Measurement | Unit-1 | Lesson 1 | Science Notes | Class 6

5. Differentiate between:

a. MKS and CGS systems.

Answer: The difference between MKS and CGS System are:-

MKS System	CGS System
1. In MKS System, the length is measured in metre, mass in kilogram and time in second.	1. In CGS System, the length is measured in centimeter, mass in gram and time in second.
2. MKS System is also called metric system.	2. CGS System is known as the French System of units.
3. In measuring force, MKS system using Newtons as the unit is widely accepted worldwide.	3. In measuring force, CGS system using dyne as the unit is seldom used.
4. In measuring volume of liquids and solids, the liter and the cubic meters are always used.	4. In measuring volume of liquids and solids, the liter and the cubic centimeters are or cc is less used.
5. The MKS System is more popular than CGS System.	5. The CGS System is less popular.

#What are the differences between MKS System and CGS System?

b. kilogram and kilometre

Answer: The difference between kilogram and kilometre are-

6. Give reasons.

a. SI units are used for the scientific measurement.

Answer: SI units are used for the scientific measurement to avoid confusion when measuring among the scientists all over the world.
Or,
SI unit is used in most places around the world, so our use of it allows scientist from desperate regions to use a single standard unit in communicating scientific data without vocabulary confusion.
#Why SI units are used for the scientific measurement?

b. We need standard units to measure the physical quantity.

Answer: We need standard units to measure the physical quantity because it helps to maintain uniformity about measurement throughout the world.

7. Answer the following questions.

a. Define a physical quantity. Write the SI units of mass, length and time.

Answer: The quantity which can be measured are called physical quantity. The SI units of mass is kilogram (kg), length is meter (m) and time is second (s).
#What do you mean by physical quantity?

b. Define measurement and the SI system of units.

Answer: Measurement is the process of comparing an unknown physical quantity with a standard known quantity.

The system of units recommended by the International Convention of Scientists held in France is known as the SI system of units. In SI system of units, mass is measured in kilogram (kg), length in meter (m), time in second (s) and temperature in Kelvin (k).

#What do you mean by measurement? What is SI system of units?

c. What is a standard unit?

Answer: The unit of measurement which is accepted all over the world as a basic unit is called a Standard unit.

d. Define mass and write it's units.

Answer: The amount of matter contained in a body is called mass. The units of mass are gram, kilogram, quintal and metric ton.
#What do you mean by mass?

e. Define CGS and FPS systems.

Answer: The system of units in which length is measured in centimeter (cm), mass in gram (g) and time in second (s) is called CGS system.

The system of units in which length is measured in foot (ft), mass in pound (lb) and time in second (s) is called FPS system.
#What is CGS System? #What is FPS system?

f. What precautions should be taken while measuring length?

Answer: The precautions should be taken while measuring length are as follows:

1. The scale should be kept parallel to the measuring side.
2. If the edge of the scale is damaged, 0 'zero' of the scale can't be taken as the reference point. So, another whole number such as 1,2,3... can be taken as the reference point.
3. Sometimes, the scale may be defective. In such situation, we should take the average length.
4. Our eyes should be fixed vertically above the scale so that the end of the surface coincides with the reference of the scales. Otherwise errors may arise.

g. What things should we remember while writing the symbols of units?

Answer: We should remember below things while writing the symbols of units:

1. A period (.) should not be used after or between the symbols except the symbol is at the end of the sentence. [A pencil is 15 cm. long. ✕] - [A pencil is 15 cm long.✓]
2. The unit should not be expressed in the plural form. [Nischal can carry 5 kgs rice. ✕] - [Nischal can carry 5 kg rice.✓]
3. No space should be left between a prefix and the main unit. [millimetre → m m ✕] - [millimetre → mm ✓]
4. A space should be left between the symbol of a unit, if the unit is made up of two or more units. [metre per second → ms - 1✕] - [metre per second → ms-1✓]

h. Write any two disadvantages of the use of local units.

Answer: The two disadvantages of the use of local units are:-
1. With local units such as haat or cubit, bitta, foot, etc in measuring length, it is not reliable and accurate because it varies/differs from person to person.
2. With local units such as mana, pathi, muri, dharni, pau, etc in measuring the mass of a substance, it is not reliable and accurate because it varies/differs from place to place.

i. Write the importance of measurement.

Answer: The importance of measurement in our daily life are mentioned below:
1. Measurement is useful for selling and buying goods.
2. Measurement is essential for making and preparing food.
3. Measurement is important for conducting scientific experiments.
4. Measurement is important for global understanding of the quantity of substances.
5. Measurement is useful to measure raw materials in industries, etc.

j. Mass can be measured in local units like dharni, pau, etc. Discuss the advantages of using standard units of mass over the local units of mass.

Answer: _____

k. Write the full form of MKS and FPS.

Answer:
The full form of MKS is Metre, Kilogram and Second.
The full form of FPS is Foot, Pound and Second.

8. What is the diameter of the marble in the given diagram?

_____

9. Numerical problems:

a. Convert the following:

i. 50 cm into m
Solution:
= 50/100 m [∵ cm 10 dm 10 m = i.e. to change cm to m, we need to divide by 100 (10x10)]
= 0.5 m

ii. 6 kg into g
Solution:
= 6 x 1,000 g [∵ g 10 dag 10 hg 10 kg = i.e. to change kg to g, we need to multiply by 1,000 (10x10x10)]
= 6,000 g

iii. 40s into min
Solution:
= 40/60 min [∵ s 60 min = i.e. to change s to min, we need to divide by 60]
= 0.67 min

iv. 2 km into cm
Solution:
= 2 x 100000 cm [∵ km 10 hm 10 dam 10 m 10 dm 10 cm = i.e. to change km to cm, we need to multiply by 1,00,000 (10x10x10x10x10)]
= 2,00,000 cm

v. 4.5 kg into g
Solution:
= 4.5 x 1000 g [∵ kg 10 hg 10 dag 10 g = i.e. to change kg to g, we need to multiply by 1,000 (10x10x10)]
= 4,500 g

vi. 100 min into s
Solution:
= 100 x 60 s [∵ min 60 s = i.e. to change min to s, we need to multiply by 60]
= 6,000 s

vii. 665 hr into s
Solution:
= 665 x 3,600 s [∵ hr 60 min 60 s = i.e. to change hr to s, we need to multiply by 3,600 (60x60)]
= 23,94,000 s

viii. 560 hr into days
Solution:
= 560/24 days [∵ hr 24 days = i.e. to change hr to days, we need to divide by 24]
= 23.33 days

ix. 20 g into kg
Solution:
= 20/1000 kg [∵ g 10 dag 10 hg 10 kg = i.e. to change g to kg, we need to divide by 1,000 (10x10x10)]
= 0.02 kg

x. 20 mm into m
Solution:
= 20/1,000 m [∵ mm 10 cm 10 dm 10 m = i.e. to change mm to m, we need to divide by 1,000 (10x10x10)]
= 0.02 m

xi. 365 days into s
Solution:
= 365 x 86,400 s [∵ day 24 hr 60 min 60 s = i.e. to change days into s, we need to multiply by 86,400 (24x60x60)]
= 3,15,36,000 s