DASHAIN VACATION HOMEWORK
Department of physics
Class 11
2074
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Use separate copy to do H.W (do not use rough , thin type of
copies.do not use loose sheet)
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Underline with pencil after each question
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Make your handwriting best.
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You are requested to bring H.W on first day of college. H.W will be
collected by CR. Students securing grade other than A and B will have to do H.W
again within seven days
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Please completely avoid coping H.W. Try to do yourself
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Prepare H.W very well so that it becomes useful in final term
examination.
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If there are any questions from untaught portion, you don't need to do
it.
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Do not aim to do all questions within few days, divide all questions with
your holidays and solve daily.
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Try your best to solve all the questions
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You can complete this H. W. within 15 days. Remaining 15 days are your
real holidays.
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Enjoy while doing homework, do not take it as burden.
MECHANICS
Short questions
1) Obtain the
dimension of specific heat capacity, latent heat, Universal gas constant,
coefficient of viscosity, modulus of elasticity and gravitational constant.
2) The density
of the gold is 19.3 gm/cc. Express its value in S.I unit.
3) Taking force,
length and time to be fundamental quantities find the dimensional formula for
mass, momentum, Universal Gravitational constant and density.
4) Check the correctness of the formula v2 =u2 +2as
using dimensional analysis.
5) Convert
10 ergs in joule.
6) Name any
three physical quantities which have same dimensions.
7) Can
a quantity have unit but no dimension? Explain.
8) Is
dimensionally correct equation necessarily be a correct physical relation?
Justify your relation.
9) T force F is
given in terms of time‘t’ and displacement ‘x’ by the equation F = AsinBx +
CsinDt. What is the dimension of D/B?
10) What are the
limitations of dimension analysis?
11) Convert
1N into dyne by using dimensional analysis.
12) Can
you tell the unit of a physical quantity from its dimensions.
13) Can
the sum of the two equal vectors be equal to either of the vectors? Explain.
14) What
should be the angle between the two vectors of some magnitude, so that their
resultant is equal to either of them?
15) Can the
resultant of three vectors be zero?
16) Is
pressure a vector? Why?
17) Should
a quantity having magnitude and direction be necessarily a vector? Give
example.
18) Why are
rubbers used as vibration absorbers?
19) Differentiate
between elasticity and plasticity.
20) Two
wires A and B have equal lengths and are made of same material. If the diameter
of wire A is twice that of wire B, which wire has the greater extension for a
given load?
21) Why are
rubbers used as vibration absorbers?
22) Differentiate
between elasticity and plasticity.
23) Two
wires A and B have equal lengths and are made up of same material. If the
diameter of wire A is twice that of wire B, which wire has the greater
extension for a given load?
24) Explain
why soldiers are ordered to break steps while crossing a bridge.
25) Compare
the mechanical properties of a steel cable, made by twisting many thin wires
together, with those of solid steel rod of the same diameter.
26) Explain
in terms of breaking stress why elephant has thicker legs as compared to human
beings?
28) Explain which one is more elastic-rubber or steel.
29) Why bridges are declared unsafeafter a long use?
30) At what
distance from the mean position is the K.E equal to P.E in S.H.M
31) A
pendulum clock is taken to moon. Will it gain or lose time?
32) How does the frequency vary with
amplitude?
34) A
pendulum clock is taken to the moon. Will it gain or lose time?
35) If the
length of simple pendulum increased by 4 times its original length, will its
time period change? If yes, by how much?
37) A
pendulum clock is in an elevator that descends at constant velocity. Does it
keep correct time? If the same clock is in an elevator in free fall, does it
keep correct time?
39) Why
does the mercury inside the capillary tube made of glass depress when dipped in
a reservoir of mercury?
40) Why
small drops of mercury are spherical and bigger drops oval in shape?
41) Hairs
of a brush spread out when it is dipped in the water and cling together as soon
as it is taken out from the water. Explain.
42) We use
towels to dry our body after taking a shower, why?
43) Small
particles of camphor dance on the surface of water. Why?
44) Hot
soup is tastier than the cold one. Why?
45) Why is
a soap solution a better cleansing agent than the ordinary water?
46) The tip
of the nib of the pen is spilt. Why?
47) What will be the
effect on value of acceleration due to gravity, if the earth stops to rotate?
Long Questions
1) Explain S.H.M.
Obtain an expression for energy of particle executing simple harmonic
2) What is simple
pendulum? Show that the motion of simple pendulum is simple harmonic. Also
deduce its time period.
3) Show that the
motion of loaded vertical spring is simple harmonic. Also find its time period.
4) Explain
characteristics of SHM.
5) State and explain
triangle law of vector addition.
6) State and explain
parallelogram law of vector addition.
7) what is hooks law?
Prove it experimentally.
8) Define young’s
modulus. Also derive and expression for energy stored in a wire and hence find
its energy density.
Numerical
1) Calculate
the period of oscillation of a simple pendulum of length 1.8 m with a bob of
mass 2.2 kg. If the bob of the pendulum is pulled aside a horizontal distance
of 20m and released. What will be the value of i) the K.E and ii) the velocity
of the bob at the lowest point of the swing.
2) The
displacement y of a mass vibrating with a simple harmonic motion is given by
y=20sin10πt. Where y is in millimeter and t is in second. What is: (i)
amplitude (ii) the period (iii) the velocity at
t=0.
(0.002m,
0.2s, 0.628m/s)
3) A
simple pendulum 4m long swings with an amplitude of 0.2m.Compute the velocity
of the pendulum at its lowest point and Compute its acceleration at the end of
its path.(0.316m/sec, 0.499m/s2)
4) A
simple pendulum 5m long swings with an amplitude 25cm. Find the velocity of the
pendulum at its lowest point and the acceleration at the end of its
path.
(0.35m/sec, 0.62m/s2)
5) Calculate
the period of the oscillation of a simple pendulum of length 1.8m with a bob of
mass 2.2kg. If the bob of this pendulum is pulled aside a horizontal distance
of 20cm and released. What will be the values of (I) the K.E. and (ii) the
velocity of the bob at the lowest point of the swing?
(0.243J, 0.47m/s)
6) A
simple pendulum 4m long swings with amplitude of 0.2m. Compute the velocity of
pendulum at its lowest point at its lowest point and its acceleration at
extreme ends. (0.32m/s, 0.5m/s2)
7) A
particle of mass 0.3kg vibrates with a period of 2 seconds. If its amplitude is
0.5m what is its maximum kinetic
energy?
(0.37J)
8) A
simple pendulum whose length is 1m oscillates 30 times per minute in a certain
place. What is the acceleration due to gravity
there?
(9.87m/s2)
9) A
pendulum has a period of 4.2 second, when the pendulum is shortened by 1m the
period is 3.7 second. From these measurements, calculate the acceleration of
free fall and the original length of the
pendulum. (10m/s2, 4.5m)
10) A
second pendulum is taken to the moon. If the time period on the surface of the
moon is 4.9 seconds, what will be the acceleration due to gravity of the moon?
Take acceleration due to gravity on the moon to be 1/6th that
of the
earth.
(1.63m/sec2)
11) A
simple pendulum has a period of 4.2s. When the pendulum is shortened by 1m, the
period is 3.7s. From these measurements, calculate the acceleration of free
fall g and the original length of the pendulum.
12) If the
pendulum is taken from the earth to the moon where the acceleration of free
falls is g/6, what relative change, if any occurs in the period
T?
(2.45:1)
13) A
tunnel is dug along the diameter of the earth. If a body is dropped through one
end, how much time it would take to reach another
end.
(42.3min)
14) A small
mass rests on a horizontal platform which vibrates in simple harmonic motion
with a period of 0.25s. Find the maximum amplitude of the motion which will
allow the mass to remain in contact with the platform throughout the
motion.
(0.0158m)
15) Calculate
the work done in stretching a steel wire 100cm in length end of cross sectional
area 0/03cm2, when a load is slowly applied without the elastic
limit being reached. (Y=3.5x1011N/m2)
(8.3x10-3J)
16) Find
the work done in stretching a wire of cross sectional area 0.01cm2 and
2m long through 0.1mm, if Y for the material of wire is 2x1011N/m2.
(5x10-4J)
17) A
uniform steel wire of density 7800kg/m3 weighs 16 gm and is
250cm. It lengthens by 1.2mm when a load of 80kg is applied. Calculate the
value of Young’s modulus for the steel and the energy stored in the
wire.
(2.0x1011N/m2, 4.8x10-2J)
18) A steel
wire of density 8000kg/m3 weighs 24gm and 250cm long. It
lengthens by 1.2mm when stretched by a force of 80N. Calculate the Young’s
modulus for the steel and the energy stored in the
wire.
(1.4x1011N/m2, 4.8x10-2J)
19) How
much force is required to punch a hole 1cm in diameter in a steel sheet 5mm
thick whose shearing strength is 2.76x108N/m2.
(4.3x104N)
20) Convert 10J into
erg.
21) The time period of
simple pendulum depend on mass, length and acceleration due to gravity. Find
the relation for time period.
HEAT AND THERMODYNAMICS
Short questions
1) How
are gas thermometers superior to mercury thermometers?
2) A
thermometer is laid out in direct sun light. Does this thermometer measure the
temperature of the air or the sun or what?
3) A
faulty thermometer has its fixed points marked 50 and 950. What
is the correct temperature in Celsius when this thermometer reads 590
4) Show
that, Celsius and Fahrenheit thermometer show the same reading at –400C.
5) Why
the column of mercury in a thermometer first descends slightly and then rises
when placed in a hot substance?
6) Why
is mercury mostly used as thermometric substance?
7) At
what temperature do Fahrenheit and Kelvin scale give the same readings?
8) Why
are glass windows possible to be cracked in very cold regions?
9) Why
measuring scale should be made up of insulators or metals whose coefficient of
linear expansion is small?
10) What do
you mean by coefficient of linear expansivity? Does it depend upon original
length?
11) Why is
sometimes possible to loosen caps on screw top bottles by dipping the cap
briefly in hot water?
12) Two
bodies of same material have the same external diameters and appearance but one
is solid and the other is hollow. When they are heated up to same temperature.
Is the overall expansion the same?
13) Two
bodies of same material have the same external diameters and appearance but one
is solid and the other is hollow. When they are heated by same amount of heat.
Is the overall expansion the same?
14) Why
does heat flow from a body at higher temperature to a body at lower
temperature?
15) Frozen
water pipes often burst; will a mercury thermometer break if the temperature of
the thermometer is brought below the freezing point of mercury?
16) Why are
the Polar Regions much cooler than the equatorial regions despite the fact that
the Polar Regions are periodically tilted towards sun?
17) Why
liquid does has apparent expansion?
18) A hole
of 1cm in diameter is drilled in a plate of steel at 200C. What
happens to the diameter of the hole as the steel is heated to 1000C?
Long Questions
1) Define
linear, superficial and cubical expansivity. Establish the relation between
them.
2) What
is cubical expansivity? How do you determine the cubical expansivity of liquid
by Dulong and Petit's method.
3) Define
the terms coefficient of real and apparent expansion of liquid and prove that γr = γg + γa where
the symbols have their usual meanings.
4) Define
linear and cubical expansivities of solids. Derive an expression for the
variation in density of solid when its temperature is raised from ϴ1oC
to ϴ2 oC.
5) How
do you determine the coefficeint of linear expansion of solid by Pullinger's
method? Can same method be used to find the coeffeicnt of superficial expansion
of same solid?
Numerical
1) A
rod is measured to be 20.05 cm long using a steel ruler at a room temperature
of 20oc both the rod and the ruler are placed in an oven at 270 oc,
where the rod now measures 20.11cm using the same ruler. Calculate the
coefficient of thermal expansion for the material of which the rod is made. (α
for steel = 11×10-6/oc).
2) A
steel tire of internal diameter 0.998m at 15oc is to be fitted on a
wheel of diameter 1.00 m. To what temperature must the tire be heated before it
can be slipped on? Linear expansivity of steel 12×10-6 /oc
3) An
aluminium vessel of capacity 300cc is completely filled with glycerin at 250C.
What volume of glycerin will overflow when the system is heated to 1150C?
(Volume expansivity of aluminium is 76.5x10–6/0C and that
of glycerin is 5.3x10–4/0C)
4) A
glass vessel of volume 50 cm³ is filled with mercury and is heated from 20˚C to
60˚C. What volume of mercury will overflow?(αg=1.8x10ˉ⁶/˚C and γHg=1.8x10-4/˚C)
5) A
silica bulb of negligible expansivity hold 340 gram of mercury at 0oC
when fall. Some steel balls are introduced and remaining space is occupied
at 0oC by 255 gram of mercury. On heating the bulb and
it’s contents to 100oC, 4.8 gram of mercury overflow. Find the
linear expansivity of the steel. ( cubical expansivity of mercury = 180 ×10-6/k)
6) Brass
rod of length 0.40m and steel rod of length 0.60m, both are initially at 0.0C
are heated to 750C. If the increase in lengths is the same for both
the rods, calculate the linear expansivity of brass. The linear expansivity of
steel is 12x10–60C–1.
7) A
steel cylinder has an aluminium alloy piston and is at a temperature of 200C
when the internal diameter of the cylinder is exactly 10cm. There is an all
round clearance of 0.05mm between the piston and cylinder wall. At what
temperature will the fit be perfect? (The linear expansivity of steel and
aluminium alloy are 1.2x10–5k–1 and 1.6x10–5K–1respectively)
8) A
clock which has a brass pendulum beats seconds correctly when the temperature
of the room is 300C. How many seconds will it gain or lose per day
when the temperature of the room falls to 100C? (for brass α=
0.0000180C–1)
9) A
pendulum clock gains 5sec at 150C and looses 10sec at 300C.
Find the value of coefficient of linear expansion.
10) A metal
rod 30cm long expands by 0.075cm when its temperature is raised from 00C
to 1000C. A rod of different metal and of the same length expands by
0.045cm for the same rise in temperature. A third rod, also 30cm long, is
made up of pieces each of the above metals placed end to end, and expands
0.065cm between 00C and 1000C. Find the length of each
portion of the composite bar.
11) An
aluminum rod when measured with a steel scale, both being at 250C
appears 1m long. If the scale is correct at 00C, what is the true
length of rod 250C? what will be the length of rod at 00C)
(αal= 26x10–6/0C and γsteel= 36x10–6/0C)
12) Using
the following data, determine the temperature at which a wood will just sink in
benzene:
Density of benzene at
00 C (ρb0) = 9.0 x 102kg m–3
Density of wood at 00 C
(ρw0) = 88 x 102kg m–3
Cubical expansivity of
benzene (γb0) = 1.2 x 103K–1
Cubical expansivity of
wood (γw) = 1.5 x 10–4 /k
OPTICS
Short questions
1. Difference
between real image and virtual image.
2. Difference
between regular and irregular reflection.
3. Uses
of plane mirror, concave mirror and convex mirror.
4. Characteristic
of image formed by plane mirror.
5. Can
a plane mirror ever forms real image?
6. Difference
between virtual image formed by plane mirror, concave mirror and convex mirror.
7. Which
mirror is used as a shaving mirror why?
8. Why
are convex mirrors used in cars for rear view?
9. A
ray of light is normally incident on a plane mirror, what are the values of
glancing angle and angle of deviation?
10. What
type of mirror is used in search light?
11. An ant
is approaching a concave mirror with a uniform speed up to focus. How would the
speed of image of an ant formed by lens change?
12. What is
the focal length of plane mirror? Does the mirror formula hold good for a plane
mirror?
13. A
spherical mirror is immersed in water; does its focal length change?
14. If you
are bringing a plane mirror towards your face at the speed of 10 m/s . at what
rate the image is approaching?
15. When is
formation of real image possible in a convex mirror?
16. What is
focus? What is the difference between focus and principal focus?
17. Prove
that the minimum size of plane mirror for a person to see his full image is
equal to half of his height.
18. Trace
the path of rays to locate the image when an object is brought from infinity to
pole of a concave mirror.
19. Two
plane mirrors inclined to each other at an angle 70o. . A ray
is incident on one mirror at angle α. The ray reflected from this mirror falls
on the second mirror from where it is reflected parallel to the first mirror.
Determine the value of α.
20. Define: a)luminous
flux b) luminous intensity c)iluminance d) lumen e)candela f) inverse square
law g) lux
21. Why does the illuminance of a
surface decrease as it moved away from the light source?
22. What is the meaning of
Luminous intensity?
23. Define luminous flux. State
its unit of measurement.
24.What are the factors on which
the illuminance of a surface depends?
25. Define luminous efficiency of
a source of light and give its SI unit.
26. What is the difference between
lumen and lux?
27. Define illuminance. Name the
factor upon which it depends.
28. The sun is less bright in
morning and in evening as compared to that at noon although its distance from
the observer is almost the same. Why?
29. Distinguish between
illuminance and luminance.
Long questions
1) State
and explain the law of reflection of light and rotation of light.
2) Define
focal length and radios of curvature of spherical mirror. How are they related
to each other?
3) Define
center of curvature. Obtain an expression for mirror formula of concave mirror
in the case of virtual image.
4) Obtain
mirror formula for concave mirror.
5) Define
principal focus. Derive the formula 
1/u+1/v
=1/f 
for the convex mirror.
1/u+1/v =1/f for the convex mirror.
Numerical
1) An
object 10cm high is placed in front of a convex mirror of focal length 20cm and
the object is 30cm fro the mirror. Find the height of the image.
2) A
2cm tall object is placed at 25cm from a concave mirror of focal length 20cm.
Find the position, size and nature of the
3) An
erect image, three times the size of the object is obtained with a concave
mirror of radius of curvature 36cm. What is the position of the object?
4) A
concave mirror forms a real image four times as tall as the object placed 10cm
in front of mirror. Find the position of the image and radius of curvature of
the mirror.
5) It
is desired to cast the image of lamp magnified 4 times upon a wall to 40 cm
distance from the lamp. What type of spherical mirror is used what is its
position?
6) A
mirror forms an erect image 30 cm from the object and twice its height. Where
must be the mirror situated. What is the radius of curvature, assuming the
object real determine whether the mirror concave or convex?
7) A
convex mirror of radius of curvature 20 cm forms an image which is half the
size of object. Locate the position of the object and image..
8) An
object is situated 40 cm from the convex mirror. When a plane mirror is
inserted between object and convex mirror at distance of 32 cm from the object.
The image of two mirror coccids. What is the focal length of convex mirror?
9) A
concave mirror forms, on a screen, an image of twice the linear dimensions of
the object. Object and screen are then moved until the image is three times the
size of object. If the shift of the screen is 20cm, determine the shift of the
object and focal length of the mirror?
10) With a
convex mirror, when the object is kept at a distance of 30 cm from the
mirror, the image is formed at a distance of 10cm from the mirror. What
will be the change in the image distance if the object distance is doubled?
11) A meter
scale is placed along the axis of a convex mirror of local length 25cm, its
nearer end being at a distance of 50cm. calculate the size of the image formed.
12) A pole
4m long is laid along the principle axis of a convex mirror of focal length 1m.
The end of the pole nearer the mirror is 2m from it. Find the length of the
image of the pole.
13) A small
object placed in front of a spherical mirror gives an image that is real and 4
times the size of object. When the object is moved 10cm towards the mirror a
virtual image of the same magnification is formed. Find the focal length of the
mirror.
14) A
convex mirror with a radius of curvature 30cm, forms real image 20cm from its
pole. Explain how it is possible and find whether the image is erect or
inverted.
ELECTROSTATICS
Short questions
1) What
do you mean by electric charge? Explain the basic properties of charge.
2) What
do you mean electrification? Explain various method of charging body.
3) How
many electrons are combined in 1 coulomb of charge?
4) Calculate
the charge carried by 20×1018 electrons.
5) Charge
of 4.8×10-15 C is transformed from the plastic ruler to silk.
How many electrons are transformed in this process?
6) What
is the total charge of 1Kg electron?
7) A
metallic chain is dragged on the ground from a vehicle that carries inflammable
materials, why?
8) Why
does a photograph record dust particles just after it is cleaned?
9) Electric
potential of earth is taken to be zero, why?
10) Why is
it dangerous to take shelter under a tree during lightning?
11) Can two
electric lines of force ever intersect each other? Explain.
12) Can a
conductor be given limitless charge?
13) If an
isolated metal sphere is given a positive charge, what would happen to its
mass?
14) If an
isolated metal sphere is given a negative charge, what would happen to its
mass?
15) Why do
you sometimes experience a slight electric shock when getting out of your car?
16) Electrostatic
experiments do not work well in humid days. Explain
Long Questions
1) What
do you mean by electrostatic induction? How would you charge a body negatively
by induction?
2) What
do you mean by electrostatic induction? How would you charge a body positively
by induction?
3) What
are the properties of charge?
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