50278 + Interview Questions in Physics

1.	Three blocks m1,m2 and m3 of masses 8 kg,3 kg and 1 kg are placed in contact on a smooth surface. Forces F1=140 N and F2=20 N are acting on blocks m1 and m3 respectively as shown. The reaction between blocks m2 and m3 is
Answer» Three blocks $m_{1}, m_{2}$ and $m_{3}$ of masses $8 kg, 3 kg$ and $1 kg$ are placed in contact on a smooth surface. Forces $F_{1} = 140 N$ and $F_{2} = 20 N$ are acting on blocks $m_{1}$ and $m_{3}$ respectively as shown. The reaction between blocks $m_{2}$ and $m_{3}$ is

Discussion

2.	What should be the pressure inside a air bubble of radius 0.1 mm situated 1 m below the water surface? (Take surface tension of water T=7.2×10−2 N/m and g=10 m/s2)
Answer» What should be the pressure inside a air bubble of radius $0.1 mm$ situated $1 m$ below the water surface? (Take surface tension of water $T = 7.2 \times 10^{- 2} N/m$ and $g = 10 {m/s}^{2}$ )

Discussion

3.	Why work done by pseudo force always negative?
Answer» Why work done by pseudo force always negative?

Discussion

4.	The length of a simple pendulum executing simple harmonic motion is increased by 10%. The percentage increase in the time period of the pendulum due to increased length will be:
Answer» The length of a simple pendulum executing simple harmonic motion is increased by $10 %$ . The percentage increase in the time period of the pendulum due to increased length will be:

Discussion

5.	State and prove Newton's law of Cooling.Also show the cooling curve.
Answer» State and prove Newton's law of Cooling.Also show the cooling curve.

Discussion

6.	A body of mass 1 kg travelling due East with 3 m/s turns due North to travel with the same velocity. Find the net force exerted on the body for it to turn if it takes 0.01 sec to turn
Answer» A body of mass 1 $k g$ travelling due East with $3 m / s$ turns due North to travel with the same velocity. Find the net force exerted on the body for it to turn if it takes $0.01$ sec to turn

Discussion

7.	Number of electric lines of force from 0.5 C of positive charge in a dielectric medium of dielectric constant 10 is
Answer» Number of electric lines of force from 0.5 C of positive charge in a dielectric medium of dielectric constant 10 is

Discussion

8.	A 5.0 diopter lens forms a virtual image which is 4 times the object placed perpendicularly on the principal axis of the lens. Find the distance of the object from the lens.
Answer» A 5.0 diopter lens forms a virtual image which is 4 times the object placed perpendicularly on the principal axis of the lens. Find the distance of the object from the lens.

Discussion

9.	Two 120V Light bulbs, one of 25W and other of 200W are connected on series across a 240V line. One bulb burnt instantly. Which one was burnt and why? Explain
Answer» Two 120V Light bulbs, one of 25W and other of 200W are connected on series across a 240V line. One bulb burnt instantly. Which one was burnt and why? Explain

Discussion

10.	The direct conversion of A to B is difficult, hence it is carried out by the following shown path: C ⟶ D ↑A ↓B Given ΔS(A→C) = 50 e.u.,ΔS(C→D) = 30 e.u., ΔS(B→D) = 20 e.u., where e.u. is the entropy unit, then ΔS(A→B) is
Answer» The direct conversion of A to B is difficult, hence it is carried out by the following shown path: $C ⟶ D$ $↑ A ↓ B$ Given $Δ S_{(A \to C)} = 50 e . u ., Δ S_{(C \to D)} = 30 e . u .$ , $Δ S_{(B \to D)} = 20 e . u .$ , where e.u. is the entropy unit, then $Δ S_{(A \to B)}$ is

10.

The direct conversion of A to B is difficult, hence it is carried out by the following shown path: C ⟶ D ↑A ↓B Given ΔS(A→C) = 50 e.u.,ΔS(C→D) = 30 e.u., ΔS(B→D) = 20 e.u., where e.u. is the entropy unit, then ΔS(A→B) is

Answer»

The direct conversion of A to B is difficult, hence it is carried out by the following shown path:

$C ⟶ D$

$↑ A ↓ B$

Given

$Δ S_{(A \to C)} = 50 e . u ., Δ S_{(C \to D)} = 30 e . u .$ ,

$Δ S_{(B \to D)} = 20 e . u .$ , where e.u. is the entropy unit, then $Δ S_{(A \to B)}$ is

Discussion

11.	Why skin effect is shown by AC and not by DC?
Answer» Why skin effect is shown by AC and not by DC?

Discussion

12.	The ratio of the energies of photons of 2000Å to that of 4000Å is
Answer» The ratio of the energies of photons of $2000 Å$ to that of $4000 Å$ is

Discussion

13.	Four like charges each of +q are placed at the corners of a square of side a. The electric field intensity at the centre of square will be:
Answer» Four like charges each of +q are placed at the corners of a square of side a. The electric field intensity at the centre of square will be:

Discussion

14.	A person A pushes a body of 5 kg placed on a rough surface of co-efficient of friction 0.3 by a distance of 4 m in 15 seconds. Another person B pushes the body of 7 kg on same surface by a distance of 3 m in the same time. Who has more energy and power?
Answer» A person A pushes a body of 5 kg placed on a rough surface of co-efficient of friction 0.3 by a distance of 4 m in 15 seconds. Another person B pushes the body of 7 kg on same surface by a distance of 3 m in the same time. Who has more energy and power?

Discussion

15.	In a circus stuntman rides a motorbike in a circular track of radius R in the vertical plane. The minimum speed at highest point of track will be
Answer» In a circus stuntman rides a motorbike in a circular track of radius R in the vertical plane. The minimum speed at highest point of track will be

Discussion

16.	A photoelectric cell is illuminated by a point source of light 1 m away. When the source is shifted to 2 m then
Answer» A photoelectric cell is illuminated by a point source of light 1 m away. When the source is shifted to 2 m then

Discussion

17.	The power of a pump, which can pump 200kg of water to a height of 200m in 10sec is (g=10m/s−2)
Answer» The power of a pump, which can pump 200kg of water to a height of 200m in 10sec is ( $g = 10 m / s^{- 2}$ )

17.

The power of a pump, which can pump 200kg of water to a height of 200m in 10sec is (g=10m/s−2)

Answer»

The power of a pump, which can pump 200kg of water to a height of 200m in 10sec is ( $g = 10 m / s^{- 2}$ )

Discussion

18.	A small metal sphere, carrying a net charge of q1=−2μC, is held in a stationery position by insulating supports. A second small metal sphere, with a net charge of q2=−8μC and mass 1.50 g is projected towards q1. When the two spheres are 0.800m apart, q2 is moving towards q1 with speed 20 ms−1 as shown in the figure. Assume that the two spheres can be treated as point charges. You can ignore the force of gravity. How close does q2 get to q1?
Answer» A small metal sphere, carrying a net charge of $q_{1} = - 2 μ C$ , is held in a stationery position by insulating supports. A second small metal sphere, with a net charge of $q_{2} = - 8 μ C$ and mass $1.50 g$ is projected towards $q_{1}$ . When the two spheres are $0.800 m$ apart, $q_{2}$ is moving towards $q_{1}$ with speed $20 m s^{- 1}$ as shown in the figure. Assume that the two spheres can be treated as point charges. You can ignore the force of gravity. How close does $q_{2}$ get to $q_{1}$ ?

Discussion

19.	Identify the electromagnetic waves whose wavelengths vary as (a) 10−12m<λ<10−8m (b) 10−3m<λ<10−1m Write one use for each.
Answer» Identify the electromagnetic waves whose wavelengths vary as (a) $10^{- 12} m < λ < 10^{- 8} m$ (b) $10^{- 3} m < λ < 10^{- 1} m$ Write one use for each.

Discussion

20.	In a common-emitter amplifier, using output resistance of 5000 ohm and input resistance of 2000 ohm, if the peak value of input signal voltage is 10 mV and β=50, then the power gain is
Answer» In a common-emitter amplifier, using output resistance of $5000 ohm$ and input resistance of $2000 ohm$ , if the peak value of input signal voltage is $10 mV$ and $β = 50$ , then the power gain is

Discussion

21.	Draw a labelled ray diagram of a refracting telescope. Define its magnifying power and write the expression for it. Write two important limitations of a refracting telescope over a reflecting type telescope.
Answer» Draw a labelled ray diagram of a refracting telescope. Define its magnifying power and write the expression for it. Write two important limitations of a refracting telescope over a reflecting type telescope.

Discussion

22.	Spring fitted doors close by themselves when released. You want to keep the door open for a long time, say for an hour. If you put a half kg stone in front of the open door, it does not help. The stone slides with the door and the door gets closed. However, if you sandwich a 20 gm piece of wood in the small gap between the door and the floor, the door stays open. Explain why a much lighter piece of wood is able to keep the door open while the heavy stone fails. Assume coefficient of friction between stone and ground and wood and ground are the same.
Answer» Spring fitted doors close by themselves when released. You want to keep the door open for a long time, say for an hour. If you put a half kg stone in front of the open door, it does not help. The stone slides with the door and the door gets closed. However, if you sandwich a 20 gm piece of wood in the small gap between the door and the floor, the door stays open. Explain why a much lighter piece of wood is able to keep the door open while the heavy stone fails. Assume coefficient of friction between stone and ground and wood and ground are the same.

Discussion

23.	An object is to be seen through a simple microscope of focal length 12 cm. Where should the object be placed so as to produce maximum angular magnification? The least distance for clear vision is 25 cm.
Answer» An object is to be seen through a simple microscope of focal length 12 cm. Where should the object be placed so as to produce maximum angular magnification? The least distance for clear vision is 25 cm.

Discussion

24.	White coherent light (400 nm - 700 nm) is sent through the slits of a young's double slit experiment (figure 17-E3). The separation between the slits is 0.5 mm and the screen is 50 cm away from the slits. There is a hole in the screen at a point 1.0 mm away (aong the width of the fringes) from the central line. (a) Which wavelength (s) will be absent in the light coming from the hole? (b) Which wavelength (s) willl have a strong intensity?
Answer» White coherent light (400 nm - 700 nm) is sent through the slits of a young's double slit experiment (figure 17-E3). The separation between the slits is 0.5 mm and the screen is 50 cm away from the slits. There is a hole in the screen at a point 1.0 mm away (aong the width of the fringes) from the central line. (a) Which wavelength (s) will be absent in the light coming from the hole? (b) Which wavelength (s) willl have a strong intensity?

24.

White coherent light (400 nm - 700 nm) is sent through the slits of a young's double slit experiment (figure 17-E3). The separation between the slits is 0.5 mm and the screen is 50 cm away from the slits. There is a hole in the screen at a point 1.0 mm away (aong the width of the fringes) from the central line. (a) Which wavelength (s) will be absent in the light coming from the hole? (b) Which wavelength (s) willl have a strong intensity?

Answer»

White coherent light (400 nm - 700 nm) is sent through the slits of a young's double slit experiment (figure 17-E3). The separation between the slits is 0.5 mm and the screen is 50 cm away from the slits. There is a hole in the screen at a point 1.0 mm away (aong the width of the fringes) from the central line. (a) Which wavelength (s) will be absent in the light coming from the hole? (b) Which wavelength (s) willl have a strong intensity?

Discussion

25.	A projectile is thrown with a speed of 100 m/s making an angle of 60∘ with the horizontal. Find the minimum time after which its inclination with the horizontal is 45∘.
Answer» A projectile is thrown with a speed of $100 m / s$ making an angle of $60^{\circ}$ with the horizontal. Find the minimum time after which its inclination with the horizontal is $45^{\circ}$ .

Discussion

26.	A particle starts with some initial velocity and covers x1 distance with a1 acceleration and further x2 distance with a2 acceleration. If the final velocity is same as initial velocity then
Answer» A particle starts with some initial velocity and covers $x_{1}$ distance with $a_{1}$ acceleration and further $x_{2}$ distance with $a_{2}$ acceleration. If the final velocity is same as initial velocity then

Discussion

27.	For a gas, the r.m.s. speed at 800 K is
Answer» For a gas, the r.m.s. speed at 800 K is

27.

For a gas, the r.m.s. speed at 800 K is

Answer»

For a gas, the r.m.s. speed at 800 K is

Discussion

28.	Which of the following expressions represent simple harmonic motion [Roorkee 1999]
Answer» Which of the following expressions represent simple harmonic motion [Roorkee 1999]

28.

Which of the following expressions represent simple harmonic motion [Roorkee 1999]

Answer»

Which of the following expressions represent simple harmonic motion

[Roorkee 1999]

Discussion

29.	How much heat energy is gained when 5 kg of water at 20∘C is brought to its boiling point? (Specific heat of water=4.2 kJ kg−1c−1)
Answer» How much heat energy is gained when $5 k g$ of water at $20^{\circ} C$ is brought to its boiling point? $(Specific heat of water = 4.2 k J k g^{- 1} c^{- 1})$

Discussion

30.	One end of a copper rod of uniform cross-section and of length 3.1 m is kept in contact with ice and the other end with water at 100∘ C. At what point along it's length should a temperature of 200∘ C be maintained so that in steady state, the mass of ice melting be equal to that of the steam produced in the same interval of time. Assume that the whole system is insulated from the surroundings. Latent heat of fusion of ice and vaporisation of water are 80 cal/gm and 540 cal/gm respectively
Answer» One end of a copper rod of uniform cross-section and of length 3.1 m is kept in contact with ice and the other end with water at $100^{\circ}$ C. At what point along it's length should a temperature of $200^{\circ}$ C be maintained so that in steady state, the mass of ice melting be equal to that of the steam produced in the same interval of time. Assume that the whole system is insulated from the surroundings. Latent heat of fusion of ice and vaporisation of water are 80 cal/gm and 540 cal/gm respectively

Discussion

31.	Find the charge on each of the capacitors 0.20 ms after the switch S is closed in figure (32-E34).
Answer» Find the charge on each of the capacitors 0.20 ms after the switch S is closed in figure (32-E34).

31.

Find the charge on each of the capacitors 0.20 ms after the switch S is closed in figure (32-E34).

Answer»

Find the charge on each of the capacitors 0.20 ms after the switch S is closed in figure (32-E34).

Discussion

32.	Two bodies of masses m1 and m2 and specific heat capacities s1 and s2 are connected by a rod of length l, cross -sectional area A, thermal conductivity K and negligible heat capacity. The whole system is thermally insulated. At time t = 0, the temperature of thr first body is T1 and the temperature of the second body is T2(T2>T1). Find the temperature difference between the two bodies at time t.
Answer» Two bodies of masses $m_{1}$ and $m_{2}$ and specific heat capacities $s_{1}$ and $s_{2}$ are connected by a rod of length l, cross -sectional area A, thermal conductivity K and negligible heat capacity. The whole system is thermally insulated. At time t = 0, the temperature of thr first body is $T_{1}$ and the temperature of the second body is $T_{2} (T_{2} > T_{1})$ . Find the temperature difference between the two bodies at time t.

Discussion

33.	The rate of radiation of a black body at 0o C is E J/sec. The rate of radiation of this black body at 273o C will be
Answer» The rate of radiation of a black body at $0^{o} C$ is E J/sec. The rate of radiation of this black body at $273^{o} C$ will be

33.

The rate of radiation of a black body at 0o C is E J/sec. The rate of radiation of this black body at 273o C will be

Answer»

The rate of radiation of a black body at $0^{o} C$ is E J/sec. The rate of radiation of this black body at $273^{o} C$ will be

Discussion

34.	An ideal gas is filled in an insulated cylinder fitted with a movable piston connected with an ideal spring (of force constant K) as shown in the figure. Initially, the spring is relaxed and the gas in the piston has volume V0 and temperature T0 . Now the gas in the cylinder is heated slowly so that the piston slides towards right to a distance x. Find the final pressure and temperature of the gas. (Given atmospheric pressure = P0 and area of cross-section of the cylinder is A).
Answer» An ideal gas is filled in an insulated cylinder fitted with a movable piston connected with an ideal spring (of force constant $K$ ) as shown in the figure. Initially, the spring is relaxed and the gas in the piston has volume $V_{0}$ and temperature $T_{0}$ . Now the gas in the cylinder is heated slowly so that the piston slides towards right to a distance $x$ . Find the final pressure and temperature of the gas. (Given atmospheric pressure = $P_{0}$ and area of cross-section of the cylinder is $A$ ).

Discussion

35.	A bar magnet is tied to a string and hung from the ceiling. Gravitational force of attraction by the earth is pulling the magnet down. According to Newton's first law, the magnet should move towards ground as it is acted upon by a force. Then why isn't it happening.
Answer» A bar magnet is tied to a string and hung from the ceiling. Gravitational force of attraction by the earth is pulling the magnet down. According to Newton's first law, the magnet should move towards ground as it is acted upon by a force. Then why isn't it happening.

Discussion

36.	The frequency of oscillation of an electric dipole moment having dipole moment p and rotational inertia I, oscillating in a uniform elctric field E is given
Answer» The frequency of oscillation of an electric dipole moment having dipole moment p and rotational inertia I, oscillating in a uniform elctric field E is given

Discussion

37.	The velocity of a particle is v=v0+ct+gt2. If its position is x=0 at t=0, then its displacement at time (t=2 sec) is
Answer» The velocity of a particle is $v = v_{0} + c t + g t^{2}$ . If its position is $x = 0$ at $t = 0$ , then its displacement at time $(t = 2 sec)$ is

Discussion

38.	An electron jumps from the 4th orbit to the 2nd orbit of hydrogen atom. Given the Rydberg's constant R=105 cm−1. The frequency in Hz of the emitted radiation will be
Answer» An electron jumps from the $4^{t h}$ orbit to the $2^{n d}$ orbit of hydrogen atom. Given the Rydberg's constant $R = 10^{5} c m^{- 1}$ . The frequency in Hz of the emitted radiation will be

Discussion

39.	A ring of radius R is charged uniformly with a charge +Q . The electric field at any point on its axis at a distance r from the circumference of the ring will be
Answer» A ring of radius $R$ is charged uniformly with a charge $+ Q$ . The electric field at any point on its axis at a distance $r$ from the circumference of the ring will be

Discussion

40.	A shell is fired from cannon with a velocity 'V' at an angle θ with the horizontal direction. At the highest point in its path, it explodes into two pieces of equal masses. One of the pieces retraces its path to the cannon. The speed of the other piece immediately after the explosion is
Answer» A shell is fired from cannon with a velocity 'V' at an angle $θ$ with the horizontal direction. At the highest point in its path, it explodes into two pieces of equal masses. One of the pieces retraces its path to the cannon. The speed of the other piece immediately after the explosion is

Discussion

41.	Consider a neutron and an electron bound to each other due to gravitational force. Assuming Bohr's quantization rule for angular momentum to be vaild in this case, derive an expression for the energy of the neutron -electron system.
Answer» Consider a neutron and an electron bound to each other due to gravitational force. Assuming Bohr's quantization rule for angular momentum to be vaild in this case, derive an expression for the energy of the neutron -electron system.

Discussion

42.	A charge particle having charge q is accelerated through a potential difference V and then it enters a perpendicular magnetic field in which it experiences a force F. If V is increased to 5V, the particle will experience a force
Answer» A charge particle having charge q is accelerated through a potential difference V and then it enters a perpendicular magnetic field in which it experiences a force F. If V is increased to 5V, the particle will experience a force

Discussion

43.	The friction coefficient between the horizontal surface and each of the blocks shown in figure is 0.20. The collision between the blocks is perfectly elastic. Find the separation between the two blocks when they come to rest. Take g = 10 m/s2.
Answer» The friction coefficient between the horizontal surface and each of the blocks shown in figure is 0.20. The collision between the blocks is perfectly elastic. Find the separation between the two blocks when they come to rest. Take $g$ = 10 $m / s^{2}$ .

43.

The friction coefficient between the horizontal surface and each of the blocks shown in figure is 0.20. The collision between the blocks is perfectly elastic. Find the separation between the two blocks when they come to rest. Take g = 10 m/s2.

Answer»

The friction coefficient between the horizontal surface and each of the blocks shown in figure is 0.20. The collision between the blocks is perfectly elastic. Find the separation between the two blocks when they come to rest. Take $g$ = 10 $m / s^{2}$ .

Discussion

44.	A projectile is fired at an angle of 450 with the horizontal. Elevation angle of the projectile at its highest point as seen from the point of projection is
Answer» A projectile is fired at an angle of $45^{0}$ with the horizontal. Elevation angle of the projectile at its highest point as seen from the point of projection is

Discussion

45.	Find the equation of trajectory of projectile projected at an angle 60 and has an initial velocity of 2 ms−1.
Answer» Find the equation of trajectory of projectile projected at an angle 60 and has an initial velocity of 2 $m s^{- 1}$ .

Discussion

46.	A small block of mass m is lying at rest at point P of a wedge having a smooth semi circular track of radius R. The minimum value of horizontal acceleration ao of wedge so that mass can just reach the point Q?
Answer» A small block of mass m is lying at rest at point P of a wedge having a smooth semi circular track of radius R. The minimum value of horizontal acceleration $a_{o}$ of wedge so that mass can just reach the point Q?

46.

A small block of mass m is lying at rest at point P of a wedge having a smooth semi circular track of radius R. The minimum value of horizontal acceleration ao of wedge so that mass can just reach the point Q?

Answer»

A small block of mass m is lying at rest at point P of a wedge having a smooth semi circular track of radius R. The minimum value of horizontal acceleration $a_{o}$ of wedge so that mass can just reach the point Q?

Discussion

47.	Separation between the plates of a parallel plate capacitor is and the area of each plate is A. When a slab of material of dielectric constant and thickness t(t<d) is introduced between the plates, its capacitance becomes
Answer» Separation between the plates of a parallel plate capacitor is and the area of each plate is A. When a slab of material of dielectric constant and thickness t(t<d) is introduced between the plates, its capacitance becomes

Discussion

48.	The de Broglie wavelength of a particle with mass 1 g and velocity 100 m/s is
Answer» The de Broglie wavelength of a particle with mass 1 g and velocity 100 m/s is

Discussion

49.	Find →A.→B
Answer» Find $\to A . \to B$

49.

Find →A.→B

Answer»

Find $\to A . \to B$

Discussion

50.	A bullet of mass 10 g moving horizontally with a velocity of 400 m/s strikes a wooden block of mass 2 kg which is suspended by a light inextensible string of length 5 m. As a result, the centre of gravity of the block is found to rise a vertical distance of 10 cm. The speed of the bullet after it emerges out horizontally from the block will be
Answer» A bullet of mass $10 g$ moving horizontally with a velocity of $400 m / s$ strikes a wooden block of mass $2 k g$ which is suspended by a light inextensible string of length $5 m$ . As a result, the centre of gravity of the block is found to rise a vertical distance of $10 c m$ . The speed of the bullet after it emerges out horizontally from the block will be

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Three blocks m1,m2 and m3 of masses 8 kg,3 kg and 1 kg are placed in contact on a smooth surface. Forces F1=140 N and F2=20 N are acting on blocks m1 and m3 respectively as shown. The reaction between blocks m2 and m3 is

What should be the pressure inside a air bubble of radius 0.1 mm situated 1 m below the water surface? (Take surface tension of water T=7.2×10−2 N/m and g=10 m/s2)

Why work done by pseudo force always negative?

The length of a simple pendulum executing simple harmonic motion is increased by 10%. The percentage increase in the time period of the pendulum due to increased length will be:

State and prove Newton's law of Cooling.Also show the cooling curve.

A body of mass 1 kg travelling due East with 3 m/s turns due North to travel with the same velocity. Find the net force exerted on the body for it to turn if it takes 0.01 sec to turn

Number of electric lines of force from 0.5 C of positive charge in a dielectric medium of dielectric constant 10 is

A 5.0 diopter lens forms a virtual image which is 4 times the object placed perpendicularly on the principal axis of the lens. Find the distance of the object from the lens.

Two 120V Light bulbs, one of 25W and other of 200W are connected on series across a 240V line. One bulb burnt instantly. Which one was burnt and why? Explain

The direct conversion of A to B is difficult, hence it is carried out by the following shown path: C ⟶ D ↑A ↓B Given ΔS(A→C) = 50 e.u.,ΔS(C→D) = 30 e.u., ΔS(B→D) = 20 e.u., where e.u. is the entropy unit, then ΔS(A→B) is

Why skin effect is shown by AC and not by DC?

The ratio of the energies of photons of 2000Å to that of 4000Å is

Four like charges each of +q are placed at the corners of a square of side a. The electric field intensity at the centre of square will be:

A person A pushes a body of 5 kg placed on a rough surface of co-efficient of friction 0.3 by a distance of 4 m in 15 seconds. Another person B pushes the body of 7 kg on same surface by a distance of 3 m in the same time. Who has more energy and power?

In a circus stuntman rides a motorbike in a circular track of radius R in the vertical plane. The minimum speed at highest point of track will be

A photoelectric cell is illuminated by a point source of light 1 m away. When the source is shifted to 2 m then

The power of a pump, which can pump 200kg of water to a height of 200m in 10sec is (g=10m/s−2)

Identify the electromagnetic waves whose wavelengths vary as (a) 10−12m&lt;λ&lt;10−8m (b) 10−3m&lt;λ&lt;10−1m Write one use for each.

In a common-emitter amplifier, using output resistance of 5000 ohm and input resistance of 2000 ohm, if the peak value of input signal voltage is 10 mV and β=50, then the power gain is

Draw a labelled ray diagram of a refracting telescope. Define its magnifying power and write the expression for it. Write two important limitations of a refracting telescope over a reflecting type telescope.

An object is to be seen through a simple microscope of focal length 12 cm. Where should the object be placed so as to produce maximum angular magnification? The least distance for clear vision is 25 cm.

A projectile is thrown with a speed of 100 m/s making an angle of 60∘ with the horizontal. Find the minimum time after which its inclination with the horizontal is 45∘.

A particle starts with some initial velocity and covers x1 distance with a1 acceleration and further x2 distance with a2 acceleration. If the final velocity is same as initial velocity then

For a gas, the r.m.s. speed at 800 K is

Which of the following expressions represent simple harmonic motion [Roorkee 1999]

How much heat energy is gained when 5 kg of water at 20∘C is brought to its boiling point? (Specific heat of water=4.2 kJ kg−1c−1)

Find the charge on each of the capacitors 0.20 ms after the switch S is closed in figure (32-E34).

The rate of radiation of a black body at 0o C is E J/sec. The rate of radiation of this black body at 273o C will be

A bar magnet is tied to a string and hung from the ceiling. Gravitational force of attraction by the earth is pulling the magnet down. According to Newton's first law, the magnet should move towards ground as it is acted upon by a force. Then why isn't it happening.

The frequency of oscillation of an electric dipole moment having dipole moment p and rotational inertia I, oscillating in a uniform elctric field E is given

The velocity of a particle is v=v0+ct+gt2. If its position is x=0 at t=0, then its displacement at time (t=2 sec) is

An electron jumps from the 4th orbit to the 2nd orbit of hydrogen atom. Given the Rydberg's constant R=105 cm−1. The frequency in Hz of the emitted radiation will be

A ring of radius R is charged uniformly with a charge +Q . The electric field at any point on its axis at a distance r from the circumference of the ring will be

A shell is fired from cannon with a velocity 'V' at an angle θ with the horizontal direction. At the highest point in its path, it explodes into two pieces of equal masses. One of the pieces retraces its path to the cannon. The speed of the other piece immediately after the explosion is

Consider a neutron and an electron bound to each other due to gravitational force. Assuming Bohr's quantization rule for angular momentum to be vaild in this case, derive an expression for the energy of the neutron -electron system.

A charge particle having charge q is accelerated through a potential difference V and then it enters a perpendicular magnetic field in which it experiences a force F. If V is increased to 5V, the particle will experience a force

The friction coefficient between the horizontal surface and each of the blocks shown in figure is 0.20. The collision between the blocks is perfectly elastic. Find the separation between the two blocks when they come to rest. Take g = 10 m/s2.

A projectile is fired at an angle of 450 with the horizontal. Elevation angle of the projectile at its highest point as seen from the point of projection is

Find the equation of trajectory of projectile projected at an angle 60 and has an initial velocity of 2 ms−1.

A small block of mass m is lying at rest at point P of a wedge having a smooth semi circular track of radius R. The minimum value of horizontal acceleration ao of wedge so that mass can just reach the point Q?

Separation between the plates of a parallel plate capacitor is and the area of each plate is A. When a slab of material of dielectric constant and thickness t(t&lt;d) is introduced between the plates, its capacitance becomes

The de Broglie wavelength of a particle with mass 1 g and velocity 100 m/s is

Find →A.→B

Identify the electromagnetic waves whose wavelengths vary as (a) 10−12m<λ<10−8m (b) 10−3m<λ<10−1m Write one use for each.

Separation between the plates of a parallel plate capacitor is and the area of each plate is A. When a slab of material of dielectric constant and thickness t(t<d) is introduced between the plates, its capacitance becomes