Samacheer Kalvi Class 6 Science Solutions Term 1 Chapter 1 Measurements

Property	Definition	Basic Unit	Instrument used for measuring
Length	The distance between one end and the other desired end.	Metre (m)	Metre scale, measuring tape.
Mass	Mass is the measure of the amount of matter in an object.	Kilogram (kg)	Beam balance, Electronic balance.
Volume	The amount of space that an object occupies (or) that is enclosed within a container.	Cubic metre (m³), Litres	Graduated cylinder, beaker, pipettes, and burette.
Time	Interval between two events.	seconds	Sand clock, electronic clock, stop watches.

Answer: The completed chart is shown above.
In simple words: This chart explains what each property means, its standard unit, and the tools we use to measure it. For example, length is distance, measured in metres with a scale. Mass is the amount of stuff, in kilograms, using a balance. Volume is space taken up, in cubic metres or litres, measured by cylinders. Time is how long between events, in seconds, measured by clocks.

🎯 Exam Tip: For each fundamental physical quantity, be ready to state its definition, its SI unit, and at least two common measuring instruments.

 

I. Choose The Best Option:

 

Question 1. What is 7 m in mm?
(a) 0.7 mm
(b) 700 mm
(c) 7000 mm
(d) 70 mm
Answer: (c) 7000 mm
In simple words: To change metres to millimetres, you multiply by 1000. So, 7 metres becomes 7000 millimetres. This is because 1 metre has 1000 millimetres.

🎯 Exam Tip: Remember that \( 1 \text{ m} = 100 \text{ cm} \) and \( 1 \text{ cm} = 10 \text{ mm} \). So, \( 1 \text{ m} = 100 \times 10 \text{ mm} = 1000 \text{ mm} \).

 

Question 2. The distance between one end and the other end is called ..........
(a) mass
(b) length
(c) time
(d) None of the options
Answer: (b) length
In simple words: The distance from one point to another is what we call length.

🎯 Exam Tip: Understand the basic definitions of physical quantities. Length is a direct measure of spatial extent.

 

Question 3. What is the unit of length?
(a) metre
(b) litre
(c) second
(d) kilogram.
Answer: (a) metre
In simple words: The standard unit for measuring length is the metre. Litre is for volume, second for time, and kilogram for mass.

🎯 Exam Tip: Be able to identify the correct SI unit for each fundamental quantity. Metre is specifically for length.

 

Question 4. Five kilometre is equal to __________
(a) 500 cm
(b) 500 m
(c) 5000 m
(d) 5000 cm
Answer: (c) 5000 m
In simple words: Since one kilometre is 1000 metres, five kilometres would be five times 1000 metres, which is 5000 metres.

🎯 Exam Tip: Quickly recall the 'kilo' prefix, which means 1000. So, kilometres are 1000 times larger than metres.

 

Question 5. These are the instruments used in measuring the volume of objects with irregular shapes.
(a) Balance
(b) Electronic balance
(c) Displacement of water method
(d) sand clock.
Answer: (c) Displacement of water method.
In simple words: For things with strange shapes, you can find their volume by seeing how much water they push out when put into it. This is called the water displacement method.

🎯 Exam Tip: The water displacement method (Archimedes' principle) is a classic technique for finding the volume of irregularly shaped objects.

 

II. True Or False:

 

Question 1. The comparison of a known quantity with the unknown quantity is the mass.
Question 2. The area can be calculated by using the two lengths and width.
Question 3. Using electronic balance weight can be measured accurately.
Answer:
1. False
2. True
3. False.
In simple words: Comparing known and unknown is called measurement, not mass. Area is found by multiplying length and width. An electronic balance measures mass, not weight directly.

🎯 Exam Tip: Be careful with definitions: 'measurement' is the comparison, 'mass' is a quantity. Also, be precise about what instruments measure (e.g., electronic balances measure mass).

 

III. Fill In The Blanks.

 

Question 1. \( 78.75 \text{ cm} = \) .......... m .......... cm
Question 2. \( 1195 \text{ m} = \) .......... km .......... m
Question 3. \( 15 \text{ cm} \ 10 \text{ mm} = \) .......... mm
Question 4. \( 45 \text{ km} \ 33 \text{ m} = \) .......... m.
Question 5. The metric system of unit is developed in the year .......... by French.
Answer:
1. 0 m, 78.75 cm (or 0.7875 m, 0 cm)
2. 1 km, 195 m
3. 160 mm
4. 45033 m
5. 1790
In simple words: \( 78.75 \text{ cm} \) is less than 1 metre, so it's 0 metres and 78.75 centimetres. \( 1195 \text{ m} \) is 1 kilometre and 195 metres. \( 15 \text{ cm} \) is \( 150 \text{ mm} \), so with \( 10 \text{ mm} \) it becomes \( 160 \text{ mm} \). \( 45 \text{ km} \) is \( 45000 \text{ m} \), plus \( 33 \text{ m} \) makes \( 45033 \text{ m} \). The metric system was started by the French in 1790.

🎯 Exam Tip: For conversions, always remember that 1 m = 100 cm, 1 km = 1000 m, and 1 cm = 10 mm. The year 1790 is key for the origin of the metric system.

IV. Matching

 

Question 1. Match the following.

Answer:
1. - d (Length - metre)
2. - c (Mass - Kilogram)
3. - b (Time - Seconds)
4. - a (Volume of liquid - Litre)
In simple words: We connect each physical property or type of quantity from Column A to its correct unit or related term in Column B. This shows how different things are measured.

🎯 Exam Tip: For matching questions, it is helpful to first identify the most obvious pairs, then eliminate options to find the correct matches for the remaining items. Ensure all items are correctly paired.

 

Question 2. Match the following.

Answer:
1. - d (1000 gm - 1 kilogram)
2. - c (1000 milligram - 1 gram)
3. - b (1000 kilogram - 1 ton)
4. - a (1000 metre - 1 kilo meter)
In simple words: This question asks us to link amounts of mass and distance to their equal values in different units. It helps us remember common conversions, like how many grams make a kilogram.

🎯 Exam Tip: Understanding conversion factors (like 1000 grams = 1 kilogram) is key for these questions. Practice common metric conversions to answer quickly and accurately.

V. Write the Following Unit in Ascending Order.

 

Question 1. Arrange the following units in ascending order: Ton - gram - kilogram - Metric ton.
Answer: Gram - kilogram - ton - metric ton.
In simple words: When we put these units of mass in order from smallest to largest, gram comes first, then kilogram, followed by ton, and finally metric ton, which is the biggest.

🎯 Exam Tip: Remember that "ton" is often used interchangeably with "short ton" (around 907 kg) or "long ton" (around 1016 kg) in some contexts, but a "metric ton" is precisely 1000 kg. For typical school problems, assume "ton" refers to the common non-metric ton, which is smaller than a metric ton.

VI. Very Short Answer (2 Marks)

 

Question 1. What is length?
Answer: Length is the distance measured from one point to another desired point. It tells us how far apart two ends are.
In simple words: Length is simply how long something is, or the distance from its start to its end.

🎯 Exam Tip: When defining basic terms, keep your answer clear and concise, focusing on the core concept. Mentioning "distance between two points" is key for length.

 

Question 2. Differentiate mass from weight.
Answer:
Mass: This is the amount of matter an object has. Its unit is the kilogram (kg). Mass remains the same no matter where the object is, even in space.
Weight: This is the force of gravity pulling on an object's mass. Its unit is the Newton (N). Weight changes depending on the gravitational pull, so an object weighs less on the moon than on Earth.
In simple words: Mass is how much "stuff" is in an object, always the same. Weight is how hard gravity pulls on that "stuff", which changes depending on the planet or moon.

🎯 Exam Tip: When differentiating, define both terms clearly and highlight the key differences. For mass and weight, remember mass is constant, but weight depends on gravity. Always mention their respective SI units.

 

Question 3. List the SI units of length, mass, and time.
Answer:
1. The SI unit for length is metre (m).
2. The SI unit for mass is kilogram (kg).
3. The SI unit for time is second (s). These are fundamental units in physics.
In simple words: For length, we use metres. For mass, we use kilograms. For time, we use seconds. These are the main units for these basic things.

🎯 Exam Tip: The SI units are universally accepted. Memorizing the correct SI units for fundamental quantities like length, mass, and time is crucial for physics and science exams.

 

Question 4. What are the basic quantities of physics?
Answer: The three basic quantities of physics are:
1. Length
2. Mass
3. Time
These are also known as fundamental quantities.
In simple words: The main things we measure in science are length, mass, and time. These are the building blocks for understanding everything else.

🎯 Exam Tip: Understand why these three are considered "basic" or "fundamental" – they cannot be defined in terms of other physical quantities and form the basis for all other measurements.

 

Question 5. Differentiate between Mass and Weight.
Answer:
Mass:
• Mass describes the total amount of material present in an object. It is a fundamental property of matter.
• A beam balance is commonly used to measure mass.
Weight:
• Weight is the force exerted on an object due to gravity. This force changes with the strength of gravity.
• An electronic balance is typically used to measure weight accurately.
In simple words: Mass is how much "stuff" something has, and we use a regular balance to find it. Weight is how hard gravity pulls on that "stuff," and we use an electronic scale for that.

🎯 Exam Tip: When differentiating, ensure you highlight both what each quantity represents and how it is measured. Mass is constant everywhere, while weight varies with gravity.

 

Question 6. What clocks are used to measure time accurately?
Answer: The clocks used to measure time accurately are:
1. Electronic clock
2. Stopwatch (often called a stop clock)
These devices are designed to precisely track short or long durations. They are used in various fields where precise timing is essential.
In simple words: To get time exactly right, we use electronic clocks or stopwatches. They help us count time very carefully.

🎯 Exam Tip: For accuracy in time measurement, electronic devices are preferred over traditional mechanical clocks due to their digital precision and ability to record fractions of a second.

 

Question 7. Hold a sheet of paper in one hand and a book in the other. Which hand feels heavier, and why?
Answer: The hand holding the book will feel heavier. This is because the book has much more mass than a single sheet of paper. Due to its greater mass, the Earth's gravity pulls on the book with more force. This means your hand needs to apply more upward force to hold the book steady, making it feel heavier.
In simple words: The book feels heavier because it has more "stuff" in it (more mass). Gravity pulls harder on more mass, so your hand has to work harder to hold the book up.

🎯 Exam Tip: Relate observed phenomena to fundamental concepts like mass and gravity. The key is to explain that greater mass leads to a greater gravitational force (weight), which your hand perceives as heavier.

VII. Give Detailed Answers: (5 Marks)

 

Question 1. What important features should we consider for accurate measurement?
Answer: To get an accurate measurement, we should pay attention to these features:
1. **Starting Point:** Always begin measuring from the zero ('0') mark on the scale.
2. **Alignment:** Ensure the object being measured is placed exactly parallel to the scale.
3. **Correct Reading:** Your eye must be positioned vertically right above the point being measured to avoid parallax error. First, note the bigger divisions (like cm), then the smaller divisions (like mm), and combine them. For example, if a pencil length is 6 cm and 2 mm, write it as 6.2 cm.
4. **Stability:** Keep both the scale and the object still while taking the measurement.
In simple words: To measure well, always start from zero, keep the object straight, look directly down at the reading, and first count big marks then small marks on the scale.

🎯 Exam Tip: Focus on the common sources of error in measurement (like parallax and incorrect starting points) and how to avoid them. Listing them clearly and concisely helps score full marks.

 

Question 2. How will you measure the volume of an irregularly shaped object?
Answer: We can find the volume of an irregularly shaped object using the water displacement method:
1. First, pour a measured amount of water (for example, 50 ml) into a graduated measuring cylinder.
2. Carefully tie the irregular object, such as a stone, with a fine thread.
3. Gently lower the object into the water until it is fully submerged.
4. Observe the water level rise in the cylinder. For instance, if the water level rises to 75 ml, the difference (75 ml - 50 ml = 25 ml) is the volume of the object. This rise happens because the object pushes aside its own volume of water.
In simple words: To find the space an odd-shaped object takes up, put some water in a marked cup and note the level. Then, put the object fully in the water. The new, higher water level minus the first level tells you the object's volume.

🎯 Exam Tip: This method (Archimedes' principle) accurately measures the volume of irregular solids. Ensure the object is fully submerged and no air bubbles are trapped, as this can affect the accuracy of the reading.