"Physics"

1.a)

What is gravitational force? What change will occur in gravitational force between two bodies if the distances increased keeping the masses constant? Mass of the earth is 6x 10²⁴ kg and radius of the earth is 6380 km. Calculate the weight of a man of mass 60 kg on the surface of the earth. (G=6x10⁻¹¹ Nm²/kg²)

The force of attraction between any two bodies due to their masses solely is called gravitational force.

If the distances is increased keeping the masses constant, gravitational force of the body will decrease by square of times the distance is increased.

Solution
Given
Mass of the earth, M_E = 6 x 10²⁴ kg
Mass of the man, M_m = 60 kg
Radius of the earth, R_E = 6380 Km = 6380,000 m = 6.38 x 10⁶ m.
Weight of man on the surface of earth is equal to the gravitational force between the earth and the man. This is given by,
Wₓ = G . M_E . M_m / R_E²
= [6x10⁻¹¹ . 6 x 10²⁴ .60 / (6.38 x 10⁶)²] N
= [ 2160 x 10⁻¹¹⁺²⁴/(40.7 x 10¹²) ] N
= 53.1 x 10⁺¹³⁻¹² N
= 531 N
Hence weight of man on the surface of earth is 531 N.

Acceleration due to gravity on the surface of earth, g = G . mₑ / r²
g = [ 6x10⁻¹¹ . 6 x 10²⁴ / (6.38 x 10⁶)²] m/s²
= 8.84 m/s²
Mass of the man, m =60 kg
Weight of the man, w = m.g = 60 x 8.84 N
= 530.65 N ≅ 531 N
Hence weight of man on the surface of earth is 531 N.



1.b)

What is alternative source of energy? Write two appropriate ways to replace fossil fuel in Nepal.

That source of energy which can be used instead of non-renewable source of energy is called alternative source of energy.

Some appropriate ways to replace fossil fuel in Nepal are as follows:-

(i) Nepal should harness its alternative energy potential.

(ii) Nationwide deployment of smart electric grid.

(iii) Replacement of petroleum driven industrial as well as personal machines by clean energy driven machines.

(iv) Biomass plant should installed in rural areas for cooking purpose.



2.a)

State Pascal's Law. A camel can walk easily on desert but a horse cannot, why? What will be the pressure exerted per square meter on it bottom when a water tank of 1 m each of length, width and height is completely filled with water?

Pascal's law states that if pressure is applied at a point in an enclosed vessel containing fluid then it is equally transmitted in all direction of that vessel.

A camel feet occupy more area than a horse feet hence less pressure is exerted by a camel weight on desert than a horse. That is why a camel can walk easily on desert but a horse cannot.

Length of the tank, L = 1m
Breadth of the tank, B = 1m
Height of the tank, H = 1m
Volume of the tank, V = L.B.H = 1m³
Density of water, d = 1000 kg/m³
Mass of water in the tank, m = V.d = 1,000 kg
Weight of the water, w = m.g = 1,000 x 10 N
= 10,000N
Area of bottom of the tank, A = 1 m²
Pressure exerted by water on the tank's bottom is given by
P = w/A
= 10,000/1 = 10,000 Pa
Hence pressure exerted by water on the tank's bottom is 10,000 Pa.



2.b)

Study the given diagram and answer the following questions. 

(i) Write the function of the instrument given in the diagram.

(ii) Which law is explained by the given instrument?

(iii) What weight of fresh water is displaced by the given instrument?

(i) The given instrument is used to measure specific gravity of liquid.

(ii) Archimedes's principle or law of buoyancy is explained by the given instrument.

(iii) 2N fresh water is displaced by the given instrument.



3.a)

Define specific heat capacity and write its SI unit. What is the specific heat capacity of a liquid if 2.2x10⁵ J of heat energy is required for 4 kg of liquid to raise its temperature from 35ºC to 60ºC?

Specific heat capacity of a body is defined as the amount of heat energy required to raise the temperature of 1 kg mass of the body by 1ºC.

Its S.I. unit is Jkg⁻¹ºC⁻¹ or Jkg⁻¹K⁻¹.

Heat required, Q = 2.2x10⁵ J
Mass of liquid, m = 4 kg
Initial temperature, T₀ = 35 ºC
Final temperature, T₁ = 60 ºC
Change in temperature, dT = T₁-T₀ = (60 - 35)ºC = 25ºC
Let "s" be the specific heat capacity of the liquid.
From heat equation
Q = m. s. dT
2.2x10⁵ J = 4 kg . s . 25ºC
2.2x10⁵ J = s . 100 kgºC
s = 2.2 x 10³Jkg⁻¹ºC⁻¹
∴ s = 2200 Jkg⁻¹ºC⁻¹
Hence the specific heat capacity of the liquid is calculated to be 2200 Jkg⁻¹ºC⁻¹.



3.b)

What is short sightedness? Mention its one cause. An object is placed between F and 2F of a convex lens, what type of image is formed? Draw raw ray diagram. Also write any two features of the image.

The defect of vision in which distant object is seen blurred while close objects are seen clearly is called short sightedness. It is also called myopia.

Video illustration ray diagram construction is as follows:-

Ray diagram for the above given question is as follows:-


Features of this image are as follows:-
(i) Real
(ii) Inverted.



4.a)

What is motor effect of current? Write two differences between step up and step down transformer.

Motor effect of current is the effect in which a current carrying conductor placed in a magnetic field, experiences a force.

Differences between step-up and step-down transformer are as follows:-






4.b)

What is voltmeter? From what metals coil of heater is made? What is the capacity of the fuse needed for a TV rated 220V and 80w? How many units of electricity is consumed if the TV is run for one month 4 hours daily?

Voltmeter is a device used to measure voltage drop between two points in an electric circuit.

Coils of heater is made from nichrome an alloy of nickel(Ni) and chromium(Cr).
Rated power of the TV, P = 80w
Rated voltage of the TV, V = 220V
Rated current of the TV, I = P/V = 80/220
=0.3636 A
The capacity of fuse should be 0.3636 ampere.

Time in hours for which TV runs everyday = 4 hrs
Number of days in a month = 30 days
time in hours for which the TV runs in a month, T = 30 x 4 hrs = 120 hrs
Energy consumed by TV in 1 month,
E = P x T
= 80 w x 120 hrs
= 9600 watt-hours
Energy consumed expressed in kWH
= 9600/1000 kWH
= 9.6 kWH

As we know 1 unit of electricity is equal to 1 kWH
So, the TV consumes 9.6 units in one month.





5.a)

Study the following electronic configuration and answer the questions given below.

(i) Identify the groups of B and D.

(ii) Out of the elements B and C, which is more reactive, why?

(iii) What is the valency of A and why?

iv) Write the molecular formula of compound formed by the combination C and D.

(i) B lies in group IA and D lies in group VIIA.

(ii) Element C is more reactive than element B because atomic size of element C is larger than element B hence element C can easily lose its valence electron than element B.

(iii) The valency of A is one(1) because it requires 1 extra electron to completely fill its valence shell.

(iv) The molecular formula of compound formed by the combination C and D is KCl.

Reason:-
Element C is Potassium(K) and element D is Chlorine (Cl). They reacts together to give potassium chloride (KCl).

5.b)

Draw a well labelled diagram to show the laboratory preparation of carbon dioxide gas. Write the name and structural formula of the compound formed due to the displacement of three hydrogen atoms of propane with three hydroxyle (OH) radicals.

Laboratory preparation of carbondioxide gas.

The name of the compound is Glycerol [C₃H₅(OH)₃].

Its IUPAC name is 1,2,3-Propanetriol.

Its structural formula is shown below:-

Structural formula of Glycerol

6.a)

Which metal is obtained from argentite ore? Write the balanced chemical equation when that metal is treated with conc. sulphuric acid. Write any two uses of acids. 

0.5+2+2=4.5 

Silver is obtained from argentite ore.

Silver reacts with hot concentrated sulphuric acid to give silver sulphate, sulphur dioxide and water.
The chemical reaction is given below :-
2Ag + conc 2H₂SO₄ → Ag₂SO₄ + SO₂ + 2H₂O


Uses of acids are as follows:-

(i) Lab chemical :- Acids like HCl, H₂SO₄, HNO₃ are frequently used chemicals in chemical laboratory.

(ii) Toilet cleaner :- Acids are used in toilet cleaner.

(iii) Battery :- Dilute H₂SO₄ is used inside lead-acid battery. This battery is used inside vehicles.

(iv) Washing powder :- Acid is used as an ingredient in detergent powder.

(v) Flavor :- Citric acid (C₆H₈O₇) is used as flavoring and preservatives in food.

(vi) Vitamer :- Pantothenic acid, folic acid and ascorbic acid are vitamers for vitaminin B₅, vitamin B₉ and vitamin C respectively.

(vii) Cosmetics :- Lactic acid [CH₃CH(OH)COOH] is used in cosmetics to adjust acidity and for its disinfectant and keratolytic properties.

(viii) Fertilizers :- Sulphuric acid and nitric acid are used for manufacturing fertilizers.

(ix) Antibacterial :- Benzoic acid prevents infection due to bacteria.

(x) Skin care :- Salicylic acid shed rough or dead skin cell.

(xi) Carbonated water :- Carbonic acid is used for making coke, soda-water etc.

(xii) Cervical cancer detection :- Acetic acid is used to detect cervical cancer during screening.

(xiii) Soap manufacture:- Long chain fatty acids of sodium and potassium are used for manufacturing soap. 

6.b)

Write two differences between soap and detergents. Give an adverse effect of chemical fertilizer.

Differences between soap and detergents are as follows:-

"Biology"

7.a)

Write full form of HIV. Name the three layers of meninges that cover the brain. Write two differences between taxis and tropism.

The full form of HIV is human immunodeficiency viruses.

The three layers of meninges that cover the brain are:-
(i)   Dura mater,
(ii)  Arachnoid mater
(iii) Pia mater.

The differences between taxis and tropism are as follows:-





7.b)

Draw the internal structure of human heart and show the parts right ventricle, pulmonary vein and bicuspid valve.

The internal structure of human heart is drawn below:-






8.a)

Study the mitosis cell division given in the figure and answer the following questions.

(i) Name the stage of the cell division shown in the figure.

(ii) Label the parts A, B, C and D.

(iii) Write any two characteristics of this stage.

(i) Anaphase stage is shown in the figure.

(ii)  A → Centrosome
      B →  Interpolar microtubules
      C → Chromosome
      D → Kinetochore

(iii) Characteristics of anaphase are as follows:-
         a.  Kinetochore microtubules shortens. 
         b. Chromosomes moves toward opposite poles of the cell.



8.b)

Why is vegetative propagation beneficial for farmers? What is alternation of generation in the life cycle of fern plants?

(a) Vegetative propagation allows plants to reach the mature phase faster.

(b) Desirable traits can be grown and yielded indefinitely as new plants are clones(Clone: Xerox, Photocopy) of their parent plant.

(c) It is suitable for growing plants having longer seed dormancy i.e. bear seeds after very long time. For example bamboos which bear seeds after 60 to 120 years depending upon species.

(d) It is suitable for growing plants which do not bear seeds at all.

                     Fern plants pass through two generation namely sporophytic generation and gametophytic generation to complete its life cycle in alternate way. This is called alternation of generation.


9.a)

Write two differences between gymnosperm and angiosperm. Mention two ways of changing atmospheric nitrogen into nitrate salt.

The differences between gymnosperm and angiosperm are given below:-





Ways of changing atmospheric nitrogen into nitrate salts are as follows:-

Lightning:- Lightning converts atmospheric nitrogen and oxygen into various nitrogen oxides(NOₓ). these nitrogen oxides react with rain water and fall on earth surface in form of nitrous and nitric acid.

Diazotrophic microorganism :- These microorganism are nitrogen fixing bacteria. They are present inside soil and convert atmospheric nitrogen into ammonia(NH₃)


9.b)

What is variation? Draw the chart of crossing red flowered pea plant and white flowered pea plant up to second filial generation.

Variation is diversity in gene frequencies which leads to differences between individuals or populations.

"Geology and Astronomy"

10.a)

What is fossils? Living beings were evolved millions of years after the earth was created, why? Statistical data shows that the average temperature in Nepal is increasing by 0.06ºC every year. Write two effects of it in Nepal.

Fossil is the remnant of dead plants and animals which died millions of years ago.
                The temperature of the earth when it was formed was very high so that water exists in vapour form. The earth cools down slowly by convection and large water mass body (ocean) is formed. Simple carbon compounds formation was gradually followed by complex carbon compounds formation like amines, proteins etc. A series of such chemical evolution in nature gives the very first life on the earth in form of unicellular microorganisms. All these change takes millions of years. That is why living beings were evolved millions of years after the earth is  created.

This temperature increase is due to global warming. Some effects of global warming in Nepal are as follows:-

(i) Drought
(ii) Snow melting accelerated
(iii) Lake outburst
(iv) Erosion and landslide
(v)Biodiversity decline
(vi) Heat wave in terai region
(vii) Extreme climatic conditions.



10.b)

Name the planet which has the largest number of satellites. 'A Comet is not actually a star'. Give two evidence in favour of this statement.