## Friction Experiment Viva Questions

**Coefficient of Friction Experiment Viva Questions and Answers**

*1. What is meant by friction? *

Friction is an opposing force that comes into effect when a body moves or even tries to moves over another body’s surface.

*2. Name the different types of friction. *

(i). Static friction, (ii) limiting friction and (iii) kinetic friction

## Frequency of AC Mains using Sonometer Viva Questions

**Frequency of AC Mains using Sonometer Experiment Viva Questions
with Answers**

*1 Which is more dangerous in use a.c. or d.c.? Why? *

Ans: For example, a 220V a.c has a peak value of 220 x √2 = 311 V whereas the peak value of a 220 d.c. is 220 V itself. Hence a.c. is more dangerous than d.c. of the same voltage.

## Newton's Law of Cooling Viva Questions

**Viva Questions on Newton's Law of Cooling Experiment**

*1. What is meant by internal energy? *

Ans: The sum of kinetic and potential energies of a body is called its internal energy.

*2. Define temperature. *

Ans: Temperature of a body is called as the degree of coldness or hotness of the body.

*3. State Newton's law of cooling*

Ans: The Newton's law of cooling is defined as the rate of decrease in heat from a body is directly proportional to the mean temperature difference between the body and its surroundings.

*4. What is meant by thermodynamics? *

Ans: Thermodynamics is a branch of science which deals with the study of transformation of heat energy into mechanical energy and vice-versa.

*5. What is absolute zero of temperature? *

Ans: —273.15° C

*6. What is the tripple point temperature of water?*

Ans: 273.16° K or 0.01°C

*7. Define isothermal process. *

Ans: Isothermal process is a physical change in which pressure and volume of a system change at constant temperature (It is a slow process).

*8. Define adiabatic process. *

Ans: Adiabatic process is a physical change in which pressure, volume and temperature change (It is a sudden process).

*9. What is meant by irreversible process? *

Ans: Any process that can't be retraced in the reverse order and in the opposite sense is called an irreversible process.

*10. What is meant by reversible process? *

Ans: A reversible process which can be made to proceed in two opposite directions with the same case, so that the system and the surroundings pass through exactly the same intermediate state as in the direct process.

*11. Name the different modes of transmission of heat.*

Ans: There are three modes of transmission of heat. They are conduction, radiation and convection.

*12. What is radiation?*

Ans: Radiation is energy or particles that origins from a source and travels through space or other medium. It may be able to go through various materials.

eg: Light, X-ray, Sound, Microwaves and so on

*13. What is Stefan-Boltzmann law?*

Ans: Stefan-Boltzmann law states that the total radiant heat power emitted from a surface is directly proportional to the fourth power of the black body’s absolute temperature.

ie, j* = σT^{4}

*14. Define emissivity (or relative emittance) of a surface.*

Ans: Emissivity (ε) is defined as the relative ability of a surface to emit heat by radiation. It is the ratio of radiant energy from an object’s surface at given temperature to the radiant energy of a black body at same temperature.

*15. State Kirchhoff's law.*

Ans: Kirchhoff's law of radiation states that at thermal equilibrium, the power radiated by an object is equal to the power absorbed by that object.

*16. What is the velocity of heat radiation?*

Ans: Thermal radiation or Heat radiation is the energy transfer in the form of electromagnetic waves. The velocity of thermal radiation in the vacuum is same as that of light.

c_{0} = n_{0}c

where, c_{0} = thermal radiation velocity

n_{0 }= refractive index of medium

c = wave velocity

*17. To which part of the electromagnetic spectrum do the
thermal radiation belong?*

Ans: Infrared region

*18. What is a black body?*

Ans: A black body is a surface that absorbs all radiant energy falls on it, regardless of frequency or angle of incidence.

*19. What is meant by black
body radiation?*

Ans: Blackbody radiation is defined as the spectrum of light emitted by any heated object. It is the radiation emitted by the black body. For example, filament of a light bulb

*20. What is Wien's displacement law?*

Ans: The wavelength at which the maximum radiated power for a blackbody is inversely proportional to the absolute temperature.

ie, λ_{max} = b/T

b = constant of proportionality

T = absolute temperature

*21. Aim of Newton’s law of Cooling*

Ans: To study the connection of temperature of a body to the time as it cools by radiating heat.

*22. Apparatus of Newton’s law of Cooling*

Ans: Calorimeter and stirrer, thermometer, clamp and stand, stop-watch, hot water and so on

*23. Principle of Newton’s law of Cooling*

Ans: By Newton's law of cooling, rate of cooling is directly proportional to mean temperature difference between the cooling substance (water) and the surrounding.

i.e., dθ/dt ∝ (θ-θ_{0})

where, θ - mean temperature of the cooling substance (water)

θ_{0} - temperature of the surrounding

As time increases, θ decreases, (θ-θ_{0}) decreases
and hence rate of fall of temperature dθ/dt also decreases.

*24. Procedure of Newton’s law of Cooling*

Ans: About 2/3 rd of the calorimeter is filled with hot water of
about 110°C. A thermometer is suspended inside the calorimeter from a clamp and
stand. Let θ_{0} be the temperature of the surrounding. Water is
stirred continuously to make it cool uniformly. When the temperature of hot
water falls to 100°C, a stop-watch is started. For every one minute the
temperature is noted. The time-temperature observation is continued till the
temperature falls to say 20°C.

A graph is plotted with time along the X-axis and temperature θ along the Y-axis, The graph is known as cooling-curve of the liquid.

## Young's Modulus Experiment Viva Questions

**Viva Questions on Young's Modulus Experiment**

*1. What is meant by stress? *

Ans: Stress is defined as the restoring force that is acting per unit area of a body.

*2. What is meant by strain? *

Ans: Strain is defined as the ratio of change in dimension to the original dimension.

*3. What is the unit of stress? *

Ans: Nm^{-2}

*4. What is the unit of strain? *

Ans: No unit.

*5. Define elasticity. *

Ans: The property of a body to recover its original pattern when the deforming forces are removed is called elasticity.

*6. Who was the first man to investigate the stretching of
metals? *

Ans: Robert Hooke

*7. State Hooke's law. *

Ans: Within the elastic limit, the stress grown is directly proportional to the strain created in a body.

*8. Which is more elastic either steel wire or rubber wire of
same diameters and lengths? *

Ans: Steel wire

*9. What is meant by Young's Modulus of elasticity? *

Ans: The ratio between the normal stress to the longitudinal strain in elastic limit is called as Young's modulus of elasticity.

*10. What is the unit of elastic limit? *

Ans: Nm^{-2}

*11. Distinguish between stress and pressure.*

Ans: The restoring force acting per unit area is Stress and the amount of force applied per unit area is Pressure.

*12. What is meant by elastic limit?*

Ans: The maximum stress for a body can withstand before the permanent deformation of size or shape.

*13. What is the modulus of elasticity?*

Ans: The relationship (ratio) between stress and strain is called as Modulus of Elasticity (Young's modulus of elasticity).

λ = stress/strain

*14. What are the different moduli of elasticity?*

Ans: (i) Young's modulus,

(ii) Shear modulus, and

(iii) Bulk modulus.

*15. What is the unit of modulus of elasticity?*

Ans: Nm^{-2} or Pa

*16. Why do you use a micrometer or vernier instead of a
metre scale to measure the increase in length of the wire?*

Ans: It is because the vernier can slide freely against the main scale.

*17. What is elastic hysteresis?*

Ans: Elastic Hysteresis is the difference between the strain energy and stress energy. It is the lagging of strain behind the stress.

*18. Aim of Young's Modulus Experiment*

Ans: To find out the Young's modulus of the material for a given wire by Searle's apparatus.

*19. Apparatus of Young's Modulus Experiment*

Ans: The Searl's apparatus, weight hanger, slotted weights, screw gauge, metre rule etc. The Searl's apparatus consists of two long metal wires AB and CD each of length about 2 m suspended side by side from a rigid support. AB is the experimental wire whose Young's modulus is to be determined. CD is the observation wire. The experimental wire AB carries a vernier V and the observation wire CD carries a main scale S. The vernier can slide freely against the main scale. The observation wire is made taut by suspending a load W at the lower end of the main scale.

*20. Procedure of Young's Modulus Experiment*

Ans: The experimental wire is made taut by placing a suitable dead load Wo on the weight hanger attached to the lower end of the vernier. It is brought into elastic mood by repeatedly loading, and unloading.

With the dead weight W_{0} alone, the reading r_{0}
of the vernier is taken. A suitable weight m, say 0.5 kg, is placed on the
weight hanger over the dead load and the reading of the vernier is again taken.
The experiment is repeated by adding load 2 m, 3 m, 4 m... over the dead load
and the vernier is read in each case. The load are removed one by one and the
vernier readings are again taken. The average readings r_{1}, r_{2},
r_{3}, r_{4},... for the load (W_{0} + m), (W_{0}
+2m) , (W_{0} +3m)(W_{0} +4m)…... are calculated. From these
readings extensions for the loads M = m, 2m, 3m, 4m, …. are taken as (r_{1}
— r_{0}), (r_{2} — r_{0}), (r_{3} — r_{0}),
(r_{4} — r_{0}),…. A
graph is drawn with extension along the Y-axis and load along the X-axis. The
graph is a straight line. The reciprocal of its slope gives M/l, the
load/extension of the wire.

The length L of the experimental were from the support to
the point of attachment to the vernier is measured by a metre rule. The radius
r of this wire is measured with a screw gauge. The Young's modulus of the
material of the wire AB is calculated by the equation. Y = MgL/πr^{2}l
= Lg/πr^{2} x (M/l)

## Atoms and Molecules Viva Questions

**ATOMS AND MOLECULES
VIVA QUESTIONS (CLASS 9)**

1. What is the Avogadro number of Helium (He) atoms weigh ?

**Ans: 4.0 g **

2.
Determine the number of hydrogen atoms in 3 mole of NH_{3} ?

**Ans: 9 x 6.02 x 10 ^{23}
**

3.
Which of the following weighs least among
the following?

(a)
0.224 litres of O_{2} at NTP

(b)
6.02 x 10^{23} molecules of oxygen

(c) 6.02 x 10^{23} atoms of carbon

(d)
10 g of CO2

**Ans: 0.224 litres of O _{2}
at NTP**

4.
An element's oxides contain 57.1 % and 72.1 % oxygen, respectively. What is the
second oxide if the first oxide is MO?

**Ans: MO _{2}**

5. What is the molarity of Na_{2}CO_{3}
solution containing 10.6 g per 500 ml solution?

**Ans: 0.2 **

6.
Determine the volume of 0.5 M HNO_{3} that can be prepared from 25 mL
of 2.5 M HNO_{3} ?

**Ans: 125 mL**

7.
If 30 L is converted into SI unit and expressed in scientific notation, determine the value obtained?

**Ans: 3 x 10 ^{-2} m^{3} **

8.
The average density of earth is 5.5 g cm^{-3}. In kg m^{-3}, determine
the average density?

**Ans: 5.5 x 10 ^{-3}
**

9.
In 1.0046, how many significant figures
are there?

**Ans: five **

10.
From the given lists, which of the following has more number of rnolecules ?

(a)
1 g CO_{2}

(b)
1 g N_{2}

(c)
1 g H_{2}

(d)
1 g CH_{4}

**Ans: 1 g H _{2}**

11.
Carbon monoxide and carbon dioxide may be taken as examples for illustrating which
law ?

**Ans: Law of multiple
proportions **

12.
From the given, which of the following contains Avogadro number of atoms,

(a)
11.2 L of H_{2} at STP

(b) 32 g of oxygen

(c)
28 g nitrogen

(d) 22.4 L of Cl_{2} at STP

**Ans: 11.2 L of H _{2}
at STP**

13.
Find the volume of oxygen at STP required to react with 3 g graphite to give CO_{2}
?

**Ans: 5.6 L**

14.
A solute has a molecular mass of 60 g and 90 g of it is dissolved in a litre of
solution. Then what is its molarity?

**Ans: 1.5**

15. From the given samples, determine which of
the following is not a mixture?

(a) air (b) milk (c) smoke (d) water

**Ans: Water**

16.
The volume of l g of a gas at STP is 1.12 L. What will be its molecular mass ?

**Ans: 20 **

17. A mass of 16 g of an element was mixed
with 32 g oxygen when 32 g of compound was formed. If the element was the
limiting reagent, what will be the mass ratio of the element to oxygen in the
compound ?

**Ans: 1:1 **

18.
Chemical equations are balanced so that they are in accordance with which law?

**Ans: Law of
conservation of mass **

19.
At NTP, 0.225 g of carbon reacts with 140 mL of oxygen. What would the
compound's molecular formula be then?

**Ans: C _{3}O_{2}
**

20.
0.25 g of a tetratomic element is 3.125 x 10^{-3} mole. Then what is the
atomic mass of the element is

**Ans: 20**

21.
Neon contains two isotopes of atomic masses 20 and 22 in the mass ratio 9 : 1 respectively. Find the atomic mass of the
element ?

**Ans: 20.2**

22.
What is the atomicity of ozone?

**Ans: The atomicity of
ozone is 2**

23. Determine which molecule from the
following elements is tetratomic?

(a) ozone (b) phosphorus (c) sulphur (d) xenon

**Ans: Phosphorus**

24.
What is the number of significant figures in 6.023 x 10^{23} ?

**Ans: The number of
significant figures is 4 **

25.
Determine the approximate number of atoms present in lg CH_{3}COOH ?

**Ans: The approximate number of atoms present is 10 ^{22
}**

26.
Find the number of significant figures in 0.0480 ?

**Ans: The number of
significant figures is 3**

27.
Give the number of dimensionally independent physical quantities in SI units?

**Ans: 7**

28.
Give the equivalent of 1 cm^{3} of volume?

**Ans: 10 ^{-3} dm^{3}**

29.
Determine the equivalent of one joule of energy ?

**Ans: 0.2381 cal **

30.
From the following, determine the SI unit of work?

(a) cal (b) Joule (c) litre-atm (d) ergs

**Ans: Joule**

31.
One kg weight is equivalent to

**Ans: 9.8 N **

32.
The unit of J. Pa^{-I} is equivalent to

**Ans: m ^{3} **

33.
From the listed elements, determine which
of the element is not an element?

(a) Diamond (b) 22 carat gold (c) graphite (d)
oxygen

**Ans: 22 carat gold**

34.
From the given mixtures, find which one
is not a homogeneous mixture?

(a)
one rupee coin (b) gasoline (c) iodised table salt (d) air

**Ans: Iodised table salt**

35.
Give the mass of a Mg atom ?

**Ans: The mass of Mg
atom is 24.3/6.02 x 10 ^{23} g **

36.
Determine the number of mols of carbon
present in 1 mot of ethanol?

**Ans: 2 **

37.
615.00 has...........significant figures

**Ans: 5**

38.
How will you measure the Luminous intensity ?

**Ans: The luminous
intensity is measured in terms of Candela **

39.
The prefix tera means

**Ans: 10 ^{12 }**

40.
Pure water can be obtained from sea water by which process?

**Ans: Distillation process**

41.
From the listed elements, find which one contains the largest number of
molecules?

(a)
1g CO_{2} (b) 1g N_{2} (c)
1 g H_{2} (d) 1 g CH_{4 }

**Ans: 1 g H _{2} **

42.
Carbon forms two oxides CO and CO_{2}. This illustrates which law?

**Ans: Law of Multiple proportions **

43.
Two oxides of a metal contain 50% and 60% of oxygen respectively. If the formula
of the first oxide is MO, determine the formula of the second one?

**Ans: The formula of the
second one is M _{2}O_{3} **

44.
What is the simplest formula for a compound with 50% of element X (atomic mass
10) and 50% of element Y (atomic mass 20) in it?

**Ans: The simplest
formula is: X _{2}Y**

45.
Which of the following contains the same number of atoms as in 6 g carbon?

(a)
24 g Mg (b) 23 g Sodium (c) 20 g Ca
(d) 63.5 g Cu

**Ans: 20 g Ca **

46.
3.2 g of gas contains 6.02 x 10^{22} molecules. determine its vapour
density?

**Ans: The vapour density
is 16**

47.
Find the volume of 1 M NaOH required to convert 1.2 g of NaHSO_{4}
completely to Na_{2}SO_{4} ?

**Ans: 10 ml**

48.
How many moles of water would be formed when 4 g of methane (CH_{4})
are burnt?

**Ans: 0.5**

49.
calculate the number of significant figures of the following numbers?

(a)
100.04

**Ans: 5**

(b)
4.20 x 10^{10}** **

**Ans: 3**

(c)
324.0

**Ans: 4**

(d)
500.00

**Ans: 5**

(e)
0.02670

**Ans: 4**

50.
Compute the following:

(a)
5.28 x 0.156 x 3/0.428

**Ans: 5.77**

(b)
5.28 x 0.156 x 3/0.421

**Ans: 5.67**

51.
List the proper number of significant
figures in the following and indicate which zeros are significant?

(a)
0.216

**Ans: 3 Significant
figures**

(b)
90.1

**Ans: 3 Significant
figures and zero is significant**

(c)
800.0

**Ans: 4 Significant
figures all zeros are significant**

(d)
0.0670

**Ans: 3 Significant
figures, last zero is significant**

52. Determine the number of moles of Oxygen atoms
are there in

(a)
one mole of HNO_{3}

**Ans: 3 moles**

(b)
one mole of H_{2}SO_{4 }

**Ans: 4 moles**

53.
Determine the number of moles of water produced when 8 g of methane (CH_{4})
are burnt?

**Ans: 1 mol.**

54.
How many moles of KClO_{3} are needed to give 1.5 moles of oxygen?

**Ans: 1 mol.**

55.
How many moles of KCl are formed when 0.33 mol of KClO_{3 }is
decomposed?

**Ans: 0.33 mol.**

56.
A chemist weighs 10 g of water, 10 g of ammonia and 10 g of hydrogen chloride.
Calculate the total number of moles contained in the mixture?

**Ans: 1.4 moles**

57.
Give the mass of a silver atom?

**Ans: 1.794 x 10 ^{-22}
**

58.
Determine the number of molecules contained in a drop of water weighing 0.04 g?

**Ans: 1.34 x 10 ^{21}
molecules**

59.
Express 0.000000367 in scientific notation and calculate the significant
figures?

**Ans: 3.67 x 10 ^{-7}
; Number of significant figures is 3**

60.
What is the mass of HCl required to neutralise completely 5g of NaOH?

**Ans: 4.545 g**

61.
Which contains more molecules: 1 g of sulphur dioxide or 1 g of sulphur
trioxide?

**Ans: 1 g of SO _{2}**

## Helical Spring Experiment Viva Questions

**Helical Spring Experiment Viva Questions and Answers**

*1. What is
the principle of a spring?*

Hooke's law

*2. Define
Hooke's law. *

According
to Hooke's law, within elastic limit, stress is directly proportional to
strain.

i.e., Stress/
Strain =a constant

*3. Define
strain. *

Strain = Change
in dimension /Original dimension

*4. Define
stress. *

It is the normal force acting per unit area

Stress = Restoring
force/Area

*5. What
will you do so that the load attached to the one end of the spring oscillates
in the vertical plane in order to obtain simple harmonic oscillations? *

Spring
should be suspended vertically and the amplitude of the oscillations should be
small.

*6. State
the condition under which a spring obeys Hooke's law. *

Extension
of the spring should remain within elastic limit.

*7. What are
the forces acting on the load that is attached to the spring which is
oscillating in a vertical plane? *

The forces
are weight and tension.

*8. Define
spring constant or force constant of a spring. *

F = -kx; where k is the spring constant. It is the
force required to produce unit extension on a spring.

*9. What is
the unit of force constant? *

newton /
metre (N/m)

*10. What are the conditions essential for the motion of a body to be simple harmonic?*

*11. What are the factors on which the period of vertical oscillations of a spring depend?*

*12. What is the unit of spring constant?*

^{-1}

*13. Which is more elastic-steel wire or rubber wire of the same diameter and length?*

*14. What is the spring constant in terms of load (M) and extension (e)*

^{-1}

*15. Aim of Experiment.*

To determine the spring constant by measuring the time period of vertical oscillations of a known load and to check the result by measuring the extension for a known force

*16. Apparatus
of Experiment.*

A helical
spring, Stand, Slotted weights, Stop-watch etc..

*17. Principle of Experiment.*

i. **Vertical
oscillations: **The period of vertical oscillations of a helical spring is given
by,

T = 2π√(M/K)

K = 4π^{2}(M/T^{2})

Where, K =
spring constant, M = Total mass attached, T = Period of oscillations

ii. **Load
extension method:** Using Hooke’s law, load is proportional to extension,

Spring
constsnt, K = Load/Extension = mg/l

*18. Procedure
of Vertical Oscillations of Experiment*

The given
spring is suspended from a rigid support. A weight hanger with a dead load (w_{0})
is suspended at the lower end of the spring (w_{0} should be sufficient
to bring the spring in the elastic mood). A pointer is attached to the spring.
The weight is slightly pulled down and released. The spring executes vertical
oscillations. The time taken for 20 oscillations is noted and the period of
oscillation (t/20) is calculated. Changing the loads [say (w_{0}+w), (w_{0}+2w),…..]
and the period of oscillations are again determined. In each case M/T_{2}
is calculated and hence its mean value is determined. A graph is plotted with M
along the X-axis and T_{2} along, the Y-axis. The graph is found to be
a straight line. From this K can also be calculated.

*19. Procedure
of Load-extension method of Experiment*

The given
spring is suspended from a rigid support. A pointer attached to the spring
moves over a scale. Reading on the scale for w0, (w_{0}+w), (w_{0}+2w)….
are found. The mean value of scale reading for loading and unloading are r_{0},
r_{1}, r_{2} ….. respectively. Extension (l) for loads w, 2w, 3w
…. Are given by (r_{1}-r_{0}), (r_{2}-r_{0}), (r_{3}-r_{0})
etc. are calculated. The spring constant,

K = Load/
Extension

A graph is
plotted with M along the X-axis and extension along the Y-axis. The graph is
found to be a straight line. From this K can also be calculated.