find the value of cos(24o)+cos(5o)+cos(175o)+cos(204o)+cos(300o).

The graph between the resistive force F acting on a body and the distance covered by the body is shown in the figure. The mass of the body is 25 kg and initial velocity is 2 m/s. When the distance covered by the body is 5m, its kinetic energy would be

A block of mass M is pulled on a smooth horizontal table by a string making an angle θ with the horizontal as shown in figure. If the acceleration of the block is 'a', find the force applied by the string and by the table on the block.

The random error in arithmetic mean of 100 observations is x, then random error in arithmetic mean of 400 observations would be

The constant γ for oxygen as well as for hydrogen is 1.40. If the speed of sound in oxygen is 470 m s−1, what will be the speed in hydrogen at the same temperature and pressure?

A point source radiates energy at the rate of 10 Joules per second, or 10 Watts. As shown in the diagram, two spherical shells of radii r1 and r2 (r1 < r2) receive energies E1 and E2 per second, respectively. Which of the following option(s) is/are true?

An α−particle experiences the following force due to a nucleus (k>0) →F=kr2ifr>R=−KR3→rifr<R Suppose the particle starts from r=∞ with a kinetic energy just enough to reach r = R. Its kinetic energy at r=R2 will be

(i) Position vector →A (1) 2^i+^j (ii) Postion vector →B (2) 3^i+3^j (iii) Displacement →dAB (3) 5^i+4^j (iv) Position vector of point of intersection of path 1 & path 2 (4) 4^i+3^j

30.	The escape velocity from the earth is about 11kms−1. The escape velocity from a planet having twice the radius and the same mean density as the earth, is
Answer» The escape velocity from the earth is about $11 k m s^{- 1}$ . The escape velocity from a planet having twice the radius and the same mean density as the earth, is

31.	The volume of gas is reduced to half from its original volume. The specific heat will be (a) reduce to half (b) be doubled (c) remain constant (d) increase four times
Answer» The volume of gas is reduced to half from its original volume. The specific heat will be (a) reduce to half (b) be doubled (c) remain constant (d) increase four times

32.	Two metallic spheres S1 and S2 are made of the same material and have got identical surface finish. The mass of S1 is thrice that of S2. Both the spheres are heated to same high temperature and placed in the same room having lower temperature but are thermally insulated from each other. The ratio of the initial rate of cooling of S1 to that S2 is
Answer» Two metallic spheres $S_{1}$ and $S_{2}$ are made of the same material and have got identical surface finish. The mass of $S_{1}$ is thrice that of $S_{2}$ . Both the spheres are heated to same high temperature and placed in the same room having lower temperature but are thermally insulated from each other. The ratio of the initial rate of cooling of $S_{1}$ to that $S_{2}$ is

33.	A gramophone disc rotates with an uniform angular velocity of 6 rad/sec. A coin of mass 2 gm is placed 5 cm from the centre. The centripetal force acting on the coin is
Answer» A gramophone disc rotates with an uniform angular velocity of $6 rad/sec$ . A coin of mass $2 gm$ is placed $5 cm$ from the centre. The centripetal force acting on the coin is

34.	How can one "prove” Newton's first law?
Answer» How can one "prove” Newton's first law?

35.	When a U238 nucleus originally at rest decays by emitting an alpha particle having velocity u, the recoil velocity of the residual nucleus is
Answer» When a $U^{238}$ nucleus originally at rest decays by emitting an alpha particle having velocity $u$ , the recoil velocity of the residual nucleus is

36.	A block of mass m is placed on another block of mass M, which itself is lying on a horizontal surface. The coefficient of friction between the two blocks is μ1 and that between the block of mass M and the horizontal surface is μ2. What maximum horizontal force can be applied to the lower block so that the two blocks move without separation?
Answer» A block of mass $m$ is placed on another block of mass $M$ , which itself is lying on a horizontal surface. The coefficient of friction between the two blocks is $μ_{1}$ and that between the block of mass $M$ and the horizontal surface is $μ_{2}$ . What maximum horizontal force can be applied to the lower block so that the two blocks move without separation?

37.	The slope of velocity-time graph gives:
Answer» The slope of velocity-time graph gives:

38.	A block is placed on a rough floor and a horizontal external force F is applied on it. The force of friction f by the floor on the block is measured for different values of F and a graph is plotted between them. (taking f on Y and F on X axis)
Answer» A block is placed on a rough floor and a horizontal external force F is applied on it. The force of friction f by the floor on the block is measured for different values of F and a graph is plotted between them. (taking f on Y and F on X axis)

39.	In the pulley arrangement shown in figure, pulley P2 is movable. Assuming the coefficient of friction between the block having mass m and the surface is μ, find the maximum value of M for which m is at rest.
Answer» In the pulley arrangement shown in figure, pulley $P_{2}$ is movable. Assuming the coefficient of friction between the block having mass $m$ and the surface is $μ$ , find the maximum value of $M$ for which $m$ is at rest.