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Notes Science Grade 8 Physical Quantity Unit 8 Questions and Answers

        Physical Quantity     Chapter # 8    Grade 8

1. What is meant by physical quantities?

Ans: The quantities which can be measured are called Physical Quantities.

2. Write some physical quantities?

Ans: Length, mass, time, etc are some physical quantities.

3. How many things are common in physical quantities?

Ans:Physical quantities have at least two things in common.

4. Write the things that are common in physical quantities?

Ans: One is the size or magnitude and the other is unit.

5. What is meant by unit?  

Ans: There is a need of some standard quantity for measuring unknown quantity. This standard quantity is called unit.

6. Who face the problem of converting units before the international/ System of unit?

Ans: People especially business communities and scientists of different countries faced the problems of converting the units.

7. Define SI unit?

Ans: In 1960, the eleventh general conference of the international committee on weights and measures recommended that all countries of the world should adopt a same kind of standard units. This conference was held in Paris. This conference recommended the use of an international system of units. It is abbreviated as SI.

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8. Write the units of Length, Mass, Time, and volume?

Physical quantity

 Symbol

Unit

Symbol

Length

    l

Meter

m

Mass

       m

Kilogram

kg

Time

    t

Second

s

Volume

       V

Cubic meter

m 3

   

1m

100cm           

1cm

10mm

1km

1000m

1mm

10-3m

1cm

10-2m

1m

10-3km

1kg

1000g

1g

1000mg

1mg

10-3 g

1g

10-3 kg

1ms

10-3 s

1µs

10-6s

Units

Symbol

Multiples

Axa

E

1018

Peta

P

1015

Tera

T

1012

Giga

G

109

Mega

M

106

Kilo

K

103

Hecta

H

102

Deca

Da

101

Deci

D

10-1

Centi

C

10-2

Milli

M

10-3

Micro

µ

10-6

Nano

N

Pico

P

Femto

F

Atto

A

1dm3

1L,1000ml

1000ml

1000cm3

1ml

1cm3

9. What is liter?

Ans: A the practical unit of volume is liter.

 10. Whom the liter mostly used?

Ans: The liter is mostly used to measure liquids such as petrol, milk and cooking oil, etc.

11. Whom the prefixes are based on?

Ans:Prefixes are based on multiplying and dividing the units by power of 10.

12. Define Prefixes?

Ans: The word or letters added before SI units are called prefixes.

13. Give some examples of prefixes?

Ans: Mille, Centi and Kilo etc are examples of prefixes.

14. Give multiples and sub-multiples of length?

 15. Name some multiples and sub-multiples of mass?

 16. Write sub-multiples of time?

 17. Write some names of units?

 18. What are measuring instruments?

Ans: Measuring instruments are used to measure various Physical quantities.

19. How many types of measuring instruments?

Ans: There are four types of measuring instruments.

(1) Meter Rule (2) Flasks    (3) Measuring cylinder   (4) Pipette

20. What is the meter rule?

Ans: A meter the rule is one meter long graduated stick. It is usually used to measure the length of an object or distance between two points.

21. In how many parts a meter rule is divided?

Ans: A meter the rule is divided into 100 equal parts.

22. Write the method to measure the length of a meter rule?

Ans: Eye must be kept vertically above the reading point. If the eye is positioned either left or right to the reading point, the reading becomes doubtful.

23. What is the correct way to read meniscus?

Ans: The way to read the meniscus is to position the eye at the same level as the meniscus.

24. Define Measuring cylinder?

Ans: A measuring cylinder is used to measure the volume of a liquid.

25. Why the measuring cylinder is called the measuring cylinder?

Ans: It has a scale in milliliter (ml) or cubic centimeter along its length. That is why it is called the graduated cylinder.

26. Write the method to measure the volume by measuring cylinder?

Ans: To measure the correct volume of a liquid, the cylinder must be placed on horizontal surface and eyes should be kept on the level with the bottom of the meniscus.

27. What is the difference between meniscus of liquid and mercury?

Ans: The meniscus of most of the liquids curves downwards whereas the meniscus of mercury curves upward.

 28. Name the multiples and sub-multiples of liters?

29. Write the formula of an irregular-shaped object?

Ans: The formula of an irregular shaped object is given below:

 V=   V2 – V1

30. What is meant by flask?

Ans: Flasks are laboratory vessels. They are made of glass and plastics. They are available in many shapes and sizes.

31. In how many sizes the flasks are available in school laboratory?

Ans: These are usually available in the sizes of 50ml, 100ml, 250ml, 500ml, and 1000ml.

32. Give use of flasks?

Ans: Flasks are used for making solutions.

33. Write the units of flasks?

Ans: These are graduated in units of a cubic centimeter or Mille litters.

34. Define Pipette?

Ans: Pipettes are commonly used in chemistry and biology laboratories.

35. Where the pipettes are commonly used?

Ans:  It is used to measure the volume.

36. In how many sizes the pipette available?

Ans: They are available in the size of 10ml to 25ml.

37. Write the objects used to make the pipette?

Ans: Pipettes are made of glass or plastic.

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