Physics Classes

Category: Assignments

  • Important questions of oscillations

    Important questions of oscillations-

    1. What is meant by periodic and oscillatory motion? Distinguish between them.

    2. What is meant by SHM . Find the expressions for displacement , velocity and acceleration. Also find the phase difference between them.

    3. Find the potential energy and kinetic energy of a SHM and hence show that total energy is conserved . In what position of the oscillation is the energy wholly kinetic and wholly potential?

    4. Prove that for an harmonic motion time period T = 1/2π(spring factor/inertial factor)1/2.

    5. What is simple pendulum? Derive expression for the time period or frequency of the oscillating simple pendulum. Also explain the second pendulum and find the length of the second pendulum on the surface of earth.

    TO GET THE IMPORTANT QUESTIONS OF MECHANICAL PROPERTIES OF FLUID CLICK HERE-

    6. Show that vibration of the liquid in the U-Tube is simple harmonic and also find the expression for the time period and frequency .

    7. Explain the term (i) Free vibration (ii) Forced vibration (c) Resonant vibration (d) Damped oscillation.

    8. A cylinder floating in water is temporarily pushed down . Derive an expression for its frequency.

    9. Obtain an expression for the time period of a loaded and massless spring (i) Oscillating horizontally (ii) oscillating vertically . Show that is the same as the simple pendulum of length equal to the extension of the spring?

    Numericals-

    1. A body describe S.H.M. with am amplitude of 5cm . and a period of 0.2sec . Find the acceleration and velocity  of the body when the displacement is (a) 5cm (b)3cm (c)0cm.

    2.  Simple pendulum of length l and having a bob of mass m is suspended in a car . The car is moving on a circular path of radius R with a uniform speed v . If the pendulum makes small oscillation in a redial direction about its equilibrium position . What will be its time period?  

    3. A spring balance has a scale that reads from 0 to 50 kg . the length of the scale is 20cm. A body suspended from this balance when displaced and released , oscillation with a period of 0.60 sec. What is the weight of the body?                                            Ans-219N

    4. The acceleration due to gravity on the surface of the moon is 1.7m/s2. What is the time period of the simple pendulum on the moon if its time period on the surface of the earth is 3.5sec?     Ans-8.4 sec

    5. A spring with spring constant 1200N /m is mounted on the horizontal frictionless table , a mass of three kg it attached to the free end of the spring . The mass is then pulled sideway to a distance of 2cm and released . Determine (a) the frequency of oscillation (b)the maximum acceleration of the mass (c) The maximum speed of the mass.          Ans- 3.2 ; 8.1 ; 0.4

    To get the very important questions of Thermodynamics click here-

  • Important questions of mechanical properties of fluid in rest

    Important questions of mechanical properties of fluid in rest (Hydrostatics);

    This assignment contain all important questions based on the topic , liquid pressure, Pascal’s law, surface tension etc. It will help the students to prepare for the schools examination for class 11th.

    1. Define thrust  and derive an expression for the pressure at depth in a liquid at rest under gravity.

    2. State and prove Pascal’s law . Describe the principle and working of hydraulic press, or hydraulic lift.

    3. What do you mean by up-thrust force? explain.  Obtain the conditions for floating and equilibrium of a floating body.

    4. Describe briefly Torricelli’s experiment. What do you understand by the statement that the atmospheric pressure in 76cm of Hg column.

    5. Define surface tension and surface energy show that surface energy is equivalent to surface tension.

    6. Define angle of contact . How can it be determined  in case of mercury and glass?

    7. Derive an expression for the excess pressure inside (i) a liquid drop and (ii) a soap bubble (iii) an air bubble in liquid .

    To watch the video on the topic excess pressure inside liquid drop and soap bubble click here-

    8. What is capillarity? Explain the capillary rise in liquid , deduce an expression for the rise .

    9. Explain why

    (a) The angle of contact of mercury with glass is obtuse , while that of water with glass is acute.

    (b) Water on a clean glass surface tends to spread out while mercury on the same surface tends to form drops .

    (c) Surface tension of a liquid is independent of the area of the surface .

    (d)Water with detergent is dissolved in it should have small angles of contact .

    (e) A drop of liquid under no external force is always spherical in shape .

    (f) To keep a piece of paper horizontal. You should blow over not under it.

    (g)A spinning cricket ball in air doesn’t follow a parabolic trajectory.

    Numericals-

    1. A 50 kg girls wearing high heel shoes balance on a single heel . The heel is circular with a diameter 1.0cm . What is the pressure exerted by the heel on the horizontal floor?    Ans-6.2x 106N/m2.

    2. What is the pressure inside the drop of mercury of radius 3mm at room temperature? T for mercury is 4.56×10-1n/m also give the excess pressure inside the drop. Ans-310pa,1,01×105N/m2.

    3. A U-shaped wire is dipped in the soap solution, and removed . The thin soap film formed between the wire and the light slider support a weight of 1.5×10-2N . The length of the slider is 30cm. What is the surface tension of the film?     Ans-2.5×10-2N/m.

  • Very important questions of thermodynamics

    Important questions of thermodynamics-

    1. What is the zeroth law of thermodynamics ? How does it lead us to the concept of temperature?

    2. Define isothermal and adiabatic process . What are the conditions necessary for such process to occur?

    3. State and explain the first law of thermodynamics. Also write its limitations.

    4. Define two principle specific heat of gas . Why is Cp greater then Cv ?

    5. Define two specific heat of a gas and show that the difference between them is constant . (or, Derive Mayer’s formula).

    6. Describe melting and boiling process on the basis of first law of thermodynamics.

    7. Show that for an adiabatic change in a perfect gas PVƳ=constant, where P is pressure and V is the volume and Ƴ is the ratio of two specific heat of the gas.

    8. Define isothermal change . Calculate the amount of work done when perfect gas expand isothermally.

    9. Define adiabatic change . Calculate the amount of work done when perfect expands adiabatically.

    10.  Derive a relation between the slopes of an isothermal and adiabatic curve.

    11. State second law of thermodynamics in the two usual forms. Show that both these forms are equivalent to each other. Also write the limitations of second law of thermodynamics.

    12. What is the heat engine ? Explain the basic principle with the help of a flow diagram. Also explain its efficiency .

    13. What is a Carnot cycle? Find its efficiency. Does this efficiency depends on the working fluid ?Does any actual engine reach to the efficiency of Carnot engine ? Give reason  .

    Numericals-

    1. A cylinder with a movable piston contains 3 mole of hydrogen at standard temperature and pressure. The wall of the cylinder is made of insulating . By what factor does the pressure of the gas increase if the gas is compressed to half of its initial value?    Ans-21.4

    2. In changing the states of a gas adiabatically from an equilibrium states A to another Equilibrium state B , an amount of work equal to 22.3J is done on the system . If the gas is taken from state A to B via process in which the net heat absorbed by the system is 9.35 cal, how much is the net work done by the system in latter case ?               Ans-16.9 J

    3. A steam engine delivers 5.4×108J of work per minute. What is the efficiency of the engine ? How much heat is wasted per minute?                        Ans- 15%, 3.06x10J .

    4. An electric heater supplies heat to a system at a rate of 100W . The system prefer work at the rate of 75J/sec. At what rate the internal energy increasing?                  Ans-25 watt.

    5. A thermodynamic system is taken from an original states D to an intermediate state E by the liner process shown in fig,

    Its volume is then reduced to the original value From E to F by an isobaric process . Calculate the total work done by the gas from D to E to F.

  • Short answer type questions of ray optics

    Short answer type questions- (2 marks),

    This assignment provides Very important short answer type questions of ray optics which is very important for the class 12th board examinations.

    1.What are the necessary conditions for the phenomenon of total internal reflection to occur . Also write the relation between refractive index and critical angle for a given pair of optical media.

    2. State the principle on which the working of an optical fiber is based. What are the necessary conditions of  phenomenon to occur?

    3. Define critical angle . Obtain a relation between refractive index and critical angle for a pair of media . Does critical angle depends on the colour of light ? Explain.

    4. Draw ray diagrams to show how specially designed prism make use of total internal reflection to obtain the inverted image of the object by deviating rays (i) through 900 (ii) through 1800.

    5. Find the relation between real depth and apparent depth with the refractive index , when light moves from denser medium to rarer medium.

    6. A fish in the water tank sees the outside world as if fish at the vertex of cone such that the circular base of the cone coincide with the surface of water . Given the depth of water were fish is located being h and critical angle for water-air interface being ic , find out by drawing the ray diagram the relationship between the radius of the cone and height h.

    7. Draw the ray diagram showing the path of a ray of light entering through a triangular glass prism . Deduce the expression for the refractive index of glass prism in terms of the angle of minimum deviation and angle of the prism.

    8. A convex lens of focal length f1 is kept in contact with another lens of focal length f2 . Find an expression for the focal length of the combination.

    Watch the video of related topic combination of lenses click here-

    9. Why does the sun appear reddish at sunset or sunrise? For which colour the refractive index of prism material is maximum and minimum?

    10. Draw the ray diagram showing formation of image by a magnifying glass when the image is formed at infinity also find the angular magnification of image.

    11. Define the magnifying power of compound microscope when the final image is formed at infinity. Why does objective and the eyepiece of a compound microscope has short focal lengths ? explain.

    12. Draw  a schematic diagram of reflecting telescope (Cassegrain). Write its two advantages .or, Modern telescope prefer using suitable mirrors over using suitable lens , give two reasons for this preferences.

    13. Use a lens formula and show that (i) Object placed at the focal length of the convex lens for image at infinity.(ii) Object is placed between O(optical center) and F (focus) the image will be virtual.

    14. Draw a plot showing the variation of power of a lens with the wavelength of the incident light.

    15 A double convex lens made from a material of refractive index µ1 is immersed in liquid of refractive index µ2 where µ2>µ1 . What change if any, would occur in the nature of the lens?

  • Important questions of thermal properties of matter

    Important questions of thermal properties of matter

    This assignment provides all important questions of this chapter , which will be important for examinations point of view.

    1. Briefly describe the various scale of temperature and give the relation between them.

    2.Define coefficient of linear ,area and volume expansion , also find the relation between them.

    3.Show with the help of potential energy diagram that thermal expansion in solid is due to increase in interatomic distance.

    4. What do you mean by the term thermal stress? Derive an expression for the same in case of a road fixed at both ends.

    5. Define heat capacity, molar heat capacity and specific heat capacity also give their units and dimensions.

    6. What do you mean by the term latent heat of fusion and latent heat of vaporization ?

    7.Using P-T diagram of water , discuss the behavior of water when both pressure and temperature are (i) above the triple point (ii) at triple point (iii)below the triple point.

    8. What is thermal conduction ? Discuss the variable and steady state of a rod being heated at one of its ends.

    9. Define the coefficient of thermal conductivity and explain the formula used . Why do metals have higher conductivity then insulator?

    10. Write the expression for the rate of flow of heat energy through a conductor maintained at different temperature at its two ends . Explain the symbols used . Given that heat is measured in joule , derive the units of thermal conductivity.

    11.What is Newton’s law of cooling / how can it be experimentally verified? Plot the graph of log (T-T0) V/S time ‘t’.

    12.Discuss energy distribution in the spectrum of perfectly black body. What conclusion do you derive from this distribution? Also explain the Wine’s displacement law of radiation.

    13. State and explain Stefan’s law . How will you deduce  Newton’s law of cooling from this law?

    14. State and prove Kirchhoff’s law of heat radiation . Explain how Kirchhoff’s law leads to the conclusion that good absorber are good emitters.

    Numericals-

    1. A surveyor uses a steel measuring tape that is exactly 50m long at a temperature of 200C . What is the length on the hot summer day when the temperature is 350C?                                                              coefficient of linear expansion is  1.2 x 10-5K-1. .   [ans-50.009m]

    2. A glass flask with volume 200cm3 is filled to the brim with mercury at 200C . How much mercury overflows when temperature of the system is raised to 1000C ?[α for glass is 0.40x 10-5K-1.and cubical exp. For mercury is 1.2x 10-5K] . Ans-2.7cm3].

    3. A pendulum clock consist of an iron rod connected to a small heavy bob. If it is designed to keep correct time at 200C, how fast or slow will it go in 24 hours at 400C. ( α for iron is 1.2×10-5K-1).                Ans-10.4 sec

    4.At what temperature is the Fahrenheit scale reading equal to(I) half that on the Celsius scale (II)Equal to the reading on Celsius scale?

    5.A faulty thermometer reads 50C in melting ice and 990C in steam . Find the correct temperature in 0F when this faulty thermometer reads 520C.

    6.

    An iron bar of length l1=0.1m, A1=0.02m2, k1= 79w/mK and a brass bar of length l2=0.1m area 0.02m2 and K2=109 W/mK are soldered end to end as shown in fig. the free ends of the iron ball and brass bar maintained at 373K and 273K respectively . Obtain expression for and hence compute (a) the temperature of the junction(b) the equivalent thermal conductivity of the compound bar and (c)the heat current through the compound bar.   Ans-315K ,91.6W/mK, 916W.

    7. A body cools from 700c to 500C in 6 minutes and to 400C in 12 minutes . Find the temperature of the surroundings if cooling occur according to Newton’s law of cooling.        Ans-300C.

    8. A pan filled with hot food cools from 940C to 860C in 2 minutes when the room temperature is 200C . How long will it take to cool from 710C to 690c .    Ans- 42sec.

    9. The energy emitted per second by a black body at 12270C is E . If the temperature of the black body is increased to 27270C , calculate the energy emitted per second in terms of E in the second case. Ans-16E

    10. Calculate the temperature in kelvin scale at which a perfectly black body radiates at the rate of 5.67 W/cm2. Given σ=5.67×10-8W/m2K4.                                  Ans-1000K.

  • Numericals based on expansion of matter

    Before to solve these questions students must studied the topic Thermal expansion of matter , to watch the complete notes on this topic click here 

    Important numericals based on expansion of matter-

    1. A surveyor uses a steel measuring tape that is exactly 50m long at a temperature of 200C . What is the length on the hot summer day when the temperature is 350C?                                                              coefficient of linear expansion is  1.2 x 10-5K-1. .   [ans-50.009m]

    2. A glass flask with volume 200cm3 is filled to the brim with mercury at 200C . How much mercury overflows when temperature of the system is raised to 1000C ?[α for glass is 0.40x 10-5K-1.and cubical exp. For mercury is 1.2x 10-5K] . Ans-2.7cm3].

    3. A pendulum clock consist of an iron rod connected to a small heavy bob. If it is designed to keep correct time at 200C, how fast or slow will it go in 24 hours at 400C. ( α for iron is 1.2×10-5K-1).                Ans-10.4 sec

    4. When a strip made of iron (α1) and copper (α2)(α2>α1)is heated then (a)Its length doesn’t change (b)It gets twisted (c)It bends with iron on concave side (d) it bends with iron on convex side.   Ans-c

    5. The volume coefficient of expansion of a liquid is 7 times the volume coefficient of expansion of the vessel. The ratio of absolute and apparent expansion of the liquid is (a) 1/7 (b)7/6 (c)6/7(d)1/6.ans-b

    6. The coefficient of areal expansion of a solid is 2x 10-5 0C-1. Calculate the coefficient of linear expansion.

    7. A bar of iron is 10cm at 200C. At 190Cit will be ( α=11 x10 -5/0C). (a) 11 x10 -6cm longer (b) 11 x10 -6cm shorter (c) 11 x10 -5cm shorter (d) 11 x10 -5cm longer. Ans-c

    8. Coefficient  of volume expansion of mercury is 0.18×10-3/0C. If the density of mercury is 13.6 gm/cc . Then its density at 2000C is (a) 13.11g/cc (b)52.11g/cc (c)16.11g/cc (d) 26.11g/cc. Ans-a

    9. A meter rod of silver at 00C is heated to 1000C Its length is increased by 0.19 cm then the coefficient of volume expansion of the rod is (a) 5.7 x10 -5 /C (b) 0.63 x10 -5/C   (c) 1.9 x 10-5/C (d) 16.1 x10 -5/C . Ans-a

    10. Ratio among coefficient of  linear exp. , area and volume exp. Is (a)1:2:3 (b)3:2:1(c)4:3:2 (d) all of these . Ans-a

    11. A solid ball of metal has a concentric spherical cavity within it . If the ball is heated , the volume of the cavity will (a( increase (b) decrease (c) remain same(d) all are possible. Ans-a

    12. Solid expands on heating because (a) Kinetic energy of the atom increases(b)potential energy of the atom increases (c) total energy of atom increases (d) The potential energy curve is assymetric about the equilibrium distance between neighbouring atoms. Ans-d

  • Important numericals on temperature and thermometer (Temperature scale)

    Temperature is a relative measure of hotness or coldness of a body. An object at a higher temperature is said to be hotter than the one at a lower temperature. The S.I. unit of temperature is Kelvin(K).

    (We must keep it in our mind that , Heat and temperature are not the same thing , heat is the flow of energy , whereas temperature is a microscopic property of body.)

    Important numericals on Thermal properties of matter.

    A- Numericals based on temperature and( temperature scale)

    Formula used in the following questions-

        [ ( Tc-0)/100 = (tF-32)/180 = (tK-273)/100 = (tr-F.P.)/(B.P. –F.P.) ]

    temperature scales

    1. An object has a temperature of 500F. What is the temperature in degrees Celsius and in Kelvin?

     [Ans- 100C, 283.15K]

    2. A pan of water is heated from 250C to 800C. What is the change in the temperature in Kelvin scale and on the Fahrenheit scale?   [Ans- 55K,990F]

    3. A faulty thermometers reads 50C in melting ice and 990C in steam .Find the correct temperature in 0F when this faulty thermometer reads 520C.    [Ans-1220F]

    4. At what temperature is the Fahrenheit scale reading equal to half that on the Celsius scale?             [Ans-0.6670F]

    5. At what temperature the reading on both Celsius and Fahrenheit scale remain the same? [Ans—400C]

    6. The triple points of neon and carbon dioxide are 24.57K and 216.55K respectively. Express temperatures on the Celsius and Fahrenheit scale. [Ans—248.580C, -56.60C, -415.440F,-69.880F].

    After solving these questions students have to learn- Thermal expansion, CLICK HERE-

    To solve the questions based on the thermal expansion-CLICK HERE

  • Important numericals of surface tension

    This assignment contains Important numericals of surface tension which is solved . solution is given just below the questions.

    1.The surface tension of the soap solution is 30 x 10-3N/m .How much work is done to increase the radius of the soap bubble from 1.5 cm to 3 cm .     Ans- 5.091 x 10-4 j.

    solution-

    2. A square glass plate of length 10cm and thickness 0.4cm, weighs 40 g in air . It is held vertically such that its lower edge rests on water surface. What is the apparent weight of glass plate now? (S.T. of water is 0.073 N/m).                                                     Ans-0.407N.

    3. The radii of two air bubbles are in the ratio 4:5 .Find the ratio of excess pressure inside them . Also compare the works done in Blowing these bubbles.             Ans-5/4  ; 16/25 .

    .

    4. A circular plate of radius 4cm and weight W is made to rest on the surface of water if a minimum pull of   W+F is required to clear the plate off the water surface then find F , given surface tension of water is 0.072N/M.                       Ans-0.018N .

    5. Water rises up in a glass capillary upto a height of 10cm , while mercury falls down by 3.5 cm in the same tube. If the angle of contact for water – glass and mercury-glass are is taken as 00 and 1350 respectively . compare the surface tension of water and mercury. [ density of water and mercury are 103 and 13.6×103kg/m3.].

    6. A canister has a small hole at its bottom .What penetrates into the canister when its base is at a depth of 40cm from the surface of water. If surface tension of water is 73.5 dyne/cm, find the radius of the hole .     Ans- 0.0375mm.

    To get the Important objective questions based on this topic click here–

  • Questions based on surface tension

    This assignment contains some important questions based on the surface tension, in which there are some objective and some numericals based questions.

    these questions are for the practice of the topic surface tension and surface energy, excess pressure inside the liquid drop, soap bubble , ascent formula etc.

    Question based on surface tension and surface energy

    Multiple choice questions. (Only one option is correct)

    1. The angle of contact doesn’t depend upon,     (a)  Temperature         (b)Surface impurity      (c) Cohesive force      (d) The inclination of surface in contact.   Ans -d

    2. When a capillary tube is immersed in a liquid , then the liquid of mass m rises in the capillary tube .If capillary tube of double radius is taken then the mass f same liquid rising in the tube is , ,     (a)   M/2        (b)   2M   (c) M/4     (d) 4M .                                                      Ans- b

    3. What will be the work done to increasing the radius of the soap bubble from r/2 to 2r . If surface tension of soap solution is T ? ,     (a) 3πr2T   (b) 30πr2T    (c)    9πr2T   (d) 12πr2T   . Ans-b

    4. pressure inside soap bubble are 1.02 atm and 1.05 atm respectively . then the ratio of their surface area is (a) 125/8 (b) 25/4  (c)5/2   (d)2/5.   Ans-b

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    5.The property utilized in the manufacture of lead shots is (a)specific gravity of lead   (b)specific weight of the liquid lead  (c) compressibility of the liquid lead  (d) surface tension of the liquid lead. Ans-d

    6. Two soap bubbles are connected by a tube as shown in figure , what happens when stopper s is removed ?

    (a)size of A increase   (b) size of B is decreased   (c) both takes the same size (d) size of bubble A decreases and size of bubble B increases.                     Ans-d

    7. Two soap bubble of radii 2cm and 4 cm are join to form a double bubble in air , then the radius of curvature of the interface is , (a)2√5 cm  (b)2cm  (c)4  cm (d)  2√3cm  .  Ans-c

    8. A square wire frame of  side l is floating on the surface of the liquid of surface tension T . The force required to pull out the frame from the liquid is  (a) Tl  (b) 2Tl  (c) 4Tl  (d) 8Tl . Ans-d

    9. Two drops of liquid coalesce to form a single drop . In this process energy is (a) Absorbed  (b) Evolved  (c) Either absorbed or evolved    (d) Neither absorbed nor evolved.  Ans-b

    10. Surface tension of a liquid , at critical temperature is (a)Maximum   (b)Unchanged  (c)  Zero (d) none of these.                                                                                                           Ans-c

    Important numericals based on this topic –

    TO WATCH THE VERY IMPORTANT TOPIC OF SURFACE TENSION WHICH IS EXCESS PRESUURE INSIDE THE SOAP BUBBLE AND LIQUD DROP CLICK ON THE VIDEO LINK GIVEN BELOW-

    1.The surface tension of the soap solution is 30 x 10-3N/m .How much work is done to increase the radius of the soap bubble from 1.5 cm to 3 cm .     Ans- 5.091 x 10-4 j.

    2. A square glass plate of length 10cm and thickness 0.4cm, weighs 40 g in air . It is held vertically such that its lower edge rests on water surface. What is the apparent weight of glass plate now? (S.T. of water is 0.073 N/m).                                                     Ans-0.407N.

    3. The radii of two air bubbles are in the ratio 4:5 .Find the ratio of excess pressure inside them . Also compare the works done in Blowing these bubbles.             Ans-5/4  ; 16/25 . .

    4. A circular plate of radius 4cm and weight W is made to rest on the surface of water if a minimum pull of   W+F is required to clear the plate off the water surface then find F , given surface tension of water is 0.072N/M.                       Ans-0.018N .

    5. Water rises up in a glass capillary upto a height of 10cm , while mercury falls down by 3.5 cm in the same tube. If the angle of contact for water – glass and mercury-glass are is taken as 00 and 1350 respectively . compare the surface tension of water and mercury. [ density of water and mercury are 103 and 13.6×103kg/m3.].

    6. A canister has a small hole at its bottom .What penetrates into the canister when its base is at a depth of 40cm from the surface of water. If surface tension of water is 73.5 dyne/cm, find the radius of the hole .     Ans- 0.0375mm.

    To get the solution of all numerical questions given above click here–

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  • Important objective questions of mechanical properties of fluid

    This assignment contains Important objective questions of mechanical properties of fluid , based on pressure atmospheric pressure , Pascal’s law , buoyancy etc.

    It will be beneficial for the students preparing for 11th , NEET / JEE and other examination.

    Mechanical properties of fluids

    Questions based on fluid pressure , atmospheric pressure, Pascal’s law

    1 . Dimension formula of pressure head is – (a) [M0 L0 T0 ]  (b) [M L-1 T-2 ] (c) [M0 L1 T-2 ] (d) [M0 L1 T0 ].

    Ans-d

    2.The two thigh bones each of cross-sectional area 10cm2 supports the upper part of the person of a mass 50 kg . The average pressure sustained by the bones is , (a) 2.5 x 105 N/m2 (b) 4 x 105 N/m2 (c) 5 x 105N/m2 (d) 106 N/m2 .

    Ans-a

    3.What is the pressure on the swimmer 20m below the surface of water? (a)1atm (b) 2atm (c) 3 atm (d) 4 atm  .

    Ans-c

    4. Water is filled to a height H behind the dame of width w . The resultant force on the dame is ( if d is  the density of water), (a) dgwH2  (b) 1/2 dgwH2 (c)2 dgwH2 (d)4 dgwH2.

    Ans-b

    5. A tank is filled by density d of liquid upto height H . The average pressure on the wall of the container is (a) dgH (b) ½ dgH (c) ¼ dgH (d) 1/8 dgH .

    Ans-b

    6. Increase  in pressure at one point of the enclosed liquid in equilibrium of rest is transmitted equally to all other point of the liquid . This is as per (a) Buoyancy  (b) Pascals law (c) conservation of momentum (d) Impulse .

    Ans-b

    7. By sucking through a straw , a boy can reduce the pressure in his lungs to 750mm of Hg ( density of Hg is 13.6 g/cm3). Using a straw he can drink water from a maximum depth of (a) 13.6 cm (b) 1.36 cm (d) 0.136 cm (d) 10 cm .

    Ans-a

    8. An open U-tube contains mercury , when 13.6 cm of water is poured  into one of the arms of the tube , then the mercury rise in the other arm from its initial level is (a) 1cm (b) 0.5 cm (c) 10cm (d) 5 cm .

    Ans-2

    9. A cylinder of radius R full of liquid of density d Is rotated about its axis at w rad/sec. The increase in pressure at the centre of the cylinder will be (a)     d w2 R2 /2                          (b)      d w2 R /2                        (c)      d2 w R /2             (d) d2 w2 R2 /2     .

    Ans-a

    10. A barometer kept in an elevator reads 76 cm  when the accelerator is accelerating upward . The most likely pressure inside the elevator is ( in cm of Hg ) (a) 74 (b) 75 (c) 76 (d) 77 .  Ans-d

    Questions based on Archimedes principle , Buoyancy (up-thrust )

    11. A body floating in water has 1/5th of its volume immersed in water . What fraction of its volume will be immersed , if it floats in liquid of specific gravity 1.2 ?                       ans- 1/6

    12. A cylinder of height 30 cm and radius 7cm is immersed completely in a fluid of density 1.3 x 103 kg/m3 . What is the buoyant force acting on it? G =10m/s2 .                    ans-60N.

    13. A metallic spheres weighs 35g in air  and 28.5 g in water. Find its relative density and also find its weight in a liquid of relative density 0.9 .                                               ans- r.d – 5.4 and app-wt-29.15g .

    14. A piece of gold weighs 50 g in air and 45g in water. If there is cavity inside the piece of gold , then find its volume ( density of gold is – 19.3 gm/cc) Ans-2.4

    15.An alloy of Zn and Cu weighs 16.8 g in air and 14.7 g in water. If relative density of Cu and Zn are 8.9 and 7.1 respectively then determine the  amount of Zn and Cu in alloy.  Ans- Cu-9.34 Zn-7.45g.

    16.An object of mass m is floating in a liquid of density x . if the object is made up of density y , then the apparent weight of the object in the liquid is (a) mg (b) mg(1-x/y) (c) mg (1-y/x) (d) zero. Ans-d

    17. A cube of edge length 10 cm is just balanced at the interface of two liquids A and B as shown in fig. if A and B has specific gravity of 0.6 and 0.4 respectively then the mass of the cube is .

    (a) 240g (b) 360g (c) 480g (d) 540g .   ans-c

    18.A boat having some iron pieces is floating in the pond , if iron pieces are  thrown in the pond then level of the liquid (a) increases (b) Decreases (c) may increase or decrease (d) remain the same. Ans-b

    19.When two liquid of same mass and different densities d1 and d2 mixed together, then the density of the mixture is (a) d1 +d2 (b) d1 +d2 /2 (c)  2d1 d2 / d1 +d2 (d) 2d1 +2d2 . Ans-c

    20. When two liquid of same volume and different densities d1 and d2 mixed together, then the density of the mixture is (a) d1 +d2 (b) d1 +d2 /2 (c) 2 d1 d2 / d1 +d2 (d) 2d1 +2d2 . Ans-a

    21. if there were no gravity, then which of the following will not be there for the fluid ? (a) viscosity (b)surface tension (c) pressure (d)  upward thrust . ans-d

    22. An ice cube contains a large air bubble . The cube is floating on the horizontal surface of water contained in a trough. What will happen to the water level when the cube is melts? (a) remain unchanged (b) it will fall (c) it will rise ( d) first it will fall and then rise . ans-a

    23. The density of ice is 0.9gm/cm3.What percentage by volume by volume of the block of ice will float outside the water. (a) 10% (b)45% (c)75% (d)90% . ans-a

    24. The reading of a spring balance when it is suspended in the air is 6oN . This reading is changed to 40N when it is submersed in water. The specific gravity of the block must be (a) 3 (b) 2 (c) 6 (d)1.5. ans-a

    25. The weight of a body in water is one third of its weight in air. The density of the body in gm/cm3 is (a) 0.5 (b) 1.5 (c) 2.5 (d) 3.5 .  ans-b