1. What isThe discovery of C.V Roman ?
A. C.V Roman Roman Contribution to physics is Roman effect. It deals with scattering of light by molecules of ,medium when they are existed to vibrational energy levels.
2.Distinguish Fundamental units and derived units?
A.Fundamental units are used measure fundamental quantities .Derived units are used to measure derived quantities .Fundamental units are independent.Derived units are obtained by the combination of fundamental units.
EX: Metre is fundamental unit of length ‘L’.metre/sec is derived unit of velocity Which is the combination of fundamental unit metre and second
3.It is necessary that a mass should be present at the centre of mass of any system?
A.No.It is not necessary to have some mass at centre of mass of the System.EX: In a ring or bangle centre of mass is its centre.There is no mass particle at centre of mass.
4.What happens to the coefficient of friction if the weight of the body is doubled?
A. When the weight of the body doubled still there is no change in coefficient of friction. Because frictional force directly proportional to normal reaction will also becomes doubled and coefficient of friction remains constant.
5.Why are spokes provided in a Cycle wheel?
A. The spokes of cycle wheel increase its moment of inertia. The greater the moment of inertia , the greater is the opposition to any change in uniform rotational motion.As a result the cycle run smoothener and stedier.If the cycle wheel had no spokes, the cycle would be driven in jerks and hence unsafe.
6.Why are drops and bubbles spherical ?
A. Due to Property of surface tension ,the surface of liquid behaves like a stretched membrane and has a tendency to acquire minimum surface area.The sphere has minimum surface area when compared to other shapes of same volume.Therefore,drops and bubbles acquire spherical shape in order to have the minimum surface area.
7.What is angle of Contact?
A.It is defined as the angle between the walls of the container and the tangent drawn over the surface of the liquid. This angle must be measured in the interior side of the liquid.
8.Define a absorptive power of a body.What is the absorptive power of perfect block body?
A.Absorptive power of a body defined as the ratio of energy absorbed by the body within the wave length range of λ and λ +dλ to the total energy flux following on the body.
Absorptive power,aλ = Energy flux absorbed in certain time / Total energy flux incident on the body in the same time
8.Define a absorptive power of a body.What is the absorptive power of perfect block body?
A.Absorptive power of a body defined as the ratio of energy absorbed by the body within the wave length range of λ and λ +dλ to the total energy flux following on the body.
Absorptive power,aλ = Energy flux absorbed in certain time / Total energy flux incident on the body in the same time
8.What are the lower
and upper fixing points in Celsius and Fahrenheit
scales?
A. Centigrade (Celsius) scale of temperature: In centigrade scale of temperature lower fixing point freezing point of water at one atmosphere pressure ,as 0⁰C. The upper limit is boiling point of water at 1 atm pressure,as 100⁰C.
Fahrenheit scale of temperature : In Fahrenheit sale , the lower fixed point is freezing point of water at one atmosphere pressure , as 32⁰F. The upper fixed point is boiling point of water ar 1 atm pressure , as 212⁰F.
A.Absorptive power of a body defined as the ratio of energy absorbed by the body within the wave length range of λ and λ +dλ to the total energy flux following on the body.
Absorptive power,aλ = Energy flux absorbed in certain time/ Total energy flux incident on the body in the same time
10. How can systematic errors can eliminated?
A.Systematic errors can be minimized by improving experimental techniques,selecting better instruments by taking mean value of number of readings and byu removing personal errors as far as possible
11.What is inertia ? What gives the measure of inertia?
A.The inability of a body to change its state by itself is known as inertia.
Inertia is of three types 1) Inertia of rest 2) Inertia of Motion 3)Inertia of direction
Mass of a body is measure for its inertia.
12.Ventilators are provided in rooms just below the roof why?
A. Density of hot air is less. So in a room hot air does to top layers i.e, nearer to the roof. When ventilators are provided nearer to the roof hot air will escapes easily from room .So we feel that the room is cool and circulation of air will become easy.
13.When does a real gas behave like an ideal gas?
A. No, real gas is perfect or ideal. At extremely low pressures and high temperatures, some real gases ( like H2,O2,N2,He etc) obey the gas laws to a fair degree of accuracy and hence, behave as nearly ideal gas.
15. If a diameter of a soap bubble is 10 mm and its surface tension is 0.04 N/m-1 `, find the excess pressure inside the bubble
A. Diameter of soap bubble = 10mm
Radius , r =5mm =5×10-3m
Surface tension , S=0.04N/m
Excess pressure inside the soap bubble p = 4S/r
P=4×0.04/5×10-3 =160/5 = 32Nm-2
16. State the Dalton’s law of partial pressures.
A. Dalton’s law of partial pressures: For mixture of non interacting ideal gases at same temperature and volume total pressure in the vessel is the sum of partial pressures of individual gases .
i.e, P=P1 +P2+………… where P is total pressure
P1 , P2,………….. etc are individual pressures of each gas.
14.What are the units and dimensions of a specific gas
constant?
A.For specific gas constant unit : Joule/Kelvin
Dimensional formula ; r= PV/T = ML2T-2K-1
.
15. If a diameter of a soap bubble is 10 mm and its surface tension is 0.04 N/m-1 `, find the excess pressure inside the bubble
A. Diameter of soap bubble = 10mm
Radius , r =5mm =5×10-3m
Surface tension , S=0.04N/m
Excess pressure inside the soap bubble p = 4S/r
P=4×0.04/5×10-3 =160/5 = 32Nm-2
16. State the Dalton’s law of partial pressures.
A. Dalton’s law of partial pressures: For mixture of non interacting ideal gases at same temperature and volume total pressure in the vessel is the sum of partial pressures of individual gases .
i.e, P=P1 +P2+………… where P is total pressure
P1 , P2,………….. etc are individual pressures of each gas.
17 . What is the contribution of S. Chandra Shekhar to physics?
A. S.Chandra Shekhar discovered the the structure and evolution of stars. He defined “Chandra Shekhar limit”which is used in the study of block holes.
18. Distinguish between accuracy and precision.
A. Accuracy : Accuracy indicates the closeness of a measurement to the true value of given quantity. If the measurement is nearer to true value then accuracy is more.
Precision: Precision of measuring instrument depends on the limit or resolution of the quantity measured with that instrument.
If the least measurable value is less, then precision is more for that instrument.
19. Why does a car with a flattened tyre stop sooner than the one with inflated tyres?
A. Due to flattening of tyres, frictional force increases. Because rolling friction force between the surfaces is proportional to area of contact. Area of contact increases for flattened tyres. So rolling frictional force increases and the car will be stopped quickly.
20. Define viscosity. what is the C.G.S unit for coefficient of viscosity?
A. Viscosity : The property of a fluid which opposes the relative motion between its layers is called Viscosity.
The C.G.S unit of Viscosity is poise.
21. State the zeroth law of thermodynamics?
A. Zeroth law of thermodynamics: It states that if two Systems say A&B are in thermal equilibrium with a third system ‘C’ separately then the two systems A and B are also in thermal equilibrium with each other.
22. Define molar specific heat capacity?
A. Molar specific heat capacity: It is defined as the amount of heat required to rise the temperature of one mole of a gas through 1⁰ C or 1K.
23.Give the example where the velocity of an object is zero but the acceleration is not zero .
A. For body thrown up vertically at maximum height its velocity v=0. But still acceleration due to gravity ‘g’ acts on it.
So even though velocity v=0, still then acceleration is not zero.
24. A horse has to pull harder during the start of the motion than later. Explain.
A. To start motion in a body we must apply force to overcome static friction ( Fs = µkmg). When motion is developed between the bodies then kinetic frictional force comes into account. Kinetic friction (Fs = µkmg) is always less than static friction. So it tough to start a body from rest than to keep it in motion.
25. By spinning eggs on a table top , how will ypou distinguish a hard boiled egg from a raw egg?
A. To distinguish between a hard boiled egg and a raw egg, we spin each on table top.The egg which spin at a slower rate shall be a raw egg. This is because in a raw eeg , liquid matter inside tries to reduce speed of rotation due to viscosity of liquids. Therefore, raw egg will spin with smaller angular acceleration.
26. How is average velocity different from instantaneous velocity?
A. Average velocity defined as the ration of total displacement to total time taken. It is independent of path of the body.
Average velocity = s2-s1 / t2-t1 .
Velocity of the particle at a particular instant of time is known as instantaneous velocity. Here time interval is very small.
Only in uniform motion, instantaneous velocity = average velocity. For all other cases instantaneous velocity may differ from average velocity.
27.What is green house effect ?
A. Earth will absorb heat radiation and reradiate heat energy of longer wave length. This longer wave length heat radiation is reflected back to earth to green house gases such as Corbondioxidev[O2], Methane [CH2], Chlorofluorocarbons, Ozone[O3]. As a result temperature of earths atmosphere is gradually increasing. This is known as green house effect.
28. What is latent heat of vaporization?
A. Latent heat of vaporization: It is defined as the amount of heat energy absorbed or rejected by unit mass of substance while converting from liquid to vapour to liquid state.
29. Write the Dimensional formulae for the following quantities.
1)Gravitational constant 2). Surfece Tension
A. 1) Gravitational constant = M-1L3T-2
2) Surfece Tension = MT-2
30. Distinguish between centre of mass and centre of gravity.
A.
Centre of mass
1. A point inside a body at which the whole mass is supposed to be concentrated. A force applied at this point produces translator motion.
2. Algebraic sum of moments of masses about centre of mass is zero.
3. Center of mass is used to study translator motion of a body when it is in complicated motion.
Centre of gravity
1)A point inside a body through which the weight of the body acts.
2) Algebraic sum of moments of weight about centre of gravity is zero.
3) Centre of gravity is used to know the stability of the body where it is to be supported.
31. What are the theoretical and practical limits of poisson’s ratio?
A. Theretiacal limits of poisson’s ratio = -1 to 0.5
Practical limits of poisson’s ratio 0 to 0.5
32. Find the excess pressure inside a liquid drop.
A. Excess pressure inside a liquid drop p = 2T/r
t = surface tension of liquid.
r= radius of liquid drop.
1)A point inside a body through which the weight of the body acts.
2) Algebraic sum of moments of weight about centre of gravity is zero.
3) Centre of gravity is used to know the stability of the body where it is to be supported.
31. What are the theoretical and practical limits of poisson’s ratio?
A. Theretiacal limits of poisson’s ratio = -1 to 0.5
Practical limits of poisson’s ratio 0 to 0.5
32. Find the excess pressure inside a liquid drop.
A. Excess pressure inside a liquid drop p = 2T/r
t = surface tension of liquid.
r= radius of liquid drop.
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