## Samacheer Kalvi 9th Term I Science Book Back Question and Answers – Unit 1:

Samacheer Kalvi 9th Standard New Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 9 New Syllabus 2021 to 2022 Book Back Ques & Ans solutions available for both English and Tamil Medium. Class 9 Science Book Term 1 Unit 1 – Measurement and Measuring Instrument Answers/Solutions are provided on this page. 9th Std Science Book is of Term 1st, 2nd, 3rd, and consists of 9 Units in each Term. All 9 Units of Term 1st, 2nd, 3rd Science Book Back One, and Two Mark Solutions are given below.

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### Samacheer Kalvi 9th Science Book Back Unit 1 Term 1 Solutions Guide PDF:

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### Measurement and Measuring Instrument – Book Back Answers

I. Multiple Choice Questions

1. Choose the correct one
a. mm< cm < m < km
b. mm > cm > m > km
c. km < m < cm < mm
d. mm > m> cm> km

2. Rulers, measuring tapes and metre scales are used to measure
a. Mass
b. Weight
c. Time
d. Length

3. 1 metric ton is equal to
a. 100 quintals
b. 10 quintals
c. 1/10 quintals
d. 1/100 quintals

4. Distance between Chennai and Kanyakumari can be found in
a. Kilometres
b. Metres
c. Centimetres
d. Millimetres

5. Which among the following is not a device to measure mass?
a. Spring balance
b. Beam balance
c. Physical balance
d. Digital balance

II. Fill in the blanks

1. Metre is the unit of Length
2. 1 kg of rice is weighed by Common Beam balance
3. The thickness of a cricket ball is measured by Vernier caliper
4. The radius of a thin wire is measured by Screw guage
5. A physical balance measures small differences in mass up to 1 Milligram

III. True or False

1. The SI unit of electric current is kilogram – False
2. Kilometre is one of the SI units of measurement – False
3. In everyday life, we use the term weight instead of mass. – True
4. A physical balance is more sensitive than a beam balance as it can accurately measure even a very small mass, even milligram – True
5. One Celsius degree is an interval of 1K and zero degree Celsius is 273.15 K. – True

IV. Match the following

1. Column I                Column II
i)  Length                  a) Kelvin
ii) Mass                     b) metre
iii) Time                    c) kilogram
iv) Temperature      d) second

Ans: i – b; ii – c; iii – d; iv – a

2. Column I                     Column II
i) Screw gauge                 a) Vegetables
ii) Vernier caliper           b) Coins
iii) Beam balance            c) Gold ornaments
iv) Digital balance           d) Cricket ball

Ans: i – b; ii – d; iii – a; iv – c

3. Column I                        Column II
i) Temperature                a) Beam balance
ii) Mass                             b) Ruler
iii) Length                        c) Digital clock
iv) Time                            d) Thermometre

Ans: i – d; ii – a; iii – b; iv – c

V. Assertion and reason type

1. Assertion (A): The SI systems of units is the improved system of units for measurement.
Reason (R): The SI unit of mass is kilogram
a. Both A and R are true but R is not the correct reason
b. Both A and R are true and R is the correct reason
c. A is true but R is false
d. A is false but R is true

2. Assertion (A): The skill of estimation is important for all of us in our daily life.
Reason (R): The skill of estimation reduces our consumption of time
a. Both A and R are true but R is not the correct reason
b. Both A and R are true and R is the correct reason
c. A is true but R is false
d. A is false but R is true

3. Assertion(A): The scientifically correct expression is “ The mass of the bag is 10 kg”
Reason (R): In everyday life, we use the term weight instead of mass
a. Both A and R are true but R is not the correct reason
b. Both A and R are true and R is the correct reason
c. A is true but R is false
d. A is false but R is true

4. Assertion (A): 0 °C = 273.16 K. For our convenience we take it as 273 K after rounding off the decimal
Reason (R): To convert a temperature on the Celsius scale you have to add 273 to the given temperature
a. Both A and R are true but R is not the correct reason
b. Both A and R are true and R is the correct reason
c. A is true but R is false
d. A is false but R is true

5. Assertion (A): The distance between two celestial bodies is measured in the unit of light year
Reason (R): The distance travelled by the light in one year is one light year
a. Both A and R are true but R is not the correct reason
b. Both A and R are true and R is the correct reason
c. A is true but R is false
d. A is false but R is true

VI.   Comprehensive Type:

Mass is the amount of matter contained in an object. Measurement of mass helps us to distinguish between lighter and a heavier body. Bean balance, spring balance and electronic balance are used to measure mass of different objects.   The SI unit of mass is the kilogram (kg). But different units are used to measure the mass of different objects depending upon their weight. E.g. Weight (mass) of a table is measured in milligrams (mg), weight of a student is measured in kilogram (kg) and weight of a truck with goods I measured in metric tons. 1 metric ton is equal to 10 quintals and 1 quintal is equal to 100kg. 1 gram is equal to 1000mg.

1. Value of 1 metric ton is equal to
a) 1000kg b) 10 quintals c) 1000,000g               d) 100kg

Ans: a, b and c are true

2. How will you measure weight of a table?
a) kg b) g c) mg d) None of these

Ans: c) mg

1.  Define measurement.
Measurement is the assignment of a number to a characteristic of an object or event which can be compared with other objects or events.

2.  Define standard unit.
SI system of units is the modified and improved form of the previous system of units. It is accepted in almost all the countries of the world.

3.  What is the full form of SI System?
SI System: International System of units.

4.  Define least count of any device.
The smallest length which can be measured by device is called least count.

5.  What do you know about pitch of screw gauge?
The pitch of the screw is the distance between two successive screw threads. It is also equal to the distance travelled by the tip of the screw for one complete rotation of the head.

6.  Can you find the diameter of a thin wire of length 2m using the ruler from your instrument box?
Ans: Yes
Take the wire and wind it around the pencil. Count the number of turns. Now we compress the wire and measure the length of the turns against the ruler.

Diameter = Length of the Turns / No. of turns

1.  Differentiate mass and weight

 Mass Weight Fundamental quantity Derived quantity Has magnitude alone – scalar quantity Has magnitude and direction vector quantity It is the amount of matter contained in body It is the normal force exerted by the surface on the object against gravitational pull Remains the same Varies from place to place

2. What is the measuring unit of the thickness of a plastic carry bag?
The Measuring unit of thickness of a plastic carry bag is micron.

One micron = 10-6 m

3. Write the need of a standard unit
Many of the ancient system of measurement were based on the dimensions of human body. As a result, unit of measurement varied from person to person and also from location to location.
So we need of a standard unit.

4. How will you measure the least count of vernier caliper?