ADEPT YOURSELF
www.adeptyourself.com β’ Academic Excellence Series
CBSE CLASS IX β SCIENCE (CODE NO. 086)
SAMPLE QUESTION PAPER β SET 4 | ACADEMIC SESSION 2026β2027
General Instructions:
- The question paper comprises Five Sections: A, B, C, D and E. There are 39 questions in total.
- All questions are compulsory. However, an internal choice is provided in some questions.
- Section A consists of 20 objective type questions (Q1 to Q20) carrying 1 mark each. (Q1 to Q16 are MCQs, Q17 to Q20 are Assertion-Reasoning).
- Section B consists of 6 Very Short Answer type questions (Q21 to Q26) carrying 2 marks each.
- Section C consists of 7 Short Answer type questions (Q27 to Q33) carrying 3 marks each.
- Section D consists of 3 Long Answer type questions (Q34 to Q36) carrying 5 marks each.
- Section E consists of 3 Case-Based units of assessment (Q37 to Q39) carrying 4 marks each with sub-parts.
SECTION A β OBJECTIVE TYPE QUESTIONS (20 Marks)
Q1.
Which of the following conditions will increase the rate of evaporation of water?
[1]
Q2.
Which of the following is an example of a chemical change?
[1]
Q3.
Which organelle is referred to as the ‘protein factory’ of a cell?
[1]
Q4.
Cartilage is not found in which of the following body parts?
[1]
Q5.
A particle moves in a circular path of radius $r$. The displacement after completing half a circle is:
[1]
Q6.
Which of the following has the highest inertia?
[1]
Q7.
The value of acceleration due to gravity $g$ on the surface of the earth is minimum at the:
[1]
Q8.
What is the chemical formula of copper(II) sulphate?
[1]
Q9.
Plasmolysis in a plant cell is defined as:
[1]
Q10.
When a car turns around a sharp circular bend at constant speed, its:
[1]
Q11.
The maximum number of electrons that can be accommodated in the $M$-shell ($n=3$) of an atom is:
[1]
Q12.
Which of the following tissues is composed entirely of dead cells with heavily lignified cell walls?
[1]
Q13.
A force of $10\text{ N}$ moves an object through a distance of $2\text{ m}$ at an angle of $60^\circ$ to the direction of force. The work done is: [$\cos 60^\circ = 0.5$]
[1]
Q14.
Note is a sound:
[1]
Q15.
Which of the following is a bio-fertilizer that fixes atmospheric nitrogen in leguminous crop roots?
[1]
Q16.
What is the mass of $0.5\text{ mole}$ of water ($\text{H}_2\text{O}$) molecules?
[1]
Q17.
Assertion (A): When a bottle of perfume is opened in one corner of a room, its odor quickly spreads throughout the entire room.
Reason (R): Gaseous particles have large intermolecular spaces and high kinetic energy, facilitating rapid diffusion. [1]
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Reason (R): Gaseous particles have large intermolecular spaces and high kinetic energy, facilitating rapid diffusion. [1]
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Q18.
Assertion (A): A plant cell does not burst when placed in a hypotonic medium.
Reason (R): The presence of a rigid cellulose cell wall exerts counter wall pressure against swelling turgor pressure. [1]
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Reason (R): The presence of a rigid cellulose cell wall exerts counter wall pressure against swelling turgor pressure. [1]
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Q19.
Assertion (A): When an unbalanced external force acts on a body, it always produces acceleration.
Reason (R): Acceleration of an object is inversely proportional to its mass for a given applied force. [1]
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Reason (R): Acceleration of an object is inversely proportional to its mass for a given applied force. [1]
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Q20.
Assertion (A): The speed of sound in water is greater than the speed of sound in air.
Reason (R): Liquids have higher density and bulk modulus of elasticity compared to gases. [1]
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Reason (R): Liquids have higher density and bulk modulus of elasticity compared to gases. [1]
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
SECTION B β VERY SHORT ANSWER QUESTIONS (12 Marks)
Q21.
Differentiate between boiling and evaporation on two fundamental bases.
[2]
Q22.
Why are lysosomes called the ‘scavengers’ or ‘digestive bags’ of a cell?
[2]
Q23.
A bus accelerates uniformly from $36\text{ km/h}$ to $72\text{ km/h}$ in $10\text{ s}$. Calculate:
(a) The acceleration of the bus.
(b) The distance covered by the bus in this time. [2]
(a) The acceleration of the bus.
(b) The distance covered by the bus in this time. [2]
OR
State the law of conservation of momentum. Write its mathematical formula for two colliding bodies.
Q24.
What is the difference between the mass of an object and its weight?
[2]
Q25.
Name any two biotic factors and two abiotic factors that cause post-harvest storage losses in agricultural food grains.
[2]
Q26.
Write the molecular formula and calculate the molar mass of:
(a) Carbon dioxide ($\text{CO}_2$)
(b) Methane ($\text{CH}_4$) [2]
(a) Carbon dioxide ($\text{CO}_2$)
(b) Methane ($\text{CH}_4$) [2]
SECTION C β SHORT ANSWER QUESTIONS (21 Marks)
Q27.
(a) What is a saturated solution?
(b) How can a saturated solution be converted into an unsaturated solution without adding more solvent?
(c) What happens when a hot saturated solution of copper sulphate is allowed to cool down slowly? [3]
(b) How can a saturated solution be converted into an unsaturated solution without adding more solvent?
(c) What happens when a hot saturated solution of copper sulphate is allowed to cool down slowly? [3]
Q28.
Describe the structure, cellular components, and functions of Areolar connective tissue in animals.
[3]
Q29.
A constant force of $5\text{ N}$ acts on a body of mass $2\text{ kg}$ initially at rest for a duration of $4\text{ s}$. Calculate:
(a) The acceleration produced in the body.
(b) The final velocity attained.
(c) The distance travelled by the body during this time. [3]
(a) The acceleration produced in the body.
(b) The final velocity attained.
(c) The distance travelled by the body during this time. [3]
OR
State Archimedes’ Principle. Explain why an iron nail sinks in water, but a huge ship made of iron and steel floats on the ocean.
Q30.
(a) Define 1 Joule of work.
(b) A pair of bullocks exerts a force of $140\text{ N}$ on a plough. The field being ploughed is $15\text{ m}$ long. How much work is done in ploughing the length of the field?
(c) State the work-energy theorem. [3]
(b) A pair of bullocks exerts a force of $140\text{ N}$ on a plough. The field being ploughed is $15\text{ m}$ long. How much work is done in ploughing the length of the field?
(c) State the work-energy theorem. [3]
Q31.
(a) Explain the main postulates of Dalton’s Atomic Theory.
(b) State any one limitation of Dalton’s atomic model. [3]
(b) State any one limitation of Dalton’s atomic model. [3]
Q32.
Differentiate between voluntary muscles and involuntary muscles with respect to their structure, control, and location in the human body.
[3]
Q33.
What are weeds? Name two common agricultural weeds and explain two methods of controlling weed growth in crop fields.
[3]
SECTION D β LONG ANSWER QUESTIONS (15 Marks)
Q34.
(a) State the postulates of Neil Bohr’s model of the atom.
(b) Draw the Bohr atomic orbital model for:
(i) Carbon ($Z=6$, Mass number = 12)
(ii) Magnesium ($Z=12$, Mass number = 24)
(c) What is the electronic configuration and valency of an element having atomic number $Z = 15$? [5]
(b) Define isotopes and isobars. Give one example of each.
(c) An element $E$ exists as two isotopes: $^{79}_{35}\text{E}$ ($50\%$) and $^{81}_{35}\text{E}$ ($50\%$). Calculate the average atomic mass of the element $E$.
(b) Draw the Bohr atomic orbital model for:
(i) Carbon ($Z=6$, Mass number = 12)
(ii) Magnesium ($Z=12$, Mass number = 24)
(c) What is the electronic configuration and valency of an element having atomic number $Z = 15$? [5]
OR
(a) State the three rules of the Bohr-Bury scheme for electron filling in various shells.
(b) Define isotopes and isobars. Give one example of each.
(c) An element $E$ exists as two isotopes: $^{79}_{35}\text{E}$ ($50\%$) and $^{81}_{35}\text{E}$ ($50\%$). Calculate the average atomic mass of the element $E$.
Q35.
(a) What is the role of the Golgi apparatus in a living cell? List four important functions.
(b) Differentiate between cytoplasm and nucleoplasm.
(c) Why are chloroplasts called the photosynthetic kitchens of plant cells? [5]
(b) What are stomata? Describe the mechanism of opening and closing of stomata.
(c) Why are epidermal cells on the aerial parts of desert plants covered with a waxy cutin layer?
(b) Differentiate between cytoplasm and nucleoplasm.
(c) Why are chloroplasts called the photosynthetic kitchens of plant cells? [5]
OR
(a) What are protective tissues in plants? Describe the structure and functions of Epidermis and Cork.
(b) What are stomata? Describe the mechanism of opening and closing of stomata.
(c) Why are epidermal cells on the aerial parts of desert plants covered with a waxy cutin layer?
Q36.
(a) State Newton’s Second Law of Motion. Derive the mathematical relation $F = ma$.
(b) A body of mass $2\text{ kg}$ is sliding with a constant velocity of $4\text{ m/s}$ on a frictionless horizontal table. What is the force required to keep the body moving with the same velocity?
(c) A motor vehicle of mass $1500\text{ kg}$ is stopped from a speed of $20\text{ m/s}$ in $50\text{ m}$. Calculate the retarding force exerted by the brakes. [5]
(b) A simple pendulum of mass $m$ is swinging between extreme positions $A$ and $B$ through mean position $O$. Explain how energy is conserved at each point during its oscillation.
(c) An electric motor of $2\text{ kW}$ lifts $1000\text{ litres}$ of water to an overhead tank at a height of $18\text{ m}$ in $1.5\text{ minutes}$. Calculate the work done and efficiency of the motor. [Density of water $= 1\text{ kg/litre}$, $g = 10\text{ m/s}^2$]
(b) A body of mass $2\text{ kg}$ is sliding with a constant velocity of $4\text{ m/s}$ on a frictionless horizontal table. What is the force required to keep the body moving with the same velocity?
(c) A motor vehicle of mass $1500\text{ kg}$ is stopped from a speed of $20\text{ m/s}$ in $50\text{ m}$. Calculate the retarding force exerted by the brakes. [5]
OR
(a) State the Law of Conservation of Energy.
(b) A simple pendulum of mass $m$ is swinging between extreme positions $A$ and $B$ through mean position $O$. Explain how energy is conserved at each point during its oscillation.
(c) An electric motor of $2\text{ kW}$ lifts $1000\text{ litres}$ of water to an overhead tank at a height of $18\text{ m}$ in $1.5\text{ minutes}$. Calculate the work done and efficiency of the motor. [Density of water $= 1\text{ kg/litre}$, $g = 10\text{ m/s}^2$]
SECTION E β CASE-BASED INTEGRATED UNITS (12 Marks)
Q37. Read the following source carefully and answer the questions that follow:
[4](a) Classify the following into elements and compounds: (i) Iron, (ii) Water, (iii) Methane, (iv) Gold. [1]
(b) Mention one property in which a compound differs from its constituent elements. [1]
(c) State two fundamental differences between a mixture and a chemical compound. [2]
Matter can be classified on the basis of chemical composition into pure substances (elements and compounds) and mixtures (homogeneous and heterogeneous). Elements are pure substances that cannot be broken down into simpler substances by chemical reactions. Compounds are composed of two or more elements chemically combined in fixed proportions by mass. Mixtures contain two or more pure substances mixed in any proportion without chemical bonding.
(b) Mention one property in which a compound differs from its constituent elements. [1]
(c) State two fundamental differences between a mixture and a chemical compound. [2]
OR
Why is air considered a homogeneous mixture rather than a chemical compound? State two reasons. [2]
Q38. Read the following source carefully and answer the questions that follow:
[4](a) At what point of vertical flight is the kinetic energy of a thrown ball maximum? [1]
(b) What is the total mechanical energy of an object of mass $m$ at its maximum height $h$? [1]
(c) An object of mass $20\text{ kg}$ is dropped from a height of $10\text{ m}$. Calculate its kinetic energy when it has fallen through a distance of $4\text{ m}$. [Take $g = 10\text{ m/s}^2$] [2]
When an object is thrown vertically upwards, its initial kinetic energy is gradually converted into gravitational potential energy. At the highest point, its velocity becomes zero and its entire energy is potential energy. As it falls back towards the earth under gravity, its potential energy is converted back into kinetic energy. According to the law of conservation of mechanical energy, the sum of kinetic and potential energy ($E = KE + PE$) remains constant at all points during free fall in the absence of air resistance.
(b) What is the total mechanical energy of an object of mass $m$ at its maximum height $h$? [1]
(c) An object of mass $20\text{ kg}$ is dropped from a height of $10\text{ m}$. Calculate its kinetic energy when it has fallen through a distance of $4\text{ m}$. [Take $g = 10\text{ m/s}^2$] [2]
OR
Calculate the velocity of a $20\text{ kg}$ body just before striking the ground when dropped from a height of $10\text{ m}$. [Take $g = 10\text{ m/s}^2$] [2]
Q39. Read the following source carefully and answer the questions that follow:
[4](a) Name the scientific branch of farming dealing with honey bees. [1]
(b) Name one indigenous and one exotic bee variety commonly used in Indian apiculture. [1]
(c) What is ‘pasturage’ in apiculture and how does it determine the commercial quality of honey? [2]
Beekeeping (apiculture) is low-investment agricultural enterprise practiced by farmers for honey and beeswax production. Beehives are established in pastures with abundant flora (pasturage) providing nectar and pollen. The quality and taste of honey depend upon the pasturage and flowers available to the bees. For commercial honey production, the Italian bee variety (Apis mellifera) has been widely introduced in India alongside indigenous species such as Apis cerana indica (Indian bee) and Apis dorsata (rock bee).
(b) Name one indigenous and one exotic bee variety commonly used in Indian apiculture. [1]
(c) What is ‘pasturage’ in apiculture and how does it determine the commercial quality of honey? [2]
OR
State two advantages of introducing the Italian bee variety (Apis mellifera) in commercial apiaries. [2]
CBSE CLASS IX SCIENCE (086) β SOLUTIONS & MARKING SCHEME β SET 4
SECTION A β ANSWERS
Q1. (a) Increase in temperature of water [1]
Q2. (b) Burning of a candle [1]
Q3. (b) Ribosome [1]
Q4. (c) Kidney [1]
Q5. (c) $2r$ (Diameter between opposite endpoints) [1]
Q6. (d) A train of mass $20000\text{ kg}$ (Inertia is directly proportional to mass) [1]
Q7. (c) Equator (Earth’s equatorial radius is maximum, $g \propto 1/R^2$) [1]
Q8. (a) $\text{CuSO}_4$ [1]
Q9. (b) Shrinkage of cytoplasm in hypertonic medium [1]
Q10. (c) Velocity changes due to continuous change in direction [1]
Q11. (c) 18 [$2n^2 = 2(3)^2 = 18$] [1]
Q12. (c) Sclerenchyma [1]
Q13. (b) $10\text{ J}$ [$W = F s \cos 60^\circ = 10 \times 2 \times 0.5 = 10\text{ J}$] [1]
Q14. (b) Of a mixture of several frequencies [1]
Q15. (a) Rhizobium [1]
Q16. (b) $9\text{ g}$ [$0.5 \times 18\text{ g/mol} = 9\text{ g}$] [1]
Q17. (a) Both A and R are true and R is the correct explanation of A. [1]
Q18. (a) Both A and R are true and R is the correct explanation of A. [1]
Q19. (b) Both A and R are true but R is not the correct explanation of A. [1]
Q20. (a) Both A and R are true and R is the correct explanation of A. [1]
SECTION B β ANSWERS
Q21.
- Boiling: Bulk phenomenon, occurs only at a fixed boiling point throughout the liquid, produces bubbles.
- Evaporation: Surface phenomenon, occurs at all temperatures below boiling point, causes cooling.
Q22.
Lysosomes contain powerful hydrolytic digestive enzymes that break down foreign pathogens, damaged organelles, and cellular debris, keeping the cell clean and recycling organic materials. [2]
Q23.
Given: $u = 36\text{ km/h} = 10\text{ m/s}$, $v = 72\text{ km/h} = 20\text{ m/s}$, $t = 10\text{ s}$.
(a) Acceleration $a = \frac{v – u}{t} = \frac{20 – 10}{10} = \mathbf{1\text{ m/s}^2}$.
(b) Distance $s = ut + \frac{1}{2}at^2 = (10 \times 10) + \frac{1}{2}(1)(10)^2 = 100 + 50 = \mathbf{150\text{ m}}$. [2]
OR
(a) Acceleration $a = \frac{v – u}{t} = \frac{20 – 10}{10} = \mathbf{1\text{ m/s}^2}$.
(b) Distance $s = ut + \frac{1}{2}at^2 = (10 \times 10) + \frac{1}{2}(1)(10)^2 = 100 + 50 = \mathbf{150\text{ m}}$. [2]
OR
- Law of Conservation of Momentum: The total momentum of an isolated system remains constant if no external unbalanced force acts on it.
- Formula: $m_1 u_1 + m_2 u_2 = m_1 v_1 + m_2 v_2$.
Q24.
- Mass: Measure of the quantity of matter in a body; scalar quantity, measured in kg, remains constant everywhere.
- Weight: Gravitational force acting on a body ($W = mg$); vector quantity, measured in Newtons (N), varies with local acceleration due to gravity $g$.
Q25.
- Biotic factors: Insects, rodents (rats), fungi, bacteria, mites.
- Abiotic factors: Inappropriate moisture content in grains, high environmental temperature in storage godowns.
Q26.
- (a) $\text{CO}_2$: Molar mass $= 12 + 2(16) = 12 + 32 = \mathbf{44\text{ g/mol}}$.
- (b) $\text{CH}_4$: Molar mass $= 12 + 4(1) = 12 + 4 = \mathbf{16\text{ g/mol}}$.
SECTION C β ANSWERS
Q27.
- (a) Saturated Solution: A solution in which no more solute can be dissolved at a given specified temperature.
- (b) By heating the solution to a higher temperature (solubility increases with temperature).
- (c) Pure blue crystals of copper sulphate ($\text{CuSO}_4\cdot 5\text{H}_2\text{O}$) separate out from the solution through crystallization.
Q28.
- Location: Found between skin and muscles, around blood vessels, nerves, and in bone marrow.
- Structure: Loose connective tissue composed of fibroblasts, macrophages, mast cells, and collagen/elastin fibres suspended in a gelatinous matrix.
- Functions: Fills spaces inside organs, supports internal delicate organs, and assists in tissue repair following injury.
Q29.
Given: $F = 5\text{ N}$, $m = 2\text{ kg}$, $u = 0$, $t = 4\text{ s}$.
(a) $a = \frac{F}{m} = \frac{5}{2} = \mathbf{2.5\text{ m/s}^2}$.
(b) $v = u + at = 0 + (2.5 \times 4) = \mathbf{10\text{ m/s}}$.
(c) $s = ut + \frac{1}{2}at^2 = 0 + \frac{1}{2}(2.5)(4)^2 = 1.25 \times 16 = \mathbf{20\text{ m}}$. [3]
OR
(a) $a = \frac{F}{m} = \frac{5}{2} = \mathbf{2.5\text{ m/s}^2}$.
(b) $v = u + at = 0 + (2.5 \times 4) = \mathbf{10\text{ m/s}}$.
(c) $s = ut + \frac{1}{2}at^2 = 0 + \frac{1}{2}(2.5)(4)^2 = 1.25 \times 16 = \mathbf{20\text{ m}}$. [3]
OR
- An iron nail has a small volume; the weight of water it displaces is less than its own weight (density of iron > density of water), so it sinks.
- A ship is hollow and contains large air spaces; its average density is much lower than water, and it displaces a volume of water whose weight is equal to the total weight of the ship, allowing it to float.
Q30.
- (a) 1 Joule: The amount of work done when a force of 1 Newton displaces an object through a distance of 1 metre in the direction of the force ($1\text{ J} = 1\text{ N}\cdot\text{m}$).
- (b) Work done $W = F \times s = 140\text{ N} \times 15\text{ m} = \mathbf{2100\text{ Joules}}$.
- (c) Work-Energy Theorem: The work done by the net force acting on a body is equal to the change in its kinetic energy ($W = \Delta KE = \frac{1}{2}mv^2 – \frac{1}{2}mu^2$).
Q31.
- (a) Dalton’s Postulates:
1. All matter is made of tiny indivisible particles called atoms.
2. Atoms of a given element are identical in mass and chemical properties.
3. Atoms combine in the ratio of small whole numbers to form compounds.
4. Atoms can neither be created nor destroyed in a chemical reaction. - (b) Limitation: Atoms are divisible into subatomic particles (electrons, protons, neutrons), and isotopes show that atoms of the same element can have different masses.
Q32.
- Voluntary (Striated) Muscles: Long, cylindrical, unbranched multinucleated cells with dark/light bands; under conscious control; attached to skeleton (biceps, triceps, leg muscles).
- Involuntary (Smooth) Muscles: Spindle-shaped, uninucleate cells without striations; not under conscious control; located in visceral organ walls (stomach, intestines, iris, ureters).
Q33.
- Weeds: Unwanted plants that grow along with cultivated crops (e.g., Xanthium / Gokhroo, Parthenium / Gajar ghas, Cyperinus rotundus / Motha).
- Control Methods:
1. Mechanical removal: Uprooting or weeding with a khurpi / ploughing before sowing.
2. Chemical method: Spraying weedicides (e.g., 2,4-D) at appropriate vegetative stages.
SECTION D β ANSWERS
Q34.
OR
- (a) Bohr’s Postulates:
1. Electrons revolve around the nucleus only in certain discrete, non-radiating orbits (energy levels).
2. While revolving in these discrete orbits, electrons do not radiate energy. - (b) Orbital diagrams:
(i) Carbon ($Z=6$): Configuration = $2, 4$ (K=2, L=4).
(ii) Magnesium ($Z=12$): Configuration = $2, 8, 2$ (K=2, L=8, M=2). - (c) Element with $Z = 15$ (Phosphorus):
Electronic configuration = $\mathbf{2, 8, 5}$ (K=2, L=8, M=5).
Valency $= 8 – 5 = \mathbf{3}$ (or 3, 5).
OR
- (a) Bohr-Bury Scheme:
1. Maximum electrons in $n^{\text{th}}$ shell $= 2n^2$.
2. Outermost shell cannot hold more than 8 electrons.
3. Electrons do not enter a new shell unless inner shells are filled. - (b) Isotopes: $^{1}_{1}\text{H}, ^{2}_{1}\text{H}, ^{3}_{1}\text{H}$; Isobars: $^{40}_{18}\text{Ar}, ^{40}_{20}\text{Ca}$.
- (c) Average atomic mass $= \frac{79 \times 50 + 81 \times 50}{100} = \frac{3950 + 4050}{100} = \frac{8000}{100} = \mathbf{80\text{ u}}$.
Q35.
OR
- (a) Functions of Golgi Apparatus:
1. Packaging, modification, and storage of secretory products in vesicles.
2. Synthesis of complex sugars from simple sugars.
3. Formation and dispatch of primary lysosomes.
4. Secretion of cell wall and plasma membrane materials. - (b) Cytoplasm vs Nucleoplasm: Cytoplasm is the fluid matrix outside the nucleus enclosing metabolic organelles; Nucleoplasm is the dense fluid inside the nuclear membrane containing chromatin and nucleolus.
- (c) Chloroplasts contain the green pigment **chlorophyll**, which traps solar energy to convert carbon dioxide and water into glucose (food) via photosynthesis.
OR
- (a) Epidermis: Outermost single-layer protective tissue covering leaves, stem, and roots; prevents mechanical injury, water loss, and infection.
Cork: Secondary protective tissue formed on mature stems/roots; dead cells with suberin walls providing fire, frost, and physical protection. - (b) Stomata: Pores regulated by turgor changes in guard cells; guard cells swell with water intake and curve outwards (opening), and shrink upon water loss (closing).
- (c) Cutin is a water-impermeable waxy substance that minimizes water loss via transpiration in arid desert conditions.
Q36.
OR
- (a) Newton’s Second Law: Rate of change of momentum of an object is directly proportional to applied unbalanced force in the direction of the force.
Derivation: Momentum $p_1 = mu$, $p_2 = mv \Rightarrow \Delta p = m(v – u)$.
Rate of change of momentum $= \frac{m(v – u)}{t} = ma$.
Therefore, $F \propto ma \Rightarrow \mathbf{F = ma}$ (where constant $k=1$). - (b) Since the table is frictionless and velocity is constant ($a=0$), the external force required is $\mathbf{0\text{ N}}$ ($F = ma = 2 \times 0 = 0$).
- (c) $m = 1500\text{ kg}$, $u = 20\text{ m/s}$, $v = 0$, $s = 50\text{ m}$.
$v^2 = u^2 + 2as \Rightarrow 0 = 400 + 2a(50) \Rightarrow 100a = -400 \Rightarrow a = -4\text{ m/s}^2$.
Retarding Force $F = m \times a = 1500 \times (-4) = \mathbf{-6000\text{ N}}$ (Magnitude = $6000\text{ N}$).
OR
- (a) Conservation of Energy: Total mechanical energy of an isolated system remains constant during transformation.
- (b) Simple Pendulum:
1. At extreme positions (A and B): Velocity $= 0 \Rightarrow KE = 0$, $PE = \text{maximum}$.
2. At mean position (O): Height $= 0 \Rightarrow PE = 0$, Velocity is maximum $\Rightarrow KE = \text{maximum}$.
3. At intermediate points: Energy is partly kinetic and partly potential, with $KE + PE = \text{constant}$. - (c) Mass of water $m = 1000\text{ kg}$, Height $h = 18\text{ m}$, Time $t = 1.5\text{ min} = 90\text{ s}$, Input Power $= 2\text{ kW} = 2000\text{ W}$.
Work Done $W = mgh = 1000 \times 10 \times 18 = \mathbf{1,80,000\text{ J}}$ ($180\text{ kJ}$).
Output Power $P_{\text{out}} = \frac{1,80,000}{90} = 2000\text{ W}$.
Efficiency $= \frac{P_{\text{out}}}{P_{\text{in}}} \times 100 = \frac{2000}{2000} \times 100 = \mathbf{100\%}$.
SECTION E β ANSWERS
Q37.
- (a) Elements: Iron, Gold; Compounds: Water ($\text{H}_2\text{O}$), Methane ($\text{CH}_4$). [1]
- (b) The properties of a compound are entirely different from those of its constituent elements (e.g., water is a non-flammable liquid extinguisher, while hydrogen is combustible and oxygen supports combustion). [1]
- (c)
1. Composition: Mixtures have variable composition; compounds have fixed composition by mass.
2. Separation: Constituents of mixtures can be separated by physical methods; compounds require chemical/electrochemical methods. [2]
Q38.
- (a) At the lowest point (point of release/projection) where velocity is maximum. [1]
- (b) Total mechanical energy $E = mgh$. [1]
- (c) Loss in $PE = \text{Gain in } KE$.
When fallen $4\text{ m}$, $h_{\text{fallen}} = 4\text{ m}$.
$KE = m \times g \times h_{\text{fallen}} = 20 \times 10 \times 4 = \mathbf{800\text{ Joules}}$. [2]
Q39.
- (a) Apiculture. [1]
- (b) Indigenous: Apis cerana indica; Exotic: Apis mellifera (Italian bee). [1]
- (c) Pasturage refers to the flowers and vegetation available to honeybees for nectar and pollen collection. The flora type determines the taste, aroma, color, and commercial quality of the honey. [2]