VISWA NIKETAN SECONDARY SCHOOL
Tripureswor, Kathmandu
Questions Bank (A)
XI - SCIENCE
PHYSICS XI - SET A
Group „A‟
1. Answer, in brief, any six questions. 6x2=12
a. Taking force, length and time to be fundamental quantities, find the dimensions of
pressure and density.
b. A car moving from a station P to another station Q and then back to P with uniform
speed of 60km/hr. What are the average speed and velocity of the car? Explain your
answer.
c. If a man wants to hit a target, in what direction should he point his rifle?
d. Why are vehicles provided with wheels and ball bearings?
e. No energy is consumed in planetary motion, why? Explain.
f. Why is the highway roads banked at turning?
g. Explain why is the earth flattened at the poles?
2. Answer, in brief, any two questions. 2x2=4
a. Explain why is platinium wire used in resistance thermometer?
b. Is it possible to heat substance without rise in temperature?
c. Absolute zero temperature is not the zero energy temperature, explain.
3. Answer, in brief, any one question. 1x2=2
a. What is refractive index? On which factors does it depend?
b. What are the advantages of the total reflecting prism over than plane mirror?
4. Answer, in brief, any one question. 1x2=2
a. Define action of points. Also write its two uses.
b. The relative permittivity of water is 80. What does it mean?
Group „B‟
5. Answer any three questions. 3x4=12a. State and prove parallelogram law of vector addition.
b. State Newton‟s first and second law of motion. Also prove that, first law gives the
definition of force and second law gives the measurement of force.
c. Show that the total mechanical energy of a body is conserved when it moves under
the gravitational field.
d. Derive an expression for the change in the value of acceleration due to gravity at a
place of latitude of the rotation of earth.
6. Answer any two questions. 2x4=8
a. Describe how the cubical expansivity of a liquid can be determined by the use of
balanced columns.
b. State Newton‟s law of cooling. Also determine the specific heat of liquid by method
of cooling.
c. What do you mean by ideal or perfect gas? Also derive the equation of state PV =nRT
7. Answer any one question. 1x4=4
a. Derive mirror formula for convex mirror.
b. Derive the relation between refractive index and minimum deviation of a prism.
8. Answer any one question. 1x4=4
a. Define charge. How a body be charged positively by induction?
b. Define electric lines and electric flux. Also derive an expression for the flux due to a
point charge +q.
Group „C‟
9. Answer any three numerical questions. 3x4=12a. Rain is falling vertically downward with a speed of 10km/s. A man runs on a
horizontal road at 60km/s in the rain. (i) At what angle should he hold the umbrella in
order to protect himself from the rain? (ii) What is the velocity of rain relative to the
man?
b. How long will it take for wooden block of mass 2kg to slide from rest to distance of
3cm down a rough plane inclined at 30o
to the horizontal? [=0.2]
c. A mass of 0.2kg is whirled in a horizontal circle of radius 0.5m by a string inclined to
30o
to the vertical. Calculate tension in the string and the speed of mass in the
horizontal circle.
d. The mass of the earth is 6x1024kg and that of the moon is 7.4x1022k. If the distance
between their centers is 3.8x108m. Calculate at what point on the line joining their
centers, there is no gravitational forces?
10. Answer any two numerical questions. 2x4=8
a. A brass rod and steel rod differ by 10cm in length at all temperatures. What are their
lengths at 0oC?(b=1.8x10-6C
-1
, s =12x10-6C
-1
)
b. From what height should a block of ice be dropped in order that it may completely
melt? It is assumed that only 20% of energy is retained by ice.
c. For what mass of molecule of a particle is vrms equal to 1m/s at a temperature of 27oC.
11. A convex lens of focal length 24cm (ag =1.5) is totally immersed in water (aw =1.33).
Find the focal length in water.
4
12. Two small spheres spaced 20cm apart have equal charge. How many excess electrons
must be present on each sphere if the magnitude of the two force of repulsion between
them is 4.57x10-21N? ( Eo=8.85x10-12Fm-1
)
3
PHYSICS XI - SET B
Group „A‟1. Answer, in brief, any six questions. 6x2=12
a. Define significant figure of a number.
b. A physical quantity has both magnitude and direction. Is the quantity necessarily a
vector? Justify your answer.
c. Under what condition is the average velocity equal to the instantaneous velocity?
d. It is easier to pull than to push a lawn roller, why?
e. What are conservative and non-conservative forces?
f. Why a force is necessary to keep a body moving with uniform speed in a circular
motion?
g. The weight of a body is less in mine. Is it true? Explain.
2. Answer, in brief, any two questions. 2x2=4
a. How are gas thermometers superior to mercury thermometers?
b. What are the limitations of Newton‟s law of cooling?
c. Why are the gas law not obeyed at low temperature and high pressure?
3. Answer, in brief, any one question. 1x2=2
a. Does the size of the mirror affect the nature of the image?
b. If a convex lens is immersed in water, does it power change?
4. Answer, in brief, any one question. 1x2=2
a. Can a charged body attract an uncharged body? Explain.
b. Two electric lines never intersect each other. Comment it?
Group „B‟
5. Answer any three questions. 3x4=12a. From velocity – time graph, derive the following kinematics equation of motion:
i) v=u+at (ii) v
2
=u
2
+2as
The symbols have their usual meanings.
b. State Newton‟s second law of motion and prove that impulse is equal to change in
momentum.
c. State and prove work energy theorem.
d. What do mean by geostationary satellite and parking orbits? Derive an expression for
the total energy of a satellite in a circular orbit.
6. Answer any two questions. 2x4=8
a. Define linear expansivity of a solid. Describe a method to determine the linear
expansivity of a solid.
b. What is heat capacity? Describe the method of mixture to determine the specific heat
of a solid.
c. Prove that the pressure exerted by the gas on the walls of a container is 2/3 times the
translation kinetic energy per unit volume.
7. Answer any one question. 1x4=4
a. Show that the angle of deviation for small angled prism is independent with the angle
of incidence.
b. Show that the combined power of lens is the sum of power of individual lenses when
placed in contact.
8. Answer any one question. 1x4=4
c. State and explain Coulomb‟s law in electrostatics. Mention two similarities and
dissimilarities between electrostatic and gravitational forces.
a. Define electric field and electric field intensity. Calculate the electric field intensity
due to a point charge.
Group „C‟
9. Answer any three numerical questions. 3x4=12a. Find the velocity and direction of projection of a shot which passes in a horizontal
direction just over the top of a wall which is 50m off and 25m high.
b. A man of mass 70kg stands on a weighing machine inside an elevator. What is the
uniform speed, (iii) the elevator accelerates upwards at a 5m/s2
and (iv) the elevator
accelerates downwards at 5m/s2
?
c. A rifle bullet weighing 20gm is fired with a velocity 91m/s into a wooden block of
mass 1.8kg which is suspended from a cord of 1m long. If the bullet embeds itself
inside the block. Calculate the vertical height through which the pendulum rises and
the maximum inclination of the cord to the vertical.
d. A stone is rotated steadily in a horizontal circle with a period T by a string of length
L. If the tension in the string is constant and L increases by 1%. Find the percentage
change in T?
10. Answer any two numerical questions. 2x4=8
a. The pendulum clock is made of brass whose linear expansivity is 1.9x10-5C
-1
. If the
clock keeps correct time at 15oC, how many seconds per day will it lost at 20oC?
b. An electric heater supplies heat at the constant rate. It takes 15min to raise a certain
amount of water from 0oC to boiling using a heater. Then it takes 1hr and 20min more
to convert all the water into vapour. Find the specific latent heat of vaporization of water.
c. 14gm of nitrogen, 32gm of oxygen and 2gm of hydrogen are placed in an enclosure
of volume 1cm3
. Calculate the pressure exerted by the mixture at 27oC.
11. A light travelling in air is incident on the surface of a block of plastic at an angle of 62.7o
to the normal and is deviated through an angle 48.7o with the normal in a plastic. Find the
speed of light in the plastic.
12. Two positive charges are 0.1 m apart and exert a repulsive force of 18N on each other. If
total charge of these two is 9C. Find the value of each other. (o=8.85x10-12Fm-1
)
13. Second Terminal Examination (2070)
PHYSICS XI - SET C
1. Attempt any six questions [2x6=12]a. Explain when a passenger throws a ball upwards inside the moving bus, the ball returns
on his hand
b .A man moving in rain holds his umbrella inclined to the vertical even though the rain
drops are falling vertically downwards. Why ?
c. Find the angle of projection at which the maximum height and horizontal range of a
projectile are equal
d. Can action and reaction forces cancel each other ?
e. It is easier to pull a body than to push it. Why ?
f. Can a body have energy with out having momentum? explain.
g. Explain why a boat lightly moves away from the shore when a person from it jumps to
the shore ?
h. A light body and a heavy body have the same kinetic energy , which one will have
agreater momentum?
2. Attempt any two questions [2x2=4]
a. Why do animal eat more during winter ?
b. Explain, why is food cooked faster in a pressure cooker than in an open pot.
c. Why can you get more sever burn from steam at 100oC than from water at 100oC?
3. Attempt any one question [1x2=2]
a. Why does the star twinkle in the sky ?
b. When write light is dispersed by a prism, red light appears at the top of the spectrum
whereas violet at the bottom. Why ?
4. Attempt any one question [1x2=2]
a. Why pointed ends are not kept in electrostatic machine ?
b. Two electric lines of force never intersect each other. Why ?
Group A [Longt Questions]
5. Attempt any Three questions [3x4=12]a. Define projectile. Show that the path of a projectile projected making an angle with
horizontal is parabolic.
b. State the principle of conservation of energy. Show that mechanical energy remains
constant for a falling body.
c. What are the laws of limiting friction ? Show that the coefficient of limiting friction is
equal to the tangent of angle of repose .
d. State and explain the parallelogram law of vector addition.
6. Attempt any Two questions [2x4=8]
a. Describe Dulong and Petit's experiment to find out the coefficient of real expansion of
liquid.
b.. Derive the equation of state for an ideal gas.
c . Explain the method of mixture for finding specific heat capacity of solid.
7. Attempt any One questions [1x4=4]
a. What do mean by chromatic aberration ?derive the condition for achromatism lenses in
contact
b. What is lateral shift ? Deduce lateral shift in terms of thickness of a slab and the angle of
incidence of light
8. Attempt any One questions [1x4=4]
a. What is meant by electrostatic induction ? Show how you would charge a body positively
by induction.
b. State &explain gauss theorem use it to find the electric field due t a charged conducting sphere.
Group C [Numerical Problems]
9. Attempt any Three questions [3x4=12]
a. An iron block of mass 10 kg, rests on a wooden plane inclined at 300
to the horizontal. It
is found that least force parallel to the plane which causes the block to slide yp the plane
is 100N. Calculate the coefficient of sliding friction between wood and iron
(g=10m/s2
)
b. A fire engine pumps water such a rate that the velocity of the water leaving the nozzle is
15m/s. If the jet be directed perpendicularly on to a wall and the rebound of the water be
neglected, calculate the pressure on the wall. (1m3 water has mass 1000kg)
c. A railway truck of mass 4x104
kg moving at a velocity of 3m/s collides with another
truck of mass 2x104
kg which is at rest. The coupling joins and the trucks move off
together. What traction of the first truck's initial K.E. remains as K.E. of the two trucks
after the collision ?
d. How fast would a 70 kg person have to run to have the energy equal to the energy given
by 100 W light bulb per hour?
10. Attempt any Two questions [2x4=8]
a. A clock whose pendulum makes one vibration in 2 seconds is correct 25C how many
seconds per day will clock gain or lose at 15C
b. What is the result of mixing 20 gm of water at 900
c with 10 gm of ice at -100
c ? (Specific
heat of ice = 0.5 cal/gmc latent heat of ice = 80 cal /gm)
c. The density of silver at 00
c is 10310 kgm-3
and the coefficient of linear expansion 19 x
10-6
/
0
c. Calculate its density at 1000
c.
11. It is desired to make a converging achromatic lens of mean focal length 40 cm by using two
lenses of materials A and B. If dispersive powers of A and B are in the ratio 1/3, find the
focal lengths of each lens . [4]
12.. Calculate the value of two equal charges if they repel one another with the force of 0.1N
when situated 50cm a part in vaccum. What would be the amount of charges if they were
situated in an insulating liquid whose permittivity was 10 times that of vaccum.
[3]
PHYSICS XI - SET D
Group A
1. Answer in brief any six. 62=12(a) Using the method of dimensions, derive an expression for the centripetal force facing on
an particle of mass „m‟ moving with velocity „v‟ in a circle of radius „r‟.
(b) Can the sum of two equal vectors be equal to either of the vectors explain.
(c) Find the angle of projection for which the horizontal range and maximum height of
projection are equal.
(d) Why is it difficult to move a bike with its brakes on?
(e) How does the K.E. of an object change if its momentum is doubled.
(f) Why a critter lowers his hands while catching a ball ?
(g)why has a horse to pull a cart harder during the first few steps of its motion ?
(h) Is there any work done by the car if it moves with uniform speed on a smooth level road ?
2. Answer in brief any two 22=4
(a) Why does a thick tumbler crack when boiling water is poured on it?
(b) Why can you get more sever burn from steam at 100oC than from water at 100oC?
(c) Why do animal eat more during winter
3. Answer in brief any one 2x1=2
a. Will the focal length of a lens increase or decrease when it is immersed in water ?
b. When write light is dispersed by a prism, red light appears at the top of the spectrum
whereas violet at the bottom. Why ?
4. Answer in brief any ONE 2x1=2
a. A charged conical conductor loses its charge earlier than a similarly charged sphere. Why
?
b. Two electric lines of force never intersect each other. Why ?
5. Answer in any three 34=12
(a) State the principle of conservation of energy. Show that total mechanical energy remains
same for a freely falling body.
(b) State and explain the triangle law of vector addition.
(c) Define work. Derive an expression to calculate the work done by avariable force.
(d) Show that a stone projected at an angle with the horizontal follows a parabolic path.
Also calculate its time of flight.
6. Answer any two questions. 24=8
(a) Define latent heat of fusion of ice. Describe a method to determine it by the method of
mixture.
(b) Derive the equation of state for an ideal gas.
(c) Describe Dulong and Petit‟s experiment to find the coefficient of real expansion of liquid.
7. Answer any onequestions. 24=8
(a) Show that the deviation produced by a small angled prism is independent with angle of
incidence.
(b) Derive the formula for the power of two thin lenses in contact.
8. Answer any onequestions. 24=8
a. What is meant by electrostatic induction ? Show how you would charge a body positively
by induction.
b. Derive the relation for electric field intensity at a point.
9. Answer any three. 34=12
(a) A bullet of mass 10g traveling horizontally with a velocity of 300m/s strikes a block of
wood of mass 290g which rests on a rough horizontal floor .After impact ,the block and
bullet move together and come to rest when the block has travaledadistance of 15m.
Calculate the coefficient of friction between the block and the floor.
(b) How fast would a 70 kg person have to run to have the energy equal to the energy given
by 100 W light bulb per hour?
(c) The mass of a gas emitted from the rear of toy rocket is initially 0.1 kg/s if the speed of
the gas relative to the rocket is 50m/s and the mass of the rocket is 2kg,what is the
initial acceleration of the rocket ?
(d) A body is projected horizontally from a top of tower 100m high with a constant velocity
of 9.8 m/l. Find the velocity with which it hits the ground.
10. Answer any two questions. 24=8
(a) A litre of air initially at 20oC and at 760 mm of Hg is heated at constant pressure until its
volume is doubled. Find the final temperature.
(b) What is the result of mixing 100 gm of ice at 0oC into 100 gm of water at 20oC in an iron
vessel of mass 100 gm? (specific heat of iron 0.1 cal gm-1
c
-1
)
(c) The density of silver at 0oC is 10310 kgm-3
and the coefficient of linear expansion is 19
10-6
/
oC. Calculate the density of silver at 50oC.
11. Calculate the focal length of a lens of dispersive power 0.031 which should be placed in
contact with a convex lens of focal length 84 cm and dispersive power 0.021 to make the
achromatic combination. 3
12. calculate the value of two equal charges if they repel one another with the force of
0.1N when situated 50cm a part in vaccum. What would be the amount of charges if they
were situated in an insulating liquid whose permittivity was 10 times that of vaccum.
PHYSICS XI - SET E
1. Answer, in brief, any six questions: [6 x 2 = 12]a) Taking force, length and time to be fundamental quantities, find the dimensions of
gravitational constant.
b) A ball is projected horizontally from the top of a building and another is dropped with
zero velocity from the same point at the same time, which one will hit the ground
first?
c) If your hands are wet and no towel is handy, you can remove some of the excess
water by shaking them. Why does this get rid of the water?
d) Why is chinaware wrapped in straw or paper before packing them?
e) A planet has mass 2 times that of Earth and radius 3 times that of Earth. Calculate 'g'
for that planet. [g for Earth = 10m/s2
].
f) A fresh egg sinks in water but floats in a saturated solution of salt. Explain.
g) Why do machine parts or engines get jammed in winter?
2. Answer, in brief, any two questions: [2 x 2 = 4]
a) During winter water pipes burst, why? Would the mercury thermometer break if the
temperature went below the freezing temperature of mercury? Why or why not?
b) Two different gases are at same temperature. What can be said about their rms speed
and average kinetic energy?
c) What is relative humidity? Why is its value more near sea water?
3. Answer, in brief, any one question. [1 x 2 = 2]
a) Why does the sun look a little oval when it is at the horizon?
b) Define the terms: lumen and lux.
4. Answer, in brief, any one question. [1 x 2 = 2]
a) What do you understand by electric flux through an area in an electric field? State the
condition for minimum and maximum value of it.
b) Dielectric constant of water is 80. What does it mean?
Group B
5. Answer all questions: [3 x 4 = 12]
a. A projectile is fired from the ground at an angle and with a velocity u. Show
that its path is a parabola. Also calculate its time of flight and horizontal range.
b. State and prove principle of conservation of linear momentum for a system of two
colliding bodies.
c. What is a satellite? Derive an expression for the orbital velocity and hence find
the expression for the time period of the satellite revolving around the earth.
d. Derive an expression for the elastic potential energy stored in a stretched wire.
Define the term energy density of a body under strain.
e. Define surface energy. Show that the surface tension is numerically equal to the
surface energy.
6. Answer all questions: [2 x 4 = 8]
a) Define specific heat capacity of a substance. How do you measure the specific heat
capacity of solid by the method of mixture?
b) Derive the relationship between the density, total pressure and the rms speed of the
gas molecules ie
2
3
1 P c
.
7. Define real and apparent depth . Deduce the relation.
Apparent Depth
Real Depth
, where is refractive index of medium.
8. State Gauss law. Use it to find electric field intensity due to a charged metal sphere at any
point outside the sphere. [4]
Group C
9. Answer all questions: [3 x 4 = 12]
a) Two tall buildings are 40m apart. With what speed must a ball be thrown horizontally
from a window 120m above the ground in one building so that it will enter a window
40m from the ground in the other.
b) Find the acceleration and tension in the cord for the following system. Assume that
the pulley is frictionless.
c) An ice berg has a volume of 100m3
. Calculate its volume that can be seen above the
surface of a sea. Density of sea water and ice are 1030kgm-3
and 920kgm-3
.
OR
The terminal velocity of a copper ball of radius 2.0mm falling through a tank of oil at
200C is 6.5cm s-1
Compute the viscosity of the oil at 200C. Density of oil = 1.5 x 103
kgm-3
, density of
copper = 8.9 x 103
kgm-3
.
10. Answer all questions: [2 x 4 = 8]
a) A silica bulb of negligible expansivity holds 340gm of mercury at 00C when full.
Some steel balls are introduced and remaining space is occupied at 00C by 255 gm of
mercury. On heating the bulb and its contents to 1000C, 4.8gm of mercury overflow.
Find the linear expansivity of the steel.
[Linear expansivity of mercury Ξ³Hg = 180 x 10-60C -1
].
b) There is 38gm of oxygen gas in vessel at 270C. Calculate the total kinetic energy of
its molecules.
11. What is the apparent position of an object below a rectangular block of glass 6cm thick if
a layer of water 4cm thick is on top of the glass? [Refractive index of glass and water =
3/2 and 4/3 respectively. [4]
12. Two point charges -1c and 2c are kept in two corners A and B respectively of
equilateral triangle ABC of side 3cm. Calculate the resultant field intensity when the
whole system is in air.[3]
PHYSICS XI - SET F
Group „A‟
1. Answer in brief, any SIX questions: [6x2=12](a) A student writes
π
2πΊπ
for the escape velocity, where R is radius and M is mass of
the earth, and G is gravitational constant. Check the correctness of the formula by
using dimensional analysis.
(b) Can the flight of a bird be an example of composition of vectors?
(c) The sum and difference of two vectors are equal in magnitude. Prove that the
vectors are perpendicular to each other.
(d) Find the angle of projection at which the horizontal range and maximum height of a
projectile are equal.
(e) Why is it easier to pull a body than to push it?
(f) A fan with blades takes longer time to come to rest than without the blades. Why?
(g) Does the centre of mass of a body always lie within the body? Explain with example.
(h) Hot soup is tastier than cold soup. Why?
2. Answer in brief, any TWO questions: [2
2=4]
(a) Does the coefficient of linear expansion depend on length? Explain.
(b) A red hot iron is thrust into boiling water. Does the temperature of water increase or
decrease?
(c) Why latent heat of vaporization of a liquid is greater than that of latent heat of
fusion?
3. Answer in brief, any ONE question: [1
2=2]
(a) You are given a lens through you can see but you are not allowed to touch. How
would you find whether it is convex or concave? Justify.
(b) A ray of light in air strikes a glass surface. Is there a range of angles for which total
internal reflection takes place?
4. Answer in brief, any ONE question: [1
2=2]
(a) Why are the tyres of air craft's made slightly conducting?
(b) An electric line of force is a continuous curve i.e. a line of force cannot have sudden
breaks, why?
Group „B‟
5. Answer any THREE questions: [3
4=12]
(a) State and prove the principle of conservation of linear momentum.
(b) What are the laws of friction? How they are experimentally verified?
(c) Derive an expression for the elastic potential energy stored in a stretched wire.
Define the term energy density of a body under strain.
(d) Explain the meaning of the term 'moment of inertia'. Derive an expression for total
energy of an object rolling down a plane.
OR, Define surface energy. Show that the surface tension is numerically equal to the
surface energy.
6. Answer any TWO questions: [2
4=8]
(a) Define specific heat capacity of a substance. Describe the method of mixture to
determine the specific heat capacity of solid.
(b) What is latent heat of fusion of ice? Develop an expression for the determination of
the latent heat of fusion of ice.
(c) Derive ideal gas equation for n moles of gas. Also write the unit and physical
significance of molar gas constant.
7. Answer any ONE question: [1
4=4]
(a) Deduce the relation, refractive index () = π ππππ·πππ‘ β
π΄πππππππ‘π·πππ‘ β
. What do you mean by
apparent shift?
(b) Define power of lens with its unit. Show that for two thin lenses in contact, the
effective focal length is given by,
1
πΉ
=
1
π1
+
1
π2
. Where symbols have their usual meanings.
8. Answer any ONE question: [1
4=4]
(a) Define electric potential. Derive an expression for the potential at a point due to a
point charge.
(b) State and explain Gauss's theorem in electrostatics and use it to find the electric field
intensity due to a hollow charged spherical conductor.
Group „C'
9. Solve any THREE numerical questions: [3
4=12]
(a) A football player kicks a ball lying on the ground level with a velocity of 20 m/s at
an angle of 30o
above the ground. A second player, standing at a distance of 50m
from the first, runs to kick the ball at the instant the first player kicked off. How fast
the second player must run to kick the ball just before it touches the ground?
(b) The mass of gas emitted from the rear of a toy rocket is initially 0.1kg/s. If the speed
of the gas relative to the rocket is 50m/s and the mass of the rocket is 2kg, what is
the initial acceleration of the rocket?
(c) A horizontal disc rotating freely about a vertical axis makes 100 rpm. A small piece
of wax of mass 10gm falls vertically on to the disc and adhere to it at a distance of
9cm from the axis. If the number of revolutions per minute is thereby reduced to 90,
calculate the moment of inertia of the disc.
OR, Find the work required to break up a drop of water of radius 0.5cm into drops of
water each of radii 1mm. The surface tension of water is 7 x 10 –2 N/ m.
(d) A wooden plank 3m x 2m x 0.5m is floating in water. Find the volume of plank
under water. How many persons each weighing 80Kg can the plank support?
[Density of wood = 600kgm–3
and density of water = 1000Kgm–3
]
10. Attempt any TWO numerical questions:[2x4=8]
(a) A steel wire 8m long and 4mm in diameter is fixed to two rigid supports. Calculate
the increase in tension when the temperature falls by 10oC. [Linear expansivity of
steel = 12 x 10-6 oC
-1
, Young's modulus for steel = 2 x 1011 N/m2
.]
(b) A body initially at 100oC cools to 60oC in 5 minutes and to 40oC in 10 minutes.
What is the temperature of surrounding? What will be the temperature in 15
minutes?
(c) A thermo flask contains 200gm of water and 10gm of ice at 0oC. 50gm of steam is
passed to the flask. What is the final result? (Assume no heat loss to the flask)
[Latent heat of fusion of ice = 80cal/gm, Latent heat of steam = 540cal/gm, specific
heat capacity of water = 1 calgm-1oC
-1
.]
11. A narrow beam of light is incident normally on one face of an equilateral prism
(refractive index 1.45) and finally emerges from the prism. The prism is now surrounded
by water (refractive index 1.33). What is the angle between the directions of the
emergent beam in two cases? [4]
12. Three charges 3 x 10-9C, –3 x 10-9C and 1.5 x 10-9C are placed in air at the corners A,
B, C of an equilateral triangle ABC having each side 5cm. Find the force acting on the
charge 1.5 x 10-9C. [3]
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