Chapter: 02. Physical Quantities And Measurement 1
CONNECT
Flour: Digital scale / Beam balance Length of cloth: Metre scale / Measuring tape Sugar: Digital scale / Beam balance Length of table: Measuring tape / Metre scale Vegetables: Digital scale / Beam balance CHECK YOUR PROGRESS (Observe the ruler)
How many centimetres are there? Typically, a standard geometry box ruler has 15 cm. (This can vary, common sizes are 15 cm or 30 cm). How many millimetres are equal to 1 centimetre? 10 millimetres are equal to 1 centimetre. How many inches are there? Typically, a standard geometry box ruler has 6 inches or 12 inches (depending on length). Approximately how many millimetres are equal to 1 inch? Approximately 25.4 millimetres are equal to 1 inch. REASON CORNER
We don’t use a measuring tape to measure the distance from Delhi to Chennai because the distance between two cities is enormous (hundreds or thousands of kilometres). A measuring tape, even a long one, is impractical and highly inefficient for such vast distances. Kilometres are the appropriate and practical unit for measuring inter-city distances. CHECK YOUR PROGRESS (Choose the correct option - Mass units)
The standard unit of mass in SI system is PREPPING FOR PISA
Based on your understanding of the passage, complete the table given below.
2. Based on the graph given above, between which two successive years was the adulteration of food highest? What was the change in percentage of adulteration in comparison to that of the previous year? The highest increase in adulteration was between 2017-18 (18.4%) and 2018-19 (25.2%). The change in percentage was 25.2% - 18.4% = 6.8%. Assertion (A): Food adulteration is done to increase profits.
Reason ®: Adulterated food can make people sick and force them to spend more money in medical treatment. b. Both A and R are true but R is not the correct explanation of A. LIFE SKILLS
My ribbon is 1 m (metre) or 1 cm (centimetre) long. I cycle 5 km (kilometres) to school. My pencil is 20 cm (centimetres) long. I weigh 30 kg (kilograms). My mother needs 500 kg of sugar for the cake. My mother needs 500 g (grams) of sugar for the cake. EVALUATION
A. Choose the correct option.
The diameter of a tree can be easily measured by using a The standard unit of area in SI system is The mass of a human being is generally expressed in A quantity that can be measured is known as Which instrument will be used to measure the mass of a medicine tablet? A length of 300 cm is expressed in metres as While measuring length using a metre scale, the position of the eye b. should be vertically above the point from where the measurement is to be taken. Which of the following precautions must be taken while taking measurement of length? b. The measurement should be taken from the mark clearly visible on the scale. B. Fill in the blanks.
Measurement involves two parts, a numerical value and a unit. 1000 m make one kilometre. 1 square metre is the area of a square with side 1 metre. Kilometre is a multiple while centimetre and millimetre are the submultiples of the standard unit metre. Area of regular shapes can be determined using a graph paper. C. Name the following:
the error that occurs due to incorrect positioning of the eye the units for measurement used by scientists all over the world SI units (or International System of Units) the amount of space covered by a flat surface quantity of matter contained in a body D. Write true (T) or false (F) against the following statements.
One metre is equal to 1000 centimetres. A metre scale can be used to determine the mass of a body. The mass of a soap cake would be measured in square cm. The hole on the standard weights is filled by lead. When weighing something on an electronic balance, it needs to be tared first. The full form of NPL is National Physical Laboratory. Before buying anything from the market, we should always check the colour of the standard weights. E. Give a suitable unit used to measure the following:
distance between two towns gram (g) or milligram (mg) area of the school playground F. Short answer type questions.
Measurement is the comparison of an unknown quantity with a known fixed quantity of the same kind. Define length. Name three instruments used to measure it. Length is the distance between any two points or places. Three instruments used to measure it are the ruler, metre scale, and measuring tape. Name the multiples and submultiples of metre and their relation with metre. Multiple of metre: Kilometre (km); 1 km = 1000 m. Submultiples of metre: Centimetre (cm); 1 m = 100 cm, and Millimetre (mm); 1 cm = 10 mm. What is parallax error? How can it be avoided? Parallax error is the error that occurs due to incorrect positioning of the eye while taking a measurement. It can be avoided by keeping the eye vertically above the point from where the measurement is to be taken, and ideally, by keeping one eye shut. What do you understand by area? Give its standard unit in SI system. Area is the amount of space occupied by a flat surface. Its standard unit in the SI system is the square metre (m²). Define mass. Name the instruments used to measure mass. Mass is the quantity of matter contained in a body. The instruments used to measure mass are the beam balance (or physical balance) and the electronic balance. G. Long answer type questions.
What precautions need to be taken while measuring the length of a wooden block using a metre scale? Precautions include: placing the object on a flat surface; placing the metre scale exactly along the length of the object with its zero mark coinciding with one end; keeping the eye vertically above the point of measurement to avoid parallax error; and if the zero mark is worn out, starting measurement from another clear mark and subtracting that initial reading from the final reading. Write a short note on beam balance. A beam balance is an instrument used to measure mass. It consists of a horizontal beam supported at its centre, with a pointer fixed at the centre. Two identical pans hang from either side of the beam. The object to be weighed is placed in one pan, and known standard weights are placed in the other pan until the beam becomes horizontal and the pointer aligns vertically, indicating equal mass in both pans. The total of the standard weights then gives the mass of the object. Explain how the department of weights and measures, Government of India, helps in maintaining the standard of weights in the country. The Department of Weights and Measures ensures fair trade and consumer protection by maintaining measurement standards. They do this by calibrating and certifying standard weights (which have a lead-filled hole stamped with their seal of approval), conducting regular inspections to ensure proper use of calibrated instruments, enforcing legal metrology rules to prevent fraud (like removing lead from weights), and ensuring adherence to national measurement standards maintained by institutions like the National Physical Laboratory (NPL). Higher Order Thinking Skills (HOTS)
Assertion (A): Kilogram is the standard unit of mass.
Reason ®: Kilogram is well-defined and invariant. a. Both A and R are true and R is the correct explanation of A. You are given a thread and a metre scale. How will you estimate the length of the curved line? To estimate the length of a curved line: carefully place the thread exactly along the entire length of the curved line, following all its bends and curves. Mark the starting and ending points of the curved line on the thread. Then, straighten the thread and measure the distance between the two marks using the metre scale. This measurement will be the approximate length of the curved line. Integrate
Why are the S.I. units of area and mass not used to represent the data in the table? SI units are not used because the quantities involved (e.g., area in “Lakh hectare” and production in “Million Tonnes”) are very large at a national scale. Using these larger, conventional units makes the data more manageable, readable, and comprehensible for agricultural and economic analysis, avoiding excessively long numerical values if expressed in base SI units. According to the data given above, which crop has the lowest yield? Plot the yield of this crop for the years 2017-18, 2018-19 and 2019-20 on a graph paper. According to the data, Pulses have the lowest yield. Yield of Pulses: 2017-18 (853 kg/hectare), 2018-19 (757 kg/hectare), 2019-20 (817 kg/hectare). (To plot, you would mark these three points on a graph with “Year” on the x-axis and “Yield (kg/hectare)” on the y-axis.) Find out why rice and wheat are grown on such a large scale in India. Rice and wheat are grown on a large scale in India because they are the staple food crops for the majority of the Indian population, providing essential carbohydrates and energy. Their widespread cultivation is crucial for ensuring national food security and meeting the dietary needs of the country’s vast population. 
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