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NCERT Class 11 Physics Chapter 1 Questions and Answers PDF
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| Class 11 Physics Chapter 1 Units and Measurements with NCERT solutions and practice questions. |
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NCERT Class 11 Physics
Chapter 1: Units and Measurements
Exercise 1.1
Q1(a). The volume of a cube of side 1 cm is equal to ____ m³.
Answer:
Volume = (1 cm)³ = 1 cm³
1 cm = 10⁻² m
1 cm³ = (10⁻²)³ m³
= 10⁻⁶ m³
Final Answer: 1 × 10⁻⁶ m³
Volume = (1 cm)³ = 1 cm³
1 cm = 10⁻² m
1 cm³ = (10⁻²)³ m³
= 10⁻⁶ m³
Final Answer: 1 × 10⁻⁶ m³
Q1(b). The surface area of a solid cylinder of radius 2.0 cm and height 10.0 cm is equal to ____ (mm)².
Answer:
Surface Area = 2πr(r+h)
= 2 × 3.14 × 2.0 × (2.0 + 10.0)
= 150.72 cm²
1 cm² = 100 mm²
150.72 × 100 = 15072 mm²
Final Answer: 1.5 × 10⁴ mm²
Surface Area = 2πr(r+h)
= 2 × 3.14 × 2.0 × (2.0 + 10.0)
= 150.72 cm²
1 cm² = 100 mm²
150.72 × 100 = 15072 mm²
Final Answer: 1.5 × 10⁴ mm²
Q1(c). A vehicle moving with a speed of 18 km h⁻¹ covers ____ m in 1 s.
Answer:
18 km h⁻¹ = 18 × (1000/3600)
= 5 m s⁻¹
Distance = Speed × Time
= 5 × 1
= 5 m
Final Answer: 5 m
18 km h⁻¹ = 18 × (1000/3600)
= 5 m s⁻¹
Distance = Speed × Time
= 5 × 1
= 5 m
Final Answer: 5 m
Q1(d). The relative density of lead is 11.3. Its density is ____ g cm⁻³ or ____ kg m⁻³.
Answer:
Density = Relative Density × Density of Water
= 11.3 × 1
= 11.3 g cm⁻³
1 g cm⁻³ = 1000 kg m⁻³
11.3 × 1000 = 1.13 × 10⁴ kg m⁻³
Final Answer:
11.3 g cm⁻³
1.13 × 10⁴ kg m⁻³
Density = Relative Density × Density of Water
= 11.3 × 1
= 11.3 g cm⁻³
1 g cm⁻³ = 1000 kg m⁻³
11.3 × 1000 = 1.13 × 10⁴ kg m⁻³
Final Answer:
11.3 g cm⁻³
1.13 × 10⁴ kg m⁻³
Exercise 1.2
Q2(a). 1 kg m² s⁻² = ____ g cm² s⁻²
Answer:
1 kg = 10³ g
1 m² = 10⁴ cm²
1 kg m² s⁻²
= 10³ × 10⁴ g cm² s⁻²
= 10⁷ g cm² s⁻²
Final Answer: 10⁷ g cm² s⁻²
1 kg = 10³ g
1 m² = 10⁴ cm²
1 kg m² s⁻²
= 10³ × 10⁴ g cm² s⁻²
= 10⁷ g cm² s⁻²
Final Answer: 10⁷ g cm² s⁻²
Q2(b). 1 m = ____ ly
Answer:
1 light year = 9.46 × 10¹⁵ m
1 m = 1 / (9.46 × 10¹⁵)
= 1.06 × 10⁻¹⁶ ly
Final Answer: 1.06 × 10⁻¹⁶ ly
1 light year = 9.46 × 10¹⁵ m
1 m = 1 / (9.46 × 10¹⁵)
= 1.06 × 10⁻¹⁶ ly
Final Answer: 1.06 × 10⁻¹⁶ ly
Q2(c). 3.0 m s⁻² = ____ km h⁻²
Answer:
1 m = 10⁻³ km
1 s = 1/3600 h
3.0 × 10⁻³ × (3600)²
= 38880 km h⁻²
Final Answer: 3.9 × 10⁴ km h⁻²
1 m = 10⁻³ km
1 s = 1/3600 h
3.0 × 10⁻³ × (3600)²
= 38880 km h⁻²
Final Answer: 3.9 × 10⁴ km h⁻²
Q2(d). G = 6.67 × 10⁻¹¹ N m² (kg)⁻² = ____ cm³ s⁻² g⁻¹
Answer:
1 N = kg m s⁻²
G = 6.67 × 10⁻¹¹ m³ kg⁻¹ s⁻²
1 m³ = 10⁶ cm³
1 kg⁻¹ = 10⁻³ g⁻¹
G = 6.67 × 10⁻¹¹ × 10⁶ × 10⁻³
= 6.67 × 10⁻⁸ cm³ s⁻² g⁻¹
Final Answer: 6.67 × 10⁻⁸ cm³ s⁻² g⁻¹
1 N = kg m s⁻²
G = 6.67 × 10⁻¹¹ m³ kg⁻¹ s⁻²
1 m³ = 10⁶ cm³
1 kg⁻¹ = 10⁻³ g⁻¹
G = 6.67 × 10⁻¹¹ × 10⁶ × 10⁻³
= 6.67 × 10⁻⁸ cm³ s⁻² g⁻¹
Final Answer: 6.67 × 10⁻⁸ cm³ s⁻² g⁻¹
Class 11 Physics - Units and Measurements
20 Practice Questions with Answers
Q1. A cube has a side of 2 cm. Find its volume.
Volume = a³
= 2³
= 8 cm³
Answer: 8 cm³
= 2³
= 8 cm³
Answer: 8 cm³
Q2. Convert 500 cm into metres.
500 ÷ 100 = 5 m
Answer: 5 m
Answer: 5 m
Q3. Convert 1 km into metres.
1 km = 1000 m
Answer: 1000 m
Answer: 1000 m
Q4. Convert 72 km h⁻¹ into m s⁻¹.
72 × (1000/3600)
= 20 m s⁻¹
Answer: 20 m s⁻¹
= 20 m s⁻¹
Answer: 20 m s⁻¹
Q5. A body moves with a speed of 15 m s⁻¹ for 4 s. Find the distance covered.
Distance = Speed × Time
= 15 × 4
= 60 m
Answer: 60 m
= 15 × 4
= 60 m
Answer: 60 m
Q6. Convert 1 m² into cm².
1 m = 100 cm
1 m² = (100)² cm²
= 10000 cm²
Answer: 10000 cm²
1 m² = (100)² cm²
= 10000 cm²
Answer: 10000 cm²
Q7. Find the area of a square of side 5 m.
Area = side²
= 5²
= 25 m²
Answer: 25 m²
= 5²
= 25 m²
Answer: 25 m²
Q8. Convert 1 litre into cm³.
1 litre = 1000 cm³
Answer: 1000 cm³
Answer: 1000 cm³
Q9. A body has mass 200 g and volume 50 cm³. Find density.
Density = Mass / Volume
= 200 / 50
= 4 g cm⁻³
Answer: 4 g cm⁻³
= 200 / 50
= 4 g cm⁻³
Answer: 4 g cm⁻³
Q10. What is the SI unit of force?
Answer: Newton (N)
Q11. What is the SI unit of energy?
Answer: Joule (J)
Q12. Convert 3 kg into grams.
3 × 1000 = 3000 g
Answer: 3000 g
Answer: 3000 g
Q13. Convert 2500 g into kilograms.
2500 ÷ 1000 = 2.5 kg
Answer: 2.5 kg
Answer: 2.5 kg
Q14. Find the total surface area of a cube of side 4 cm.
TSA = 6a²
= 6 × 4²
= 6 × 16
= 96 cm²
Answer: 96 cm²
= 6 × 4²
= 6 × 16
= 96 cm²
Answer: 96 cm²
Q15. What is the SI unit of time?
Answer: Second (s)
Q16. A cyclist covers 120 m in 20 s. Find speed.
Speed = Distance / Time
= 120 / 20
= 6 m s⁻¹
Answer: 6 m s⁻¹
= 120 / 20
= 6 m s⁻¹
Answer: 6 m s⁻¹
Q17. Convert 36 km h⁻¹ into m s⁻¹.
36 × (1000 / 3600)
= 10 m s⁻¹
Answer: 10 m s⁻¹
= 10 m s⁻¹
Answer: 10 m s⁻¹
Q18. What is the relative density of water?
Answer: 1
Q19. Find the volume of a cylinder of radius 3 cm and height 7 cm.
Volume = πr²h
= (22/7) × 3² × 7
= 198 cm³
Answer: 198 cm³
= (22/7) × 3² × 7
= 198 cm³
Answer: 198 cm³
Q20. Express 1 day in seconds.
1 day = 24 × 60 × 60
= 86400 s
Answer: 86400 s
= 86400 s
Answer: 86400 s
Quick Revision
- SI unit of length = metre (m)
- SI unit of mass = kilogram (kg)
- SI unit of time = second (s)
- SI unit of force = newton (N)
- SI unit of energy = joule (J)
- 1 km = 1000 m
- 1 m = 100 cm
- 1 litre = 1000 cm³
- Density = Mass / Volume
- Speed = Distance / Time
