Measurement And Measuring Instruments

We know that 1km = 10³ m = 10⁵ cm = 10⁶ mm

So, mm < cm < m < km.

Metre is a unit of length and rulers, metre scales and measuring tapes are used to measure length.

1 metric ton = 1000 kg and 1 quintal = 100 kg

So, 1 metric ton = 10 quintals.

Chennai and Kanyakumari are two cities and distance between them is large. So, it is measured in kilometres.

Spring balance is used to measure weight not mass.

We can find the thickness of a hollow tea cup by using screw gauge. To find the thickness of the cup, follow given steps:

i) Determine the least count, pitch and the zero error of the screw gauge.

ii) Hold the cup between anvil and spindle.

iii) Rotate the head until the cup is held firmly but not tightly, with the help of the ratchat .

iv) ) Note the reading of the pitch scale crossed by the head scale (PSR) and the head scale division that coincides with the pitch scale axis (HSC).

v) The thickness of the cup is given by PSR + CHSR (Corrected HSR). Repeat the experiment for different positions of the coin.

vi) Note the readings in a table.

vii) The average of the last column readings gives the thickness of the cup.

We can find the thickness of a one rupee coin by using a screw gauge. It can be done in following steps:

i) Determine the pitch, the least count and the zero error of the screw gauge.

ii) Place the coin between the two studs.

iii) Rotate the head until the coin is held firmly but not tightly, with the help of the ratchat .

iv) Note the reading of the pitch scale crossed by the head scale (PSR) and the head scale division that coincides with the pitch scale axis (HSC).

v) The width of the coin is given by PSR + CHSR (Corrected HSR). Repeat the experiment for different positions of the coin.

vi) Tabulate the readings.

vii) The average of the last column readings gives the thickness of the coin.

i) ACCURATE

ii) VERNIER

iii) KELVIN

iv) NEWTON

v) LEAST COUNT

vi) PITCH

vii) ERROR

viii) BEAM

ix) SCREW

x) CONSTANT

Unit of mass is kg and unit of volume is m³. So Unit of Density is kgm^-3.

Unit of distance is m and unit of time is s. So unit of velocity is ms^-1.

Change in velocity has unit ms^-1 and time has unit s. So unit of acceleration is ms^-2.

Unit of mass is kg and unit of acceleration is ms^-2. So Unit of Force in fundamental quantities is kgms^-2.

Unit of force is kgms^-2 and unit of area is m². So unit of pressure is kgm^-1s^-2.

Metre is the unit of length.

Explanation: Metre is the SI unit of Length.

1 kg of rice is weighed by beam balance.

Explanation:

A beam balance compares the sample mass with a standard reference mass. Standard reference masses are 5g, 10g, 20g, 50g, 100g, 200g, 500g, 1kg, 2kg, 5kg. So it is used to measure 1 kg of rice.

The thickness of a cricket ball is measured by vernier scale.

Explanation:

The diameters of spherical objects such as cricket ball and hollow objects such as a pen cap cannot be measured with a meter scale. For this purpose, we use vernier scale to measure inner and outer diameter.

The radius of a thin wire is measured by screw gauge.

Explanation: Radius of a thin wire is very small to measure. It can’t be measured by metre scale or vernier scale. But screw gauge can measure upto 0.01 mm. So, it is used for measuring radius of a thin wire.

A physical balance measures small differences in mass up to milligram.

Explanation: Physical balance is very sensitive and used in labs for measuring. It is similar to beam balance. It can measure correctly up to milligram.

False

Explanation: Kilogram is unit of mass and electric current is measured in ampere.

True

Explanation: Kilogram is SI unit of mass.

True

Explanation: In day-to-day life, we generally ask for the weight of a substance.

True

Explanation: Physical balance is very sensitive and used in labs for measuring. It is similar to beam balance. It can measure small differences in mass up to milligram.

True

Explanation: Zero degree Celsius is equal to 273.15 K and 1 degree Celsius is equal to interval of 1 K.

1 degree Celsius = 273.15 K + 1 K = 274.15 K

Hint: Based on SI unit of measurement.

SI unit of length is metre.

SI unit of mass is kilogram.

SI unit of time is second.

SI unit of temperature is Kelvin.

Hint: Based on things measured by devices.

Thickness of coins can be measured by using screw gauge.

Diameter of cricket ball can be measured by using vernier caliper.

Mass of vegetables can be measured by using beam balance.

Mass of Gold can be measured by using Digital balance.

Hint: Based on measuring devices and physical quantities.

Temperature can be measured by using Thermometer.

Mass can be measured by using Beam Balance.

Length can be measured by using Ruler.

Time can be measured by using Digital clock.

Here, R is not giving proper reason that how SI system of units is the improved system of units of measurement. SI unit system is improved system as it has fixed reference and accepted in all over the world.

Estimating a value makes calculation easy.

When we’re purchasing tickets for a group of people or splitting

the cost of dinner between 8 friends, we estimate for ease and to

save our time from more complex calculation.

Reason behind assertion is “Kilogram is SI unit of mass”. So, for correct scientific expression, mass of the bag is 10 kg.

We add 273 to temperature in Celsius to convert it into the Kelvin scale. Therefore, 0 ^ο c = 0+273 K = 273 K.

The distance between two celestial bodies is measured in the unit of light year because these bodies are very far from each other and light year is larger unit for measuring length.

1 metric ton = 10 quintals and 1 quintal = 100 kg

Therefore, 1 metric ton = 10 × 100 = 1000 kg

Weight of a tablet is very less. So, it is measured in milligrams (mg).

Measurement is the assignment of a number to a characteristic of an object or event which can be compared with other objects or events. It is determination of the size or magnitude of something.

A standard unit is a reference point by which objects of weight, length, or capacity can be described. Reference point will be fixed everywhere and will not change from person to person or place to place.

Full form of SI system is International System of Units.

The smallest value that can be measured by the measuring device is called its least count.

Pitch of screw gauge is equal to the distance travelled by the tip of the screw for one complete rotation of the head.

Yes. But it will not be much accurate as least count of my ruler is 1 mm.

Rules that are followed in writing the symbols of units in SI system are:

i) The symbols of the units named after scientists should be written by the initial capital letter. E.g. N for newton, H for henry, A for ampere and W for watt.

ii) Small letters are used as symbols for units not derived from a proper noun. E.g. m for metre, kg for kilogram.

iii) No full stop or other punctuation marks should be used within or at the end of symbols. E.g. 50 m and not as 50 m.

iv) The symbols of the units are not expressed in plural form. E.g. 10 kg not as kgs.

v) Use of solidus is recommended for indicating a division of one unit symbol by another unit symbol. Not more than one solidus is used. E.g. ms^-1 or m/s. J/K/mol should be JK^-1 mol^-1

vi) Accepted symbols alone should be used. E.g. ampere should not be written as amp and second should not be written as sec.

Standard unit is needed due to following reasons:

i) We needed to have fixed reference for measurement so that it doesn’t change from person to person.

ii) People in the different parts of the world were using different units which make the exchange of things difficult due to different units.

iii) We need units that will be accepted worldwide for ease of exchange and communication.

Thickness of a plastic carry bag can be measured in micrometre because plastic bags are very thin and can be measured by using screw gauge.

Least count of vernier caliper can be measured by following steps:

i) Find main scale division. The main scale division can easily

be obtained by inspecting the main scale. It will be in centimetre, further divided into millimetre. The value of smallest main scale division is 1 mm.

ii) Then find the vernier scale division. The Vernier scale division is obtained by counting number of division in it. In the Vernier scale there will be 10 divisions.

iii) To obtain least count, divide the smallest main scale division by total number of vernier scale division.

Speed of Light = 3 × 10⁸ ms^-1

Seconds in 1 year = 365 × 24 × 60 × 60

= 3.153 × 10⁷ seconds

Total distance in 1 light year = speed × time

= 3 × 10⁸ × 3.153 × 10⁷

= 9.46 × 10¹⁵ m

1 m = 10^-3 km

9.46 × 10¹⁵ m = 9.46 × 10¹² km

Therefore, Inian and Ezhilan both are right.

Here, thickness of the rubber ball = diameter of the ball.

Main scale reading = 7 cm

Vernier scale reading = 6

Least count = 0.01 cm

Assuming, there is no zero error

Diameter of the ball =

Main scale reading (MSR) +

(Vernier scale coincidence (VC) × least count (LC)) ± ZE

= 7 + (6 × 0.01) ± 0

= 7.06 cm

Radius of ball

= 3.53 cm

Hence, radius of the ball is 3.53 cm.

Given, Pitch scale reading (PSR) = 1 mm

Head scale coincidence (HSC) = 68

Least count (LC) = 0.01 mm

Assuming no zero error, we get

Corrected Head scale coincidence (CHSC) = 68

Thickness of the coin = PSR + (CHSC × LC)

= 1 + (68 × 0.01) mm

= 1.68 mm

Hence, Thickness of the coin is 1.68 mm.

weight = mass × gravity

We know that, gravity = 9.8 ms^-2

Given, weight = 98 N

= 10 kg

Hence, mass of the object is 10 kg.