Imp Questions For All Chapters – General Science Class 7
Measurement of Physical Quantities
Short Questions
1. What is a physical quantity?
→ A physical quantity is a property of matter that can be measured, such as mass, weight, distance, or temperature.
2. Give two examples of scalar quantities.
→ Mass and temperature are scalar quantities.
3. Give two examples of vector quantities.
→ Velocity and displacement are vector quantities.
4. What is mass?
→ Mass is the amount of matter in an object and is measured in kilograms or grams.
5. What is weight?
→ Weight is the gravitational force acting on an object and is measured in Newtons (N).
6. Why does the weight of an object change from place to place?
→ Weight depends on gravity, which varies at different places like poles, equator, or on different planets.
7. What is inertia?
→ The tendency of an object to resist a change in its state of motion is called inertia.
8. Why is mass a scalar quantity?
→ Mass does not have direction, only magnitude, so it is a scalar quantity.
9. Why is weight a vector quantity?
→ Weight has both magnitude and direction (towards the center of the Earth).
10. What is the standard unit of length in the metric system?
→ The standard unit of length is meter (m).
11. What are the MKS and CGS systems?
→ MKS system uses meters, kilograms, and seconds, while CGS system uses centimeters, grams, and seconds.
12. Why do we need standard units of measurement?
→ Standard units ensure that measurements are accurate and uniform worldwide.
13. What is velocity?
→ Velocity is speed with direction, measured in meters per second (m/s).
14. What is density?
→ Density is the mass per unit volume of a substance, measured in kg/m³.
15. What device is used to measure time accurately?
→ The atomic clock is used to measure time most accurately.
Long Questions
1. Why is the weight of an object different on different planets?
→ Weight depends on gravity, which is different on each planet. A person’s weight is less on the Moon than on Earth because the Moon’s gravity is weaker.
2. What precautions should we take for accurate measurements?
→ We should use standard measuring devices, check for zero error, and measure on a stable surface to avoid mistakes.
3. What is the difference between mass and weight?
→ Mass is the amount of matter in an object and remains constant, while weight depends on gravity and changes from place to place.
4. What is a scalar quantity? Give an example.
→ A scalar quantity has only magnitude (size) but no direction. Example: Temperature is 30°C (it has a value but no direction).
5. What is a vector quantity? Give an example.
→ A vector quantity has both magnitude and direction. Example: A car moving 50 km/h towards the north.
6. Why should we not use body parts for measurement?
→ Body parts vary in size from person to person, leading to inaccurate measurements. That’s why we use standard units like meters and kilograms.
7. Why is it important to standardize weights and measures?
→ Standardization ensures fair trade, accurate science experiments, and consistency in measurements across the world.
8. What is the importance of accurate measurement in daily life?
→ Accurate measurement helps in buying groceries, cooking, construction, scientific research, and medicine, ensuring correct usage of materials.
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