Science Practice Questions

Physics

Motion — Class 9

1 A car accelerates uniformly from $18\text{ km/h}$ to $36\text{ km/h}$ in $5$ seconds. Calculate the acceleration and the distance covered.

Answer: $a = 1\text{ m/s}^2$, $s = 37.5\text{ m}$

Convert to m/s: $u = 5\text{ m/s}$, $v = 10\text{ m/s}$. $a = \frac{v-u}{t} = \frac{10-5}{5} = 1\text{ m/s}^2$. $s = ut + \frac{1}{2}at^2 = 5(5) + \frac{1}{2}(1)(25) = 25 + 12.5 = 37.5\text{ m}$

Force & Laws of Motion — Class 9

2 A bullet of mass $10\text{ g}$ is fired with a velocity of $200\text{ m/s}$ from a gun of mass $4\text{ kg}$. Find the recoil velocity of the gun.

Answer: $0.5\text{ m/s}$ (backward)

Conservation of momentum: $m_b v_b + m_g v_g = 0$. $0.01 \times 200 + 4 \times v_g = 0$. $v_g = -\frac{2}{4} = -0.5\text{ m/s}$

Gravitation — Class 9

3 A stone is dropped from the top of a tower $80\text{ m}$ high. How long does it take to reach the ground? ($g = 10\text{ m/s}^2$)

Answer: $4\text{ seconds}$

$h = \frac{1}{2}gt^2$, so $80 = \frac{1}{2} \times 10 \times t^2$, $80 = 5t^2$, $t^2 = 16$, $t = 4\text{ s}$

Light — Reflection — Class 10

4 An object is placed at $30\text{ cm}$ from a concave mirror of focal length $20\text{ cm}$. Find the position, nature, and magnification of the image.

Answer: $v = -60\text{ cm}$ (Real, inverted, magnified), $m = -2$

$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$. $\frac{1}{-20} = \frac{1}{v} + \frac{1}{-30}$. $\frac{1}{v} = \frac{-1}{20} + \frac{1}{30} = \frac{-3+2}{60} = \frac{-1}{60}$. $v = -60\text{ cm}$. $m = -\frac{v}{u} = -\frac{-60}{-30} = -2$

Electricity — Class 10

5 Two resistors of $4\;\Omega$ and $6\;\Omega$ are connected in parallel across a $12\text{ V}$ battery. Find the total current drawn.

Answer: $5\text{ A}$

$\frac{1}{R_p} = \frac{1}{4} + \frac{1}{6} = \frac{3+2}{12} = \frac{5}{12}$. $R_p = \frac{12}{5} = 2.4\;\Omega$. $I = \frac{V}{R} = \frac{12}{2.4} = 5\text{ A}$

Magnetic Effects — Class 10

6 State Fleming's Left Hand Rule. What force acts on a conductor of length $0.5\text{ m}$ carrying $4\text{ A}$ current placed perpendicular to a magnetic field of $0.2\text{ T}$?

Answer: $F = 0.4\text{ N}$

Fleming's Left Hand Rule: Thumb (Force), Forefinger (Field), Middle finger (Current). $F = BIL = 0.2 \times 4 \times 0.5 = 0.4\text{ N}$

Chemistry

Chemical Reactions — Class 10

1 Balance the equation: $\text{Fe} + \text{H}_2\text{O} \rightarrow \text{Fe}_3\text{O}_4 + \text{H}_2$

Answer: $3\text{Fe} + 4\text{H}_2\text{O} \rightarrow \text{Fe}_3\text{O}_4 + 4\text{H}_2$

Acids, Bases & Salts — Class 10

2 What is the pH of a solution with $[\text{H}^+] = 1 \times 10^{-9}\text{ mol/L}$? Is it acidic, basic, or neutral?

Answer: pH = $9$, Basic

$\text{pH} = -\log[\text{H}^+] = -\log(10^{-9}) = 9$. Since pH > 7, the solution is basic.

Metals & Non-Metals — Class 10

3 Why is sodium kept immersed in kerosene oil? Write the reaction of sodium with water.

Sodium is highly reactive and catches fire on contact with moisture in air. Reaction: $2\text{Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2 \uparrow$ (vigorous, exothermic)

Carbon Compounds — Class 10

4 Draw the electron dot structure and write the molecular formula of ethane ($\text{C}_2\text{H}_6$).

Formula: $\text{C}_2\text{H}_6$. Structure: Each carbon forms 4 covalent bonds — one C–C bond and three C–H bonds per carbon. All 8 atoms satisfy the octet/duet rule.

Periodic Classification — Class 10

5 An element has atomic number 17. Identify its group, period, and classify as metal/non-metal.

Answer: Chlorine (Cl). Group 17, Period 3, Non-metal.

Electronic configuration: 2, 8, 7. 7 valence electrons → Group 17 (Halogen). 3 shells → Period 3.

Biology

Life Processes — Class 10

1 Explain the process of photosynthesis with the balanced chemical equation.

$6\text{CO}_2 + 12\text{H}_2\text{O} \xrightarrow[\text{Chlorophyll}]{\text{Sunlight}} \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 + 6\text{H}_2\text{O}$. Occurs in chloroplasts. Raw materials: CO₂ (from air through stomata) and H₂O (from soil through roots). Products: Glucose and Oxygen.

Control & Coordination — Class 10

2 What is a reflex arc? Draw and explain the path of a reflex action with an example.

A reflex arc is the neural pathway that controls a reflex action. Path: Receptor → Sensory neuron → Spinal cord → Motor neuron → Effector (muscle/gland). Example: Touching a hot object → hand withdraws instantly. The spinal cord processes this without involving the brain, making it faster.

Heredity — Class 10

3 In pea plants, tall (T) is dominant over dwarf (t). What will be the phenotypic ratio in the F2 generation of a monohybrid cross?

Answer: $3:1$ (Tall : Dwarf)

P: TT × tt. F1: All Tt (tall). F2: Self-cross Tt × Tt → TT, Tt, Tt, tt. Genotypic ratio 1:2:1, Phenotypic ratio 3 Tall : 1 Dwarf.

Cell Biology — Class 9

4 Differentiate between mitochondria and chloroplasts (at least 3 differences).

1. Mitochondria: site of cellular respiration; Chloroplasts: site of photosynthesis. 2. Mitochondria present in both plant and animal cells; Chloroplasts only in plant cells. 3. Mitochondria release energy (ATP); Chloroplasts trap solar energy.

Human Physiology — Class 10

5 Describe the path of blood through the human heart (double circulation).

Pulmonary circulation: Right ventricle → Pulmonary artery → Lungs (oxygenation) → Pulmonary veins → Left atrium. Systemic circulation: Left ventricle → Aorta → Body tissues → Vena cava → Right atrium. This is double circulation — blood passes through the heart twice per complete cycle.

Physics

Chemistry

Biology

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