9th Measurement PDF

www.tntextbooks.in UNIT 1 MEASUREMENT Learning Objectives After completing this lesson, students will be able to „„understand the fundamental and derived quantities and...

www.tntextbooks.in UNIT 1 MEASUREMENT Learning Objectives After completing this lesson, students will be able to „„understand the fundamental and derived quantities and their units. „„know the rules to be followed while expressing physical quantities in SI units. „„get familiar with the usage of scientific notations. „„know the characteristics of measuring instruments. „„use vernier caliper and screw gauge for small measurements. „„find the weight of an object using a spring balance. „„know the importance of accurate measurements. Introduction quantities. Quantities which cannot be expressed in terms of any other physical quantities are called Measurement is the basis of all important fundamental quantities. Example: Length, mass, scientific study. It plays an important role in time, temperature etc. Quantities which can be our daily life also. While finding your height, expressed in terms of fundamental quantities are buying milk for your family, timing the race called derived quantities. Example: Area, volume, completed by your friend and so on, you need density etc. to make measurements. Measurement answers questions like, how long, how heavy and how Physical quantities have a numerical fast? Measurement is about assigning a number value and a unit of measurement (say, 3 to a characteristic of an object or event which kilogram). Suppose you are buying 3 kilograms can be compared with other objects or events. of vegetable in a shop. Here, 3 is the numerical It is defined as the determination of the size value and kilogram is the unit. Let us study or magnitude of a quantity. In this lesson you about units now. will learn about units of measurements and the characteristics of measuring instruments. 1.1.2 Units A unit is a standard quantity with which  Physical Quantities the unknown quantities are compared. It is 1.1 and Units defined as a specific magnitude of a physical quantity that has been adopted by law or 1.1.1 Physical quantities convention. For example, feet is the unit for Physical quantity is a quantity that can be measuring length. That means, 10 feet is equal measured. Physical quantities can be classified to 10 times the definite pre-determined length, into two: fundamental quantities and derived called feet. 1 IX_SCI_EM_Unit-01_PHY.indd 1 12/12/2021 3:57:44 PM  www.tntextbooks.in Earlier, different unit systems were used The units used to measure the by people from different countries. Some of the fundamental quantities are called fundamental unit systems followed earlier are given below in units and the units which are used to measure Table 1.1. the derived quantities are called derived units. Table 1.1 Unit systems of earlier times Table 1.2 Fundamental quantities and their units System Length Mass Time Fundamental CGS centimetre gram second Unit Symbol quantities FPS foot* pound second Length metre m MKS metre kilogram second Mass kilogram kg * foot is the singular of feet Time second s At the end of the Second World War Temperature kelvin K there was a necessity to use worldwide system Electric current ampere A of measurement. Hence, SI (International Luminous intensity candela cd System of Units) system of units was developed Amount of substance mole mol and recommended by General Conference on Weights and Measures at Paris in 1960 for With the help of these seven fundamental international usage. units, the units for other derived quantities are obtained and their units are given below in 1.2 SI System of Units Table 1.3. SI system of units is the modernised 1.3 Fundamental Units and improved form of the previous system of units. It is accepted in almost all the countries. 1.3.1 Length It is based on a certain set of fundamental units from which derived units are obtained by proper Length is the extent of something combination. There are seven fundamental units between two points. The SI unit of length is in the SI system of units. They are also known as metre. One metre is the distance travelled by base units and they are given in Table 1.2. light through vacuum in 1/29,97,92,458 second. Table 1.3 Derived quantities and their units S.No Physical quantity Expression Unit 1 Area length × breadth m2 2 Volume area × height m3 3 Density mass / volume kgm–3 4 Velocity displacement / time ms–1 5 Momentum mass × velocity kgms–1 6 Acceleration velocity / time ms–2 7 Force mass × acceleration kgms–2 or N 8 Pressure force / area Nm–2 or Pa 9 Energy (work) force × distance Nm or J 10 Surface tension force / length Nm–1 Measurement 2 IX_SCI_EM_Unit-01_PHY.indd 2 12/12/2021 3:57:44 PM  www.tntextbooks.in In order to measure very large distance The nearest star alpha centauri (distance of astronomical objects) we use the is about 1.34 parsec from the following units. sun. Most of the stars visible to Astronomical unit the unaided eye in the night sky Light year are within 500 parsec distance from the sun. Parsec To measure small distances such as Astronomical unit (AU): It is the mean distance between two atoms in a molecule, distance of the centre of the Sun from the size of the nucleus and wavelength etc. we centre of the Earth. 1 AU = 1.496 × 10 11 m use submultiples of ten. These quantities are (Figure 1.1). measured in Angstrom unit (Table 1.5). Table 1.5 Smaller units Smaller units In metre Fermi (f) * 10–15 m Angstrom (A°)* 10–10 m Nanometre (nm) 10–9 m Micron (micrometre μ m) 10–6 m Millimetre (mm) 10–3 m Centimetre (cm) 10–2 m Figure 1.1 Astronomical unit * Unit outside SI system and still accepted for use. Light year: It is the distance travelled by light in one year in vacuum and it is equal to 9.46 × 1.3.2 Mass 1015 m. Mass is the quantity of matter contained Parsec: Parsec is the unit of distance used to in a body. The SI unit of mass is kilogram (kg). One measure astronomical objects outside the solar kilogram is the mass of a particular international system. prototype cylinder made of platinum-iridium 1 Parsec = 3.26 light year. alloy, kept at the International Bureau of Weights and Measures at Sevres, France. The units gram (g) and milligram (mg) Table 1.4 Larger units are the submultiples of ten (1/10) of the unit kg. Larger units In metre Similarly quintal and metric tonne are multiples of ten (× 10) of the unit kg. Kilometre (km) 103 m 1 g = 1/1000 × 1 kg = 0.001 kg Astronomical unit (AU) 1.496 × 1011 m 1 mg = 1/1000000 × 1 kg = 0.000001 kg Light year (ly) 9.46 × 1015 m 1 quintal = 100 × 1 kg = 100 kg Parsec (pc) 3.08 × 10 m16 1 metric tonne = 1000 × 1 kg = 10 quintal 3 Measurement IX_SCI_EM_Unit-01_PHY.indd 3 12/12/2021 3:57:45 PM  www.tntextbooks.in Atomic mass unit Table 1.6 Unit prefixes Mass of a proton, neutron and electron Power of 10 Prefix Symbol can be determined using atomic mass unit (amu). 1 amu = (1/12)th of the mass of C12 atom. 1015 peta P 1012 tera T More to Know 109 giga G Mass of 1 ml of water = 1g 106 mega M Mass of 1l of water = 1kg 103 kilo k Mass of the other liquids vary with their 102 hecto h density. 101 deca da 1.3.3 Time 10–1 deci d Time is a measure of duration of events 10–2 centi c and the intervals between them. The SI unit of time 10–3 milli m is second. One second is the time required for the 10–6 micro µ light to propagate 29,97,92,458 metres through 10–9 nano n vacuum. It is also defined as 1/86, 400th part of a mean solar day. Larger units for measuring 10–12 pico p time are day, month, year and millennium etc. 10–15 femto f 1 millenium = 3.16 × 109 s. The physical quantities vary in different 1.3.4 Temperature proportion like from 10-15 m being the diameter Temperature is the measure of of nucleus to 1026 m being the distance between hotness or coldness of a body. SI unit of two stars and 9.11 × 10-31 kg being the mass of temperature is kelvin (K). One kelvin is the electron to 2.2 × 1041 kg being the mass of the fraction (1/273.16) of the thermodynamic milky way galaxy. temperature of the triple point of water (The temperature at which saturated water  Rules and Conventions vapour, pure water and melting ice are in 1.5 for writing SI Units equilibrium). Zero kelvin (0 K) is commonly and their Symbols known as absolute zero. The other units for 1. The units named after scientists are not measuring temperature are degree celsius (°C) and fahrenheit (F). written with a capital initial letter. E.g. newton, henry, ampere and watt. 1.4 Unit Prefixes 2. The symbols of the units named after scientists should be written by the initial Unit prefixes are the symbols placed capital letter. E.g. N for newton, H for before the symbol of a unit to specify the order henry, A for ampere and W for watt. of magnitude of the quantity. They are useful to express very large and very small quantities. 3. Small letters are used as symbols for units k (kilo) is the unit prefix in the unit, kilometer. not derived from a proper noun. E.g. m A unit prefix stands for a specific positive or for metre, kg for kilogram. negative power of 10. Some unit prefixes are 4. No full stop or other punctuation given in Table 1.6. marks should be used within or at Measurement 4 IX_SCI_EM_Unit-01_PHY.indd 4 12/12/2021 3:57:45 PM  www.tntextbooks.in the end of symbols. E.g. 50 m and not scale. To the left end of the main scale an upper as 50 m. and a lower jaw are fixed perpendicular to the 5. The symbols of the units are not expressed bar. These are named as fixed jaws. To the right of in plural form. E.g. 10 kg not as 10 kgs. the fixed jaws, a slider with an upper and a lower moveable jaw is fixed. The slider can be moved or 6. When temperature is expressed in kelvin, fixed to any position using a screw. The Vernier the degree sign is omitted. E.g. 283 K not scale is marked on the slider and it moves along as 283° K (If expressed in celsius scale, with the movable jaws and the slider. The lower degree sign should be included e.g. 100°C jaws are used to measure the external dimensions not as 100 C, 108° F not as 108 F). and the upper jaws are used to measure the 7. Use of solidus (/) is recommended for internal dimensions of the objects. The thin bar indicating a division of one unit symbol attached to the right side of the Vernier scale is by another unit symbol. Not more than used to measure the depth of hollow objects. one solidus is used. E.g. ms-1 or m/s. Inside J/K/mol should be JK-1mol-1. Jaws Main Scale 8. The number and units should be separated 0 1 2 3 4 5 6 by a space. E.g. 15 kgms–1 not as 15 kgms–1. 9. Accepted symbols alone should be used. Vernier Scale E.g. ampere should not be written as amp and second should not be written as sec. Object 10. The numerical values of physical Outside quantities should be written in Jaws scientific form. E.g. the density Figure 1.2 Vernier Caliper of mercury should be written as 1.36 × 104 kgm-3 not as 13600 kgm-3. 1.6.2 Usage of Vernier caliper The first step in using the Vernier caliper  ernier Caliper and V is to find out its least count, range and zero error. 1.6 Screw Gauge a) Least count In our daily life, we use metre scale Least count of the instrument (L.C) for measuring lengths. They are calibrated in   Value of one main scale division cm and mm. The smallest length which can = Total number of vernier scale division be measured by metre scale is called least count. Usually the least count of a scale is The main scale division will be in 1 mm. We can measure the length of objects centimeter, further divided into millimetre. The upto 1 mm accuracy with this scale. By using value of the smallest main scale division is 1 mm. vernier caliper we can have an accuracy of In the Vernier scale there will be 10 divisions. 0.1 mm and with screw gauge we can have an 1mm accuracy of 0.01 mm.  L.C   0.1mm = 0.01cm 10 1.6.1 Description of Vernier caliper b) Zero error The Vernier caliper consists of a thin long Unscrew the slider and move it to the steel scale graduated in cm and mm called main left, such that both the jaws touch each other. 5 Measurement IX_SCI_EM_Unit-01_PHY.indd 5 12/12/2021 3:57:47 PM  www.tntextbooks.in Check whether the zero marking of the main left of the zero of the main scale. So, the obtained scale coincides with that of the zero of the vernier reading will be less than the actual reading. To scale. If they coincide then there is no zero error. correct this error we should first find which If they do not coincide with each other, the vernier division is coinciding with any of the instrument is said to possess zero error. Zero main scale divisions, as we found in the previous error may be positive or negative. If the zero of case. In this case, you can see that sixth line is a vernier is shifted to the right of main scale, it coinciding. To find the negative error, we can is called positive error. On the other hand, if the count backward (from 10). Here, the fourth line is zero of the vernier is shifted to the left of the zero coinciding. Therefore, negative zero error = –4 × of main scale, then the error is negative. LC = –4 × 0.01 = –0.04 cm. Then zero correction is positive. Hence, zero correction is +0.04 cm. Positive zero error Figure 1.3 shows the positive zero error. From the figure you can see that zero of the vernier scale is shifted to the right of the zero of the main scale. In this case the reading will be more than the actual reading. Hence, this error should be corrected. In order to correct this error, find out which vernier division is coinciding with Figure 1.4 Negative zero error any of the main scale divisions. Here, fifth vernier division is coinciding with a main scale division. Problem 2 So, positive zero error = +5 × LC = +5 × 0.01 The main scale reading is 8 cm and vernier = 0.05 cm and the zero correction is negative. coincidence is 4 and negative zero error is Hence, zero correction is –0.05 cm. 0.02 cm. Then calculate the correct reading: Solution: Correct reading = 8 cm + (4 × 0.01 cm) + (0.02 cm) = 8+0.04+0.02 = 8.06 cm. We can use Vernier caliper to find different dimensions of any familiar object. If the length, width and height of the object can be measured, Figure 1.3 Positive zero error volume can be calculated. For example, if we could measure the inner diameter of a beaker Problem 1 (using appropriate jaws) as well as its depth Calculate the correct reading, if the main (using the depth probe) we can calculate its inner scale reading is 8 cm, vernier coincidence is 4 volume. and positive zero error is 0.05 cm. Activity 1 Solution: Correct reading = 8 cm + (4 × 0.01cm) – 0.05 cm Using Vernier caliper find the outer diameter = 8 + 0.04 – 0.05 = 8 – 0.01 = 7.99 cm of your pen cap. Negative zero error Now look at the Figure 1.4. You can see that the zero of the vernier scale is shifted to the Measurement 6 IX_SCI_EM_Unit-01_PHY.indd 6 12/12/2021 3:57:48 PM  www.tntextbooks.in 1.6.3 Digital Vernier caliper The end of the screw has a plane surface We are living in a digital world and (Spindle). A stud (Anvil) is attached to the other the digital version of the vernier callipers are end of the frame, just opposite to the tip of the available nowadays. Digital Vernier caliper screw. The screw head is provided with a ratchat (Figure 1.5) has a digital display on the slider, arrangement (safety device) to prevent the user which calculates and displays the measured from exerting undue pressure. value. The user need not manually calculate the 1.7.2 Using the screw gauge least count, zero error etc. The screw gauge works on the principal that when a screw rotates in a nut, the distance moved by the tip of the screw is directly proportional to the number of rotations. a) Pitch of the screw The pitch of the screw Figure 1.5 Digital Vernier caliper is the distance moved by 1.7 Screw Gauge the tip of the screw for one complete rotation of the head. Screw gauge is an instrument that It is equal to 1 mm in typical screw gauges. can measure the dimensions upto 1/100th of a millimetre or 0.01 mm. With the screw gauge Distance moved by the Pitch Pitch of the screw = it is possible to measure the diameter of a thin No. of rotations by Head scale wire and thickness of thin metallic plates. b) Least count of a screw gauge 1.7.1 Description of screw gauge The distance moved by the tip of the The screw gauge consists of a U shaped screw for a rotation of one division on the head metal frame. A hollow cylinder is attached to scale is called the least count of the screw gauge. one end of the frame. Grooves are cut on the inner surface of the cylinder through which a Least count of the instrument (L.C.) screw passes (Figure 1.6). On the cylinder Value of one smallest pitch scale reading = parallel to the axis of the screw there is a scale Total number of Head scale division which is graduated in millimetre. It is called Pitch Scale (PS). One end of the screw is attached LC = 1 = 0.01 mm 100 to a sleeve. The head of the sleeve (Thimble) is divided into 100 divisions and it is called the c) Zero Error of a screw gauge Head scale. When the movable stud of the screw and the opposite fixed stud on the frame area brought into contact, if the zero of the head scale coincides with the pitch scale axis there is no zero error. Positive zero error When the movable stud of the screw and the opposite fixed stud on the frame are brought into contact, if the zero of the head scale Figure 1.6 Screw gauge lies below the pitch scale axis, the zero error is 7 Measurement IX_SCI_EM_Unit-01_PHY.indd 7 12/12/2021 3:57:49 PM  www.tntextbooks.in positive (Figure 1.7). Here, the 5th division of 1.8 Measuring Mass the head scale coincides with the pitch scale axis. Then the zero error is positive and is given by, We commonly use the term ‘weight’ which is actually the ‘mass’. Many things are Z.E = + (n × LC) where ‘n’ is the head measured in terms of ‘mass’ in the commercial scale coincidence. In this case, Zero error world. The SI unit of mass is kilogram (kg). = + (5 × 0.01) = 0.05mm. So the zero correction In any case, the units are based on the items is – 0.05 mm. purchased. For example, we buy gold in gram or milligram, medicines in milligram, provisions in gram and kilogram and express cargo in tonnes. Can we use the same instrument for measuring the above listed items? Different measuring devices have to be used for items of Figure 1.7 Positive Zero Error smaller and larger masses. In this section we will study about some of the instruments used for Negative zero error measuring mass. When the plane surface of the screw and the opposite plane stud on the The shell of an egg is 12% of its frame are brought into contact, if the zero mass. A blue whale can weigh as of the head scale lies above the pitch scale much as 30 elephants and it is as axis, the zero error is negative (Figure 1.8). long as 3 large tour buses. Here, the 95th division coincides with the pitch scale axis. Then the zero error is negative and is Common (beam) balance given by, A beam balance compares the sample ZE = – (100 – n) × LC mass with a standard reference mass (Standard ZE = – (100 – 95) × LC reference masses are 5g, 10g, 20g, 50g, 100g, = – 5 × 0.01 200g, 500g, 1kg, 2kg, 5kg). This balance can = – 0.05 mm measure mass accurately up to 5g (Figure 1.9). The zero correction is + 0.05mm. Figure 1.8 Negative Zero Error Figure 1.9 Common beam balance Activity 2 Physical balance This balance is used in labs and is similar Determine the thickness of a single sheet to the beam balance but it is a lot more sensitive of your science textbook with the help of a and can measure mass of an object correct to a Screw gauge. milligram (Figure 1.10). Measurement 8 IX_SCI_EM_Unit-01_PHY.indd 8 12/12/2021 3:57:49 PM  www.tntextbooks.in The standard reference masses used in attached to the rod which slides over a graduated this physical balance are 10 mg, 20 mg, 50 mg, scale on the right. The spring extends according 100 mg, 200 mg, 500 mg, 1 g, 2g, 5 g, 10 g, 20 g, to the weight attached to the hook and the pointer 50 g, 100g, and 200 g. reads the weight of the object on the scale. Figure 1.12 Spring balance Figure 1.10 Physical balance 1.8.1 Difference between mass and weight Digital balance Mass (m) is the quantity of matter Nowadays, for accurate measurements contained in a body. Weight (w) is the normal digital balances are used, which measure mass force (N) exerted by the surface on the body accurately even up to a few milligrams, the least to balance against gravitational pull on the value being 10 mg (Figure 1.11). This electrical object. In the case of spring scale, the tension device is easy to handle and commonly used in in the spring balances the gravitational pull jewellery shops and labs. on the object. When a man is standing on the surface of the earth or floor, the surface exerts a normal force on the body which is equivalent to gravitational force. The gravitational force acting on the object is given by ‘mg’. Here, m is mass of the object and ‘g’ is acceleration due to gravity. Problem 3 If a man has a mass 50 kg on the earth, then Figure 1.11 Digital balance what is his weight? Activity 3 Solution: Weight (w) = mg With the resources such as paper plates, tea Mass of a man = 50 kg cups, thread and sticks available at home His weight = 50 × 9.8 make a model of an ordinary balance. Using w = 490 newton standard masses find the mass of some objects. The pull of gravity on the Moon is 1/6 Spring balance times weaker than that on the Earth. This causes This balance helps us to find the weight of the weight of the object on the Moon to be less an object. It consists of a spring fixed at one end and than that on the Earth by six times. Acceleration a hook attached to a rod at the other end. It works due to gravity on the Moon = 1.63 ms–2 by ‘Hooke’s law’ which states that the addition of If the mass of a man is 70 kg then his weight produces a proportional increase in the weight on the Earth is 686 N and on the Moon length of the spring (Figure 1.12). A pointer is is 114 N. But his mass is still 70 kg on the Moon. 9 Measurement IX_SCI_EM_Unit-01_PHY.indd 9 12/12/2021 3:57:50 PM  www.tntextbooks.in Mass Weight 1. It is a fundamental quantity. It is a derived quantity. 2. It has magnitude alone – scalar quantity. It has magnitude and direction – vector quantity. 3. It is the amount of matter contained in a It is the normal force exerted by the surface on body. the object against gravitational pull. 4. Remains the same everywhere. Varies from place to place. 5. It is measured using physical balance. It is measured using spring balance. 6. Its unit is kilogram. Its unit is newton.  Accuracy in called derived quantities. Example: Area, 1.9 Measurements volume and density etc. ™™A unit is the fundamental quantity with When measuring physical quantities, which unknown quantities are compared. accuracy is important. Accuracy represents ™™Length, mass, time, temperature, electric how close a measurement comes to a true current, intensity and mole are the value. Accuracy in measurement is center fundamental units in SI system. in engineering, physics and all branches of ™™To find the length or thickness of smaller science. It is also important in our daily life. dimensions Vernier caliper and Screw You might have seen in jewellery shops how gauge are used. accurately they measure gold. What will happen if little more salt is added to food while ™™Austronomical unit is the mean distance cooking? So, it is important to be accurate of the Sun from the center of the Earth. when taking measurements. 1AU=1.496 × 1011m. Faulty instruments and human error ™™Light year is the distance travelled can lead to inaccurate values. In order to get by light in one year in vacuum. accurate values of measurement, it is always 1 Light year = 9.46 × 1015m. important to check the correctness of the ™™Parsec is the unit of distance used to measuring instruments. Also, repeating the measure astronomical objects outside the measurement and getting the average value solar system. can correct the errors and give us accurate ™™1 Angstrom (A°) = 10−10 m. value of the measured quantity. ™™SI Unit of volume is cubic metre or m3. Points to Remember Generally volume is represented in litre (l). 1ml=1cm3. ™™Quantities which cannot be expressed in ™™Least count of screw gauge is 0.01 mm. terms of any other physical quantities are Lease count of Vernier caliper is 0.01 cm. called fundamental quantities. Example: Length, mass, time, temperature etc. ™™Common balance can measure mass accurately upto 5 g. ™™Quantities which can be expressed in terms of fundamental quantities are ™™Accuracy of physical balance is 10 mg. Measurement 10 IX_SCI_EM_Unit-01_PHY.indd 10 12/12/2021 3:57:50 PM  www.tntextbooks.in GLOSSARY Metre [m] Distance light travels, in a vacuum, in 1/299792458th of a second. Mass of an international prototype in the form of a platinum-iridium Kilogram [kg] cylinder kept at Sevres in France. Length of time taken for 9192631770 periods of vibration of the Second [s] Caesium-133 atom to occur. It is that current which produces a specified force between two parallel Ampere [A] wires which are 1 metre apart in a vacuum. Kelvin [K] It is 1/273.16th of the thermodynamic temperature of the triple point of water. Amount of the substance that contains as many elementary units as there Mole [mol] are atoms in 0.012 kg of carbon-12. Intensity of a source of light of a specified frequency, which gives a Candela [cd] specified amount of power in a given direction. TEXTBOOK EXERCISES I. Choose the correct answer. 3. Thickness of a cricket ball is measured by _________ 1. Choose the correct one. a. mm< cm < m < km 4. Radius of a thin wire is measured by ___________ b. mm > cm > m > km c. km < m < cm < mm 5. A physical balance measures small differences in mass up to ______ d. mm > m> cm> km 2. Rulers, measuring tapes and metre scales are used to measure III. State whether true or false. If false, correct the statement. a. mass b. weight c. time d. length 1. The SI unit of electric current is kilogram. 3. 1 metric ton is equal to 2. Kilometre is one of the SI units of measurement. a. 100 quintals b. 10 quintals 3. In everyday life, we use the term weight c. 1/10 quintals d. 1/100 quintals instead of mass. 4. Which among the following is not a device 4. A physical balance is more sensitive than a to measure mass? beam balance. a. Spring balance b. Beam balance 5. One Celsius degree is an interval c. Physical balance d. Digital balance of 1K and zero degree Celsius is 273.15 K. II. Fill in the blanks. 6. With the help of vernier caliper we can have 1. Metre is the unit of ________ an accuracy of 0.1 mm and with screw gauge 2. 1 kg of rice is weighed by ______ we can have an accuracy of 0.01 mm. 11 Measurement IX_SCI_EM_Unit-01_PHY.indd 11 12/12/2021 3:57:50 PM  www.tntextbooks.in IV. Match the following. 4. Define least count of any device. 1. Length kelvin 5. What do you know about pitch of screw Mass metre gauge? Time kilogram 6. Can you find the diameter of a thin wire Temperature second of length 2 m using the ruler from your 2. Screw gauge Vegetables instrument box? Vernier caliper Coins Beam balance Gold ornaments VII. Answer briefly. Digital balance Cricket ball 1. Write the rules that are followed in writing the symbols of units in SI system. V. Assertion and reason type questions. 2. Write the need of a standard unit. Mark the correct answer as: a. Both A and R are true but R is not the 3. Differentiate mass and weight. correct reason. 4. How will you measure the least count of b. Both A and R are true and R is the vernier caliper? correct reason. c. A is true but R is false. VIII. Answer in detail. d. A is false but R is true. 1. Explain a method to find the thickness of a 1. Assertion(A): The scientifically correct hollow tea cup. expression is “ The mass of the bag is 10 kg” Reason (R): In everyday life, we use the term 2. How will you find the thickness of a one weight instead of mass. rupee coin? 2. Assertion (A): 0 °C = 273.16 K. For our convenience we take it as 273 K after IX. Numerical Problems. rounding off the decimal. 1. Inian and Ezhilan argue about the light Reason (R): To convert a temperature on the year. Inian tells that it is 9.46 × 1015 m Celsius scale we have to add 273 to the given and Ezhilan argues that it is 9.46 × 10 12 km. temperature. Who is right? Justify your answer. 3. Assertion (A): Distance between two 2. The main scale reading while measuring celestial bodies is measured in terms of light the thickness of a rubber ball using year. Vernier caliper is 7 cm and the Vernier Reason (R): The distance travelled by the scale coincidence is 6. Find the radius of light in one year is one light year. the ball. VI. Answer very briefly. 3. Find the thickness of a five rupee coin with the screw gauge, if the pitch scale 1. Define measurement. reading is 1 mm and its head scale 2. Define standard unit. coincidence is 68. 3. What is the full form of SI system? 4. Find the mass of an object weighing 98 N. Measurement 12 IX_SCI_EM_Unit-01_PHY.indd 12 12/12/2021 3:57:50 PM  www.tntextbooks.in REFERENCE BOOKS INTERNET RESOURCES 1. Units and Measurements – John Richards. http://www.npl.co.uk/reference/measurement- S. Chand publishing, Ram nagar, New Delhi. units/ http://www.splung.com/content/sid/1/page/units 2. Complete physics (IGCSE) - Oxford http://www.edinformatics.com/math_science/ University press, New York. units.htm 3. Practical physics – Jerry. D. Wilson – https://www.unc.edu/~rowlett/units/dictA.html Saunders college publishing, USA. https://study.com/academy/lesson/standard- units-of-measure.html Concept Map Measurments SI system Physical quantities Measuring instruements Fundamental Derived Fundamental units Venthier Sctewguage quantities quantities Derived units Rules and conventions Spring Common Digital Digital for writing units balance balance balance verner ICT CORNER MEASUREMENT - VERNIER CALIPER Vernier is a visual aid that helps the user to measure the internal and external diameter of the object. This activity helps the students to understand the usage better Step 1. Type the following URL in the browser or scan the QR code from your mobile. Youcan see“Vernier caliper” on the screen. Step 2.The yellow colour scale is movable. Now you can drag and keep the blue colour cylinder in between. Now you can measure the dimension of the cylinder. Use the + symbol to drag cylinder and scale. Step 3. Now go to the place where you can enter your answer. An audio gives you the feedback and you can see the answer on the screen also https://play.google.com/store/apps/details?id=com.ionicframework.vernierapp777926 13 Measurement IX_SCI_EM_Unit-01_PHY.indd 13 12/12/2021 3:57:51 PM