50278 + Interview Questions in Physics

1.	A,B and C are three objects each moving with constant velocity. A′s speed is 10 m/s in a direction PQ. The velocity of B relative to A is 6 m/s at an angle of cos−1(15/24) to PQ. The velocity of C relative to B is 12 m/s in the direction QP, then find the magnitude of velocity of C.
Answer» $A, B$ and $C$ are three objects each moving with constant velocity. $A^{'}$ s speed is $10 m/s$ in a direction $P Q$ . The velocity of $B$ relative to $A$ is $6 m/s$ at an angle of ${cos}^{- 1} (15 / 24)$ to $P Q$ . The velocity of $C$ relative to $B$ is $12 m/s$ in the direction $Q P$ , then find the magnitude of velocity of $C$ .

Discussion

2.	38. Two balls each of mass 0.05 kg are moving in opposite direction along the same straight line with the same speed of 6m/s . If they collide and rebound with the same speed what is the impulse imparted to each ball by the other !
Answer» 38. Two balls each of mass 0.05 kg are moving in opposite direction along the same straight line with the same speed of 6m/s . If they collide and rebound with the same speed what is the impulse imparted to each ball by the other !

Discussion

3.	When a conducting soap bubble is negatively charged then what happens to its size ?
Answer» When a conducting soap bubble is negatively charged then what happens to its size ?

Discussion

4.	In a calorimeter (water equivalent=40 g) are 200 g of waterand 50 g of ice all at 0°C. Into this is poured 30 g of water at90°C. What will be the final condition of the system?
Answer» In a calorimeter (water equivalent=40 g) are 200 g of water and 50 g of ice all at 0°C. Into this is poured 30 g of water at 90°C. What will be the final condition of the system?

Discussion

5.	How to find the 6th CN and 3rd CN for a atom in bcc, fcc
Answer» How to find the 6th CN and 3rd CN for a atom in bcc, fcc

Discussion

6.	When a block of mass 2 kg is suspended by a long wire of length 1 m, the length of wire becomes 1.02 m. The elastic potential energy stored in wire is(Take g=10 m/s2)
Answer» When a block of mass $2 kg$ is suspended by a long wire of length $1 m$ , the length of wire becomes $1.02 m$ . The elastic potential energy stored in wire is (Take $g = 10 m / s^{2}$ )

Discussion

7.	Two masses m1 and m2 connected by a light spring of natural length lo is compressed completely and tied by a string. This system while moving with a velocity v alon8g +X-axis pass through the origin at t=0. At this position the string snaps. Position of mass m1 at time t is given by the equation x1(t) =Vot - A(1 - cosω t). Calculate(a) position of the particle m2 as a function of time.(b) lo in terms of A.
Answer» Two masses m1 and m2 connected by a light spring of natural length lo is compressed completely and tied by a string. This system while moving with a velocity v alon8g +X-axis pass through the origin at t=0. At this position the string snaps. Position of mass m1 at time t is given by the equation x1(t) =Vot - A(1 - cosω t). Calculate(a) position of the particle m2 as a function of time.(b) lo in terms of A.

Discussion

8.	A series and RC current is in parallel with series of RL current. Find the value of i at t = 2s.
Answer» A series and RC current is in parallel with series of RL current. Find the value of i at t = 2s.

Discussion

9.	a 30 v ,90w lamp is to be operated on a 120 v dc lines.for proper glow,how much resistance should be connected in series with the lamp?
Answer» a 30 v ,90w lamp is to be operated on a 120 v dc lines.for proper glow,how much resistance should be connected in series with the lamp?

Discussion

10.	why does an ammeter has zero resis†an ce
Answer» why does an ammeter has zero resis†an ce

Discussion

11.	If the velocity of car is increased by 20% then the minimum distance in which it can be stopped increase
Answer» If the velocity of car is increased by 20% then the minimum distance in which it can be stopped increase

Discussion

12.	1g H2 gas expands at STP to occupy double of its original volume the work done during process is
Answer» 1g H2 gas expands at STP to occupy double of its original volume the work done during process is

Discussion

13.	28. A solid floats in water with 3/4 of its volume below the surface of water. Calculate the density of the solid.
Answer» 28. A solid floats in water with 3/4 of its volume below the surface of water. Calculate the density of the solid.

Discussion

14.	A constant retarding force of 50 N is applied to a body of mass 20 kg moving initially with a speed of 15 m s-1. How long does the body take to stop ?
Answer» A constant retarding force of 50 N is applied to a body of mass 20 kg moving initially with a speed of 15 m s-1. How long does the body take to stop ?

Discussion

15.	SI unit of latent heat is
Answer» SI unit of latent heat is

Discussion

16.	139.If at t = 0, a travelling wave pulse on a string is described by the function . What will be the wave function representing the pulse at time t, if the pulse is propagating along positive x-axis with speed 4 m/s?
Answer» 139.If at t = 0, a travelling wave pulse on a string is described by the function . What will be the wave function representing the pulse at time t, if the pulse is propagating along positive x-axis with speed 4 m/s?

Discussion

17.	A block is projected along a rough horizontal surface with a velocity of 5 m/s. If the block comes to rest after travelling a distance of 4 m, then the coefficient of kinetic friction is (Take g=10 m/s2)
Answer» A block is projected along a rough horizontal surface with a velocity of $5 m/s$ . If the block comes to rest after travelling a distance of $4 m$ , then the coefficient of kinetic friction is $(Take g = 10 {m/s}^{2})$

Discussion

18.	A vector →a=x^i+^j+z^k, (x,z∈R) lies in the plane of vectors, →b=^j+^k and →c=^i+^k. If →a bisects the angle between →b and →c, then which of the following statement(s) can be true ?
Answer» A vector $\to a = x^i +^j + z^k, (x, z \in R)$ lies in the plane of vectors, $\to b =^j +^k$ and $\to c =^i +^k .$ If $\to a$ bisects the angle between $\to b$ and $\to c,$ then which of the following statement(s) can be true ?

Discussion

19.	67. Water is flowing through a horizontal pipe of non uniform cross section.The speed of water is 30cm/sec at a place where pressure is 10cm .Calculate the speed of water at the other place where the pressure is half of that at the first place
Answer» 67. Water is flowing through a horizontal pipe of non uniform cross section.The speed of water is 30cm/sec at a place where pressure is 10cm .Calculate the speed of water at the other place where the pressure is half of that at the first place

Discussion

20.	why sodium and lithium have negative electron gainenthalpy?
Answer» why sodium and lithium have negative electron gainenthalpy?

Discussion

21.	A car which has an initial velocity of 4 m/s accelerates at the rate of 2 m/s2 for 5 s. What will be the distance (in m) that it covers in these 5 s ?
Answer» A car which has an initial velocity of $4 m/s$ accelerates at the rate of $2 {m/s}^{2}$ for $5 s$ . What will be the distance (in $m$ ) that it covers in these $5 s$ ?

Discussion

22.	A freshly prepared sample of a radioisotope of half-life 1386 s has activity 103 disintegration per second. Given that ln2=0.693, the fraction of the initial number of nuclei (expressed in the nearest integer percentage) that will decay in the first 80 s after preparation of the sample is ____.
Answer» A freshly prepared sample of a radioisotope of half-life $1386 s$ has activity $10^{3}$ disintegration per second. Given that $ln 2 = 0.693$ , the fraction of the initial number of nuclei (expressed in the nearest integer percentage) that will decay in the first $80 s$ after preparation of the sample is ____.

Discussion

23.	A metal plate (Wnode = 2.5eV) is subjected to a photon having energy 4eV the stopping potential will be
Answer» A metal plate (Wnode = 2.5eV) is subjected to a photon having energy 4eV the stopping potential will be

Discussion

24.	A particle moves with constant acceleration. If v1, v2 and v3 are the three average velocities in three successive intervals t1, t2 and t3 of time. Then prove that v1-v2/v2- v3 = t1 + t2/t2+ t3
Answer» A particle moves with constant acceleration. If v1, v2 and v3 are the three average velocities in three successive intervals t1, t2 and t3 of time. Then prove that v1-v2/v2- v3 = t1 + t2/t2+ t3

Discussion

25.	A man is observing, from the top of a tower, a boat speeding towards the tower from a certain point A, with uniform speed. At that point, angle of depression of the boat with the man’s eye is 30∘ (Ignore man’s height). After sailing for 20 seconds, towards the base of the tower (which is at the level of water), the boat has reached a point B, where the angle of depression is 45∘. Then the time taken (in seconds) by the boat from B to reach the base of the tower is :
Answer» A man is observing, from the top of a tower, a boat speeding towards the tower from a certain point $A,$ with uniform speed. At that point, angle of depression of the boat with the man’s eye is $30^{\circ}$ $($ Ignore man’s height $)$ . After sailing for $20$ seconds, towards the base of the tower $($ which is at the level of water $)$ , the boat has reached a point $B$ , where the angle of depression is $45^{\circ}$ . Then the time taken $($ in seconds $)$ by the boat from $B$ to reach the base of the tower is :

Discussion

26.	21.When the stretching force of a sonometer wire is increased by 2.5kg the frequency produced by it increases by 50% . Find the original stretching force.
Answer» 21.When the stretching force of a sonometer wire is increased by 2.5kg the frequency produced by it increases by 50% . Find the original stretching force.

Discussion

27.	A capacitor of capacitance 0.5 C is connected to a battery of emf 20 V for a long time and then disconnected. The charged capacitor is then connected across a long solenoid having 1000 turns per metre in its closely packed windings on its core. After connection, it is found that the voltage across the capacitor drops to 8 V in a time interval of 2 s. In this period, what is the average magnetic induction at the center of the solenoid.
Answer» A capacitor of capacitance $0.5 C$ is connected to a battery of emf $20 V$ for a long time and then disconnected. The charged capacitor is then connected across a long solenoid having $1000$ turns per $metre$ in its closely packed windings on its core. After connection, it is found that the voltage across the capacitor drops to $8 V$ in a time interval of $2 s$ . In this period, what is the average magnetic induction at the center of the solenoid.

Discussion

28.	Consider the circuit shown in the figure below.The switch in the circuit is initially closed for a long time, at t = 0 it is opened. Then which of the following statement is true.(Assume forward drop of a zener diode = 0.7 V).
Answer» Consider the circuit shown in the figure below. The switch in the circuit is initially closed for a long time, at t = 0 it is opened. Then which of the following statement is true. (Assume forward drop of a zener diode = 0.7 V).

Discussion

29.	A particle is projected with velocity V not greater than 10 metre per second find the distance travelled in last one second before velocity becomes zero
Answer» A particle is projected with velocity V not greater than 10 metre per second find the distance travelled in last one second before velocity becomes zero

Discussion

30.	An electric bulb is designed to consume 100 W at 200 V. It is connected to a 300 V and ω=100 r/s A.C. source. For what value of inductance (in henry) of the coil bulb, will we get correct voltage?
Answer» An electric bulb is designed to consume 100 W at 200 V. It is connected to a 300 V and $ω = 100 r / s$ A.C. source. For what value of inductance (in henry) of the coil bulb, will we get correct voltage?

Discussion

31.	Two concentric conducting spheres are of radii r1 and r2 . The outer sphere is a given a charge Q . What will be the charge q on the inner surface (inner surface is grounded)?
Answer» Two concentric conducting spheres are of radii r1 and r2 . The outer sphere is a given a charge Q . What will be the charge q on the inner surface (inner surface is grounded)?

Discussion

32.	33.When an an electron in Hydrogen atom jumps from the 3rd excited state to the ground state, how would the de Broglie wavelength have associated with the electron change?
Answer» 33.When an an electron in Hydrogen atom jumps from the 3rd excited state to the ground state, how would the de Broglie wavelength have associated with the electron change?

Discussion

33.	56. The length of second pendulum at the surface of earth is 1 m.determine the length of second pendulum at the surface of moon.
Answer» 56. The length of second pendulum at the surface of earth is 1 m.determine the length of second pendulum at the surface of moon.

Discussion

34.	The electrons, identified by quantum numbers n and l,(i) n=4,l=1, (ii) n=4,l=0, (iii) n=3,l=2, (iv) n=3,l=1 can be placed in order of increasing energy, from the lowest to highest, as:
Answer» The electrons, identified by quantum numbers $n$ and $l$ , $(i) n = 4, l = 1, (i i) n = 4, l = 0, (i i i) n = 3, l = 2, (i v) n = 3, l = 1$ can be placed in order of increasing energy, from the lowest to highest, as:

Discussion

35.	A cell of emf ε is connected across thick spherical shell of inner radius R1 and outer radius R2 as shown in figure. If resitivity of sphere is ρ, current through the cell is:
Answer» A cell of emf $ε$ is connected across thick spherical shell of inner radius $R_{1}$ and outer radius $R_{2}$ as shown in figure. If resitivity of sphere is $ρ$ , current through the cell is:

Discussion

36.	A uniform disc of mass m and radius R=8023π2 is pivoted smoothly at point P. If another uniform ring of mass m and radius R is welded at the lowest point of the disc, the time period (in seconds) of the SHM of the system is
Answer» A uniform disc of mass $m$ and radius $R = \frac{80}{23 π^{2}}$ is pivoted smoothly at point $P$ . If another uniform ring of mass $m$ and radius $R$ is welded at the lowest point of the disc, the time period (in seconds) of the SHM of the system is

Discussion

37.	A uniform rod of length l and mass m is free to rotate in a vertical plane about A. The rod initially in horizontal position is released. The initial angular acceleration of the rod is (Moment of inertia of rod about A is ml23)
Answer» A uniform rod of length $l$ and mass $m$ is free to rotate in a vertical plane about $A$ . The rod initially in horizontal position is released. The initial angular acceleration of the rod is (Moment of inertia of rod about $A$ is $\frac{m l^{2}}{3}$ )

Discussion

38.	The time period of a pendulum in the elevator that is accelerating at g upward
Answer» The time period of a pendulum in the elevator that is accelerating at g upward

Discussion

39.	How accleration in uniform circular motion is towards the centre ?
Answer» How accleration in uniform circular motion is towards the centre ?

Discussion

40.	if mass of the earth decreases by 25% and its radius increases by 50%, then the accelaration due to gravity at its surface decreases by nearly?
Answer» if mass of the earth decreases by 25% and its radius increases by 50%, then the accelaration due to gravity at its surface decreases by nearly?

Discussion

41.	A simple pendulum has a time period T1 when on the earth's surface and T2 when taken to a height R above the earth's surface, where R is the radius of the earth. The value of T2T1 is :
Answer» A simple pendulum has a time period $T_{1}$ when on the earth's surface and $T_{2}$ when taken to a height R above the earth's surface, where R is the radius of the earth. The value of $\frac{T_{2}}{T_{1}}$ is :

Discussion

42.	The magnetic flux through a coil having 100 turns decreases from 5 milli weber to zero in 5 second.Calculate the e.m.f. induced in the coil.
Answer» The magnetic flux through a coil having 100 turns decreases from 5 milli weber to zero in 5 second.Calculate the e.m.f. induced in the coil.

Discussion

43.	A man on a rectilinearly moving cart, facing the direction of motion, throws a ball straight up wrt himself.
Answer» A man on a rectilinearly moving cart, facing the direction of motion, throws a ball straight up wrt himself.

Discussion

44.	A rod AB of mass M and length 4L rests on a smooth horizontal plane. A small particle P moving with a velocity V strikes the rod elastically in a direction normal to the length, at a point distant L from the centre C of the rod. Immediately after the collision, if P comes to rest, then its mass should be
Answer» A rod AB of mass M and length 4L rests on a smooth horizontal plane. A small particle P moving with a velocity V strikes the rod elastically in a direction normal to the length, at a point distant L from the centre C of the rod. Immediately after the collision, if P comes to rest, then its mass should be

Discussion

45.	how newtons law can be used to find specific heat of liquids in laboratory ?
Answer» how newtons law can be used to find specific heat of liquids in laboratory ?

Discussion

46.	maximum height reached by projectile is 4m the horizontal range is 12m velocity of projection is
Answer» maximum height reached by projectile is 4m the horizontal range is 12m velocity of projection is

Discussion

47.	A cylindrical drum, pushed along by a board rolls forward on the ground. There is on slipping at any contact. Find the distance moved by the man who is pushing the board, when axis of the cylinder covers a distance L.
Answer» A cylindrical drum, pushed along by a board rolls forward on the ground. There is on slipping at any contact. Find the distance moved by the man who is pushing the board, when axis of the cylinder covers a distance L.

47.

A cylindrical drum, pushed along by a board rolls forward on the ground. There is on slipping at any contact. Find the distance moved by the man who is pushing the board, when axis of the cylinder covers a distance L.

Answer»

A cylindrical drum, pushed along by a board rolls forward on the ground. There is on slipping at any contact. Find the distance moved by the man who is pushing the board, when axis of the cylinder covers a distance L.

Discussion

48.	A particle of mass m is moving in circular path under action of central force whose potential is V=−kr5, here r is distance from center, then kinetic energy of particle is proportional to
Answer» A particle of mass $m$ is moving in circular path under action of central force whose potential is $V = - k r^{5}$ , here $r$ is distance from center, then kinetic energy of particle is proportional to

Discussion

49.	An electric current is passed through a circuit containing two wires of the same material connected in parallel. If the lengths and radii of the wires are in the ratio of 4/3 and 2/3 respectively, then the ratio of the currents passing through the wires will be -
Answer» An electric current is passed through a circuit containing two wires of the same material connected in parallel. If the lengths and radii of the wires are in the ratio of $4 / 3$ and $2 / 3$ respectively, then the ratio of the currents passing through the wires will be -

Discussion

50.	A constant force acting on a body of mass 3.0 kg changes its speed from 2.0 m s–1 to 3.5 m s–1 in 25 s. The direction of the motion of the body remains unchanged. What is the magnitude and direction of the force?
Answer» A constant force acting on a body of mass 3.0 kg changes its speed from 2.0 m s^–1 to 3.5 m s^–1 in 25 s. The direction of the motion of the body remains unchanged. What is the magnitude and direction of the force?

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

A,B and C are three objects each moving with constant velocity. A′s speed is 10 m/s in a direction PQ. The velocity of B relative to A is 6 m/s at an angle of cos−1(15/24) to PQ. The velocity of C relative to B is 12 m/s in the direction QP, then find the magnitude of velocity of C.

38. Two balls each of mass 0.05 kg are moving in opposite direction along the same straight line with the same speed of 6m/s . If they collide and rebound with the same speed what is the impulse imparted to each ball by the other !

When a conducting soap bubble is negatively charged then what happens to its size ?

In a calorimeter (water equivalent=40 g) are 200 g of waterand 50 g of ice all at 0°C. Into this is poured 30 g of water at90°C. What will be the final condition of the system?

How to find the 6th CN and 3rd CN for a atom in bcc, fcc

When a block of mass 2 kg is suspended by a long wire of length 1 m, the length of wire becomes 1.02 m. The elastic potential energy stored in wire is(Take g=10 m/s2)

A series and RC current is in parallel with series of RL current. Find the value of i at t = 2s.

a 30 v ,90w lamp is to be operated on a 120 v dc lines.for proper glow,how much resistance should be connected in series with the lamp?

why does an ammeter has zero resis†an ce

If the velocity of car is increased by 20% then the minimum distance in which it can be stopped increase

1g H2 gas expands at STP to occupy double of its original volume the work done during process is

28. A solid floats in water with 3/4 of its volume below the surface of water. Calculate the density of the solid.

A constant retarding force of 50 N is applied to a body of mass 20 kg moving initially with a speed of 15 m s-1. How long does the body take to stop ?

SI unit of latent heat is

139.If at t = 0, a travelling wave pulse on a string is described by the function . What will be the wave function representing the pulse at time t, if the pulse is propagating along positive x-axis with speed 4 m/s?

A block is projected along a rough horizontal surface with a velocity of 5 m/s. If the block comes to rest after travelling a distance of 4 m, then the coefficient of kinetic friction is (Take g=10 m/s2)

A vector →a=x^i+^j+z^k, (x,z∈R) lies in the plane of vectors, →b=^j+^k and →c=^i+^k. If →a bisects the angle between →b and →c, then which of the following statement(s) can be true ?

67. Water is flowing through a horizontal pipe of non uniform cross section.The speed of water is 30cm/sec at a place where pressure is 10cm .Calculate the speed of water at the other place where the pressure is half of that at the first place

why sodium and lithium have negative electron gainenthalpy?

A car which has an initial velocity of 4 m/s accelerates at the rate of 2 m/s2 for 5 s. What will be the distance (in m) that it covers in these 5 s ?

A freshly prepared sample of a radioisotope of half-life 1386 s has activity 103 disintegration per second. Given that ln2=0.693, the fraction of the initial number of nuclei (expressed in the nearest integer percentage) that will decay in the first 80 s after preparation of the sample is ____.

A metal plate (Wnode = 2.5eV) is subjected to a photon having energy 4eV the stopping potential will be

A particle moves with constant acceleration. If v1, v2 and v3 are the three average velocities in three successive intervals t1, t2 and t3 of time. Then prove that v1-v2/v2- v3 = t1 + t2/t2+ t3

21.When the stretching force of a sonometer wire is increased by 2.5kg the frequency produced by it increases by 50% . Find the original stretching force.

Consider the circuit shown in the figure below.The switch in the circuit is initially closed for a long time, at t = 0 it is opened. Then which of the following statement is true.(Assume forward drop of a zener diode = 0.7 V).

A particle is projected with velocity V not greater than 10 metre per second find the distance travelled in last one second before velocity becomes zero

An electric bulb is designed to consume 100 W at 200 V. It is connected to a 300 V and ω=100 r/s A.C. source. For what value of inductance (in henry) of the coil bulb, will we get correct voltage?

Two concentric conducting spheres are of radii r1 and r2 . The outer sphere is a given a charge Q . What will be the charge q on the inner surface (inner surface is grounded)?

33.When an an electron in Hydrogen atom jumps from the 3rd excited state to the ground state, how would the de Broglie wavelength have associated with the electron change?

56. The length of second pendulum at the surface of earth is 1 m.determine the length of second pendulum at the surface of moon.

The electrons, identified by quantum numbers n and l,(i) n=4,l=1, (ii) n=4,l=0, (iii) n=3,l=2, (iv) n=3,l=1 can be placed in order of increasing energy, from the lowest to highest, as:

A cell of emf ε is connected across thick spherical shell of inner radius R1 and outer radius R2 as shown in figure. If resitivity of sphere is ρ, current through the cell is:

A uniform disc of mass m and radius R=8023π2 is pivoted smoothly at point P. If another uniform ring of mass m and radius R is welded at the lowest point of the disc, the time period (in seconds) of the SHM of the system is

A uniform rod of length l and mass m is free to rotate in a vertical plane about A. The rod initially in horizontal position is released. The initial angular acceleration of the rod is (Moment of inertia of rod about A is ml23)

The time period of a pendulum in the elevator that is accelerating at g upward

How accleration in uniform circular motion is towards the centre ?

if mass of the earth decreases by 25% and its radius increases by 50%, then the accelaration due to gravity at its surface decreases by nearly?

A simple pendulum has a time period T1 when on the earth's surface and T2 when taken to a height R above the earth's surface, where R is the radius of the earth. The value of T2T1 is :

The magnetic flux through a coil having 100 turns decreases from 5 milli weber to zero in 5 second.Calculate the e.m.f. induced in the coil.

A man on a rectilinearly moving cart, facing the direction of motion, throws a ball straight up wrt himself.

how newtons law can be used to find specific heat of liquids in laboratory ?

maximum height reached by projectile is 4m the horizontal range is 12m velocity of projection is

A cylindrical drum, pushed along by a board rolls forward on the ground. There is on slipping at any contact. Find the distance moved by the man who is pushing the board, when axis of the cylinder covers a distance L.

A particle of mass m is moving in circular path under action of central force whose potential is V=−kr5, here r is distance from center, then kinetic energy of particle is proportional to

An electric current is passed through a circuit containing two wires of the same material connected in parallel. If the lengths and radii of the wires are in the ratio of 4/3 and 2/3 respectively, then the ratio of the currents passing through the wires will be -

A constant force acting on a body of mass 3.0 kg changes its speed from 2.0 m s–1 to 3.5 m s–1 in 25 s. The direction of the motion of the body remains unchanged. What is the magnitude and direction of the force?