Living Science Physics Class 6 ICSE Solutions Chapter 2 Measurements

ICSE Living Science Physics for Class 6 Solutions Chapter 2 Measurements

Check Your Progress 1 (Page 12)

A. State if the following statements are true or false. Correct the statement if it is false.

Question 1.
In ancient times, a cubit was used to measure the mass of an object.
Answer;
False. In ancient times, a cubit was used to measure the length of an object.

Question 2.
There are seven base units in the SI system.
Answer;
True

Question 3.
Second is considered as the fundamental unit of time in both CGS and MKS systems.
Answer:
True

Question 4.
Centi mean ‘a hundredth part’.
Answer:
True

Question 5.
The symbol used for a unit is always written in capital letters.
Answer:
False. The symbol used for a unit is normally written in smail letters.

B. Answer the following in short.

Question 1.
What do you understand by the term ‘measurement’ ?
Answer:
Determining the exact value of an unknown quantity by comparing it with a known fixed quantity is called as measurement.

Question 2.
What are derived physical quantities ? Give any two examples of derived physical quantities.
Answer:
Physical quantities that are derived from one or more fundamental physical quantities are called derived physical quantities. Examples : area, volume, speed, density, etc.

Question 3.
What are the characteristics of a standard unit ?
Answer:

• It should be accepted universally.
• It should be accurate.
• It should be neither too small nor too big and easy to use.

Question 4.
Mention any two advantages of the metric system over traditional units.
Answer:
1. The metric units are accurate whereas the traditional units were not uniform.
2. The metric system is accepted globally whereas the traditional units had different values at different places.

Question 5.
Which institution in the world maintain the guidelines for using the SI units correctly ?
Answer:
General Conference of Weights and Measures.

C. Answer the following in detail.

Question 1.
What are fundamental physical quantities ? Name any three fundamental physical quantities.
Answer:
Basic physical quantities that do not depend upon other quantities are called fundamental physical quantities. There are seven fundamental quantities – length, mass, temperature, time, electric current, luminous intensity and amount of substance.

Question 2.
Explain by giving two examples why the measurement of a physical quantity is expressed as a combination of a numeral and a unit.
Answer:
To measure a physical quantity, we need to compare it with a known fixed physical quantity of the same kind, i.e., a unit. Hence, the measurement of a physical quantity is always written as a combination of a numeral along with the unit. The numeral specifies the number of times the unit is repeated.

Example :
1. Using a centimetre scale, the length of pencil box is found to be 20 centimetres (cm). 20 cm simply means that the length is 20 times a centimetre. (The centimetre forms the unit of length in a centimetre scale.) Here, the number 20 is the numeral (magnitude) and cm is the unit.
2. Using a weighing (kilogram) scale, the weight of the box is found to be 2 kilograms (kg) 2 kg simply means that the mass of the box is 2 times a kilogram. (The kilogram forms the unit of mass in a kilogram scale). Here, the number 2 is the numeral (magnitude) and kg is the unit.

Question 3.
Explain in detail why there was a need to standardize units.
Answer:
The traditional units were not uniform as the length of a cubit, foot and handspan varied from person to person according to their body size. Similarly, there was no certainty that all grains were exactly the same weight. So these units could not be used.for scientific measurements where accuracy was. a prime concern. The development of a large number of systems of measurement also made it very difficult to conduct trade and commerce between different socities. Therefore, people felt the need to have standard units which could be used for accurate measurement and were accepted universally.

Question 4.
Why are multiples and submultiples of SI units required?
Answer:
Sometimes, the size of the SI unit is either too small or too big to measure a certain quantity. For example, a metre is too small a unit to measure the distance between two cities and too big a unit to measure the thickness of a wire. Hence, multiples and submultiples of units are required. Multiples are factors used to create larger forms whereas submultiples are factors used to create smaller forms of the SI units. For example, a centimetre is a submultiple and kilometre is a multiple of a metre.

Question 5.
State some common rules to write SI units correctly.
Answer:
Guidlines for capitalization

Guidliues for Plurals :

Guidlines for punctuation

Check Your progress (page 20)

A. Tick the most appropriate answer.

Question 1.
The SI unit of mass is –
a. gram
b. milligram
c. kilogram
d. pound
Answer:
c. kilogram

Question 2.
To measure the volume of an irregular shaped body, we use a –
a. graph paper
b. beam balance
c. measuring cylinder
d. ruler
Answer:
c. measuring cylinder

Question 3.
Which of the following weighing devices has a very high accuracy and sensitivity ?
a. Beam balance
b. Grocer’s balance
c. Physical balance
d. Spring balance.
Answer:
c. Physical balance

B. State if the following statements are true or false. Correct the statement if it is false.

Question 1.
Area of an object is a fundamental physical quantity.
Answer:
False. Area of an object is a derived physical quantity.

Question 2.
The error in reading a scale due to the wrong positioning of the eye is called human error.
Answer:
False. The error in reading a scale due to the wrong positioning of the eye is called parallax error.

Question 3.
The region enclosed within the boundaries of a two¬dimensional figure is called its area.
Answer:
True.

Question 4.
The length of an irregular object can be found with the help of a graph paper.
Answer:
False. The area of an irregular object can be found with the help of a graph paper.

C. match the following

1. Length	a. kilogram
2. Mass	b. cubic metre
3. Area	c. metre
4. Volume	d. square metre

Answer:

1. Length	c. metre
2. Mass	a. kilogram
3. Area	d. square metre
4. Volume	b. cubic metre

D. Answer the following in short.

Question 1.
Which unit will you use to find the length of your notebook and why ?
Answer:
Centimetre. Because a notebook has a length for which metre would be too large a unit to measure and millimetre would be too small.

Question 2.
Describe a method by which you can measure the volume of an irregular solid.
Answer:
Aim : To measure the volume of an irregularly shaped stone. Materials Required : Some water, a measuring cylinder, a string and a small stone.

Procedure : Pour some water in the measuring cylinder and read its level from the scale’ marked on the wall of the container. Now tie the string around the stone and lower it into the cylinder without touching its walls until it is completely immersed in water. The level of water in the cylinder rises as the stone is immersed in it. Read the level of water again.

Observation and conclusion : Initial reading of water level = 80 mL (say) Final reading of water level = 130 mL (say) Hence, the volume of the stone = 130 mL – 80 mL = 50 mL.

Question 3.
What do you understand by the term ‘mass’ ? Name any one instrument used for weighing.
Answer:
The amount of matter present in an object is called its mass. Instruments used to measure mass are beam balance, spring balance, physical balance, electronic weighing machines, etc.

Question 4.
Explain the working of a beam balance.
Answer:
A beam balance is the simplest instrument to measure mass (weight). In a beam balance, the mass of an object is measured by comparing it with standard masses called standard weights. A simple beam balance consists of a straight beam of a metal (generally iron), supported at its centre with the help of an iron loop. A pointer is fixed at the centre of the iron loop. Two identical pans are suspended at equal distances from the centre, at the two ends of the beam.

Working : The object whose mass has to be measured is placed on one of the pans (generally the right pan). Standard weights are placed on the other pan until the metallic beam becomes horizontal and the pointer becomes vertical. The sum total of all weights used gives the mass of the object.

E. Find the area of these leaves, where 1 square on the graph paper represents 1 cm².

Question 1.
Ans. The area of leaf 1
= 1 x (Number of complete squares) cm²
+ \(\frac {1}{2}\) x (Number of half or more than half squares) cm²
= 1 x 3 cm² + \(\frac {1}{2}\) x 5 cm²
= 3 cm² + 2.5 cm² = 5.5 cm²

Question 2.
Answer:
The area of leaf 2
= 1 x (Number of complete squares) cm² + \(\frac {1}{2}\) x (Number of half or more than half squares) cm²
= 1 x 3 cm² + \(\frac {1}{2}\) x 5 cm²
= 3 cm² + 2.5 cm² = 5.5 cm²

Question 3.
Answer:
The area of leaf 3
= 1 x (Number of complete squares) cm²
+ \(\frac {1}{2}\) x (Number of half or more than half squares) cm²
= 1 x 7 cm² + \(\frac {1}{2}\) x 9 cm²
= 7 cm² + 4.5 cm² = 11.5 cm²

Question 4.
Answer:
The area of leaf 4
= 1 x (Number of complete squares) cm²
+ \(\frac {1}{2}\) x (Number of half or more than half squares) cm²
= 1 x 6 cm² + \(\frac {1}{2}\) x 8 cm²
= 6 cm² + 4 cm² = 10 cm²

Question 5.
Answer:
The area of leaf 5
– 1 x (Number of complete squares) cm²
+ \(\frac {1}{2}\) x (Number of half or more than half squares) cm²
= 1 x 6 cm² + \(\frac {1}{2}\) x 9 cm²
= 6 cm² + 4.5 cm² = 10.5 cm²

Measurement of Time And Temperature ; Approximations

A. Tick the most appropriate answer.

Question 1.
Which of the following is a fundamental physical quantity?
a. Speed
b. Area
c. Volume
d. Time
Answer:
d. Time

Question 2.
The system of measurement based on centimetre-gram- second is known as
a. SI system
b. FPS system
c. MKS system
d. CGS system
Answer:
d. CGS system

Question 3.
The region enclosed within the boundaries of a closed figure is known as its
a. length
b. area
c. volume
d. temperature
Answer:
b. area

Question 4.
Which of the following devices is used to measure mass?
a. Ruler
b. Measuring cylinder
c. Beam balance
d. temperature
Answer:
c. Beam balance

Question 5.
Which of the following is not a common unit for measuring time ?
a. Hour
b. Mean solar day
c. Year
d. Sundial
Answer:
d. Sundial

Question 6.
A train departs from Delhi railway station at 21:50 hours every day. The time shown in you analogue watch at the departure will be
a. 2:50 a.m
b. 9:50 p.m.
c. 9:50 a.m.
d. 11:50 p.m.
Answer:
b. 9:50 p.m.

Question 7.
The total number of divisions in the Celsius scale is
a: 90
b. 100
c. 180
d. 360
Answer:
b. 100

Question 8.
The maximum and minium thermometer is commonly used by a
a. doctor
b. student
c. meteorologist
d. goldsmith
Answer:
c. meteorologist

B. Fill in the blanks.

Question 1.
There are ………….. fundamental physical quantities.
Answer:
There are seven fundamental physical quantities.

Question 2.
In the ………… system, length is measured in centimetres.
Answer:
In the CGS system, length is measured in centimetres.

Question 3.
1 kilometre is equal to …………. metres.
Answer:
1 kilometre is equal to 1000 metres.

Question 4.
The amount of matter contained in a body is known as its …………
Answer:
the amount of matter contained in a body is known as its mass.

Question 5.
The first two digits in a 24 hour time format represent the number of
Answer:
The first two digits in a 24 hour time format represent the number of hours.

Question 6.
If the departure time of a train on a railway ticket is printed as 20:35, then it will depart at ………. p.m.
Answer:
If the departure time of a train on a railway ticket is printed as 20:35, then it will depart at 8.35 p.m.

Question 7.
The lower fixed point in a laboratory thermometer is the same as that of
Answer:
The lower fixed point in a laboratory thermometer is the same as that of -10°C.

Question 8.
The temperature at which water freezes is known as
Answer;
The temperature at which water freezes is known as ice point.

C. State if the following statements are true or false. Correct the statement if it is false.

Question 1.
The average of a group of observations is calculated by adding all the observations and dividing the sum by the number of observations.
Answer:
True

Question 2.
A laboratory thermometer has a kink in its capillary tube.
Answer:
False. A clinical thermometer has a kink in its capillary tube.

Question 3.
Water is the most commonly used thermometric substance.
Answer:
False. Mercury is the most commonly used thermometric substance.

Question 4.
Mercury docs not stick to the surface of glass.
Answer:
True

Question 5.
1 m = 10,000 cm³
Answer:
False. 1 m = 100 cm

Question 6.
A ruler with a damaged end can be used to measure a length accurately.
Answer:
True

D. Answer the following in a word or two or in a sentence.

Question 1.
Name the unit which is commonly in both the MKS and CGS systems.
Answer:
Second (unit of time)

Question 2.
Name an instrument generally used to find the time interval between two events accurately.
Answer:
Stop watch.

Question 3.
If the alarm of a digital clock is set at 05:50, at what time will the alarm ring during the day ?
Answer:
5.50 a.m.

Question 4.
At what temperature is the upper fixed point of a clinical thermometer kept ?
Answer:
42° C or 108° F

Question 5.
Write the formula for finding the average of a given set of observation. sum of all observations
Answer:

E. Answer the following in short.

Question 1.
What is parallax error ?
Answer:
The error that can arise due to the wrong positioning of the eye while reading a scale is called parallax error.

Question 2.
Explain the working of an extension spring balance.
Answer:
When a body to be weighed is attached to the hook, the coil is stretched downwards. The distance through which the spring gets stretched is measured by a pointer and a graduated scale attached to the spring. The reading on the scale gives the weight of the object.

Question 3.
What do you mean by a mean solar day ?
Answer:
Mean solar day is the time taken by the earth to make one complete rotation about its own axis.

Question 4.
Why is there a slight bend in the capillary tube of a clinical thermometer near the bulb ?
Answer:
A slight bend or kink in the capillary tube of the clinical thermometer near the bulb ensures that the mercury does not move back into the bulb when the thermometer is taken out of a person’s mouth for reading.

Question 5.
What is the function of the bulb in a thermometer ?
Answer:
The bulb in a thermometer is filled with mercuiy. When the bulb is heated, mercury in the bulb expands and rises up in the capillary tube. The height of the mercuiy gives the reading of temperature.

Question 6.
Describe any two means by which the actual capacity of a measuring container can be made less than the correct value by a dishonest trader.
Answer:
(i) The base of the measuring container can be bend inwards by hammering which reduces the capacity of liquid it can hold.
(ii) Some lead can be poured into the measuring container.

F. Answer the following in detail.

Question 1.
What do you understand by the terms volume and capacity ? Which is the most suitable unit for measuring the volume of a/an
a. glass filled with water
b. swimming pool
c. air inside an inflated balloon
d. cylinder of a car engine
Answer:
The total space occupied by an object is called its volume. The maximum volume of a liquid that a container can hold is known as its capacity. Capacity and volume have same units – litres (L) and millilitres (mL).
(a) millilitre (mL)
(b) cubic metre (m³)
(c) millilitre (mL)
(d) cubic centimetre (cc) or cm³)

Question 2.
Explain in detail why railways and airlines use the 24- hour clock format.
Answer:
Railways and airlines use the 24-hour clock format as they operate round the clock (24 hour). The main features of 24- hour clock system are :

• a.m. and p.m. are not used in order to avoid confusion.
• Time is shown by’4 digits. The first two digits indicate the number of hours, and the next two digits indicate the number of minutes.
• Time is expressed continuously from 00.00 (midnight) to 24:00.

Question 3.
Describe the Celsius and Fahrenheit scales.
Answer:
Celsium and Fahrenheit scales are two most common scales used to measure temperature.
The Celsius scale is named after Anders Celsius. The unit of temperature is degree Celsius (°C). The lower fixed point (at which ice melts or water freezes : ice point) is taken as O degree while the upper fixed point (at which water boils :


steam point) is taken as 100 degrees. The distance between these two fixed points is divided into 100 equal parts. Each of these divisions is called 1°C.

The Fahrenheit scale is named after Daniel Gabriel Fahrenheit. The unit of temperature is degree Fahrenheit (°F). The lower fixed point is taken as 32 degrees and the upper fixed point is taken as 212 degrees. The distance between these two points is divided into 180 equal parts. Each of these divisions is called 1°F.

Question 4.
What do you understand by the term temperature ? Distinguish between laboratory’ and clinical thermometers.
Answer:
The degree of hotness or coldness of an object is called its temperature.
Laboratory thermometer :

• It is used to measure temperatures for scientific purposes in a laboratory.
• The kink is not present.
• The lower fixed point is -10°C and upper fixed point is 110°C.

Clinical thermometer:

• It is used to measure temperature of the human body.
• A slight bend or kink is present near the bulb.
• The lower fixed point is 35°C or 95° F and the upper fixed point is 42°C or 108° F.

Question 5.
When are approximations necessary in daily life and when should they be avoided ?
Answer:
An approximation or estimation is a reasonable guess about the measure of a physical quantity. For example, -we use approximation in adding salt to food while cooking. We use approximation when we try to figure out the time it would take to reach a certain place by car. In our daily life, we use approximations in many situations. They are useful as they save time. But, since they are not accurate in measurements, they should be avoided in scientific studies and experimentation.

G. Give reasons for the following.

Question 1.
Body parts should not be used for correct measurements of an object.
Answer:
Body parts have different sizes from person to person and hence the value varies. Since, there is no uniformity or accuracy in the reading, body parts should not be used for correct measurement of an object.

Question 2.
Measurements are very important for life.
Answer:
We need to measure the quantities of most of the things around us to be able to take correct decisions regarding their utility. To find the exactness of an unknown quantity, we need its measurement.

Question 3.
Measuring units are standardized.
Answer:
Measuring units are standardized so that accurate measurement can be done and are accepted universally.

H. Solve the following numerical problems.

Question 1.
Express :
a. 2.25 m in cm
b. 6 L in mL
c. 8000 g in kg
Answer:
a. 2.25 m
= 2.25 x 100 cm [As lm = 100 cm]
= 225 cm

b. 6 l
= 6 x 1000 ml [As 1 l = 1000 ml]
= 6000 ml

c. 8000 g
= 8000 ÷ 1000 kg [As 1000 g = 1 kg]
= 8 kg

Question 2.
20 one-rupee coins are placed one above the other. If their total height is 32 mm, find the thickness of one coin.
Answer:
Number of coins = 20
Total height of coins = 32 mm
Thickness of one coin = ?
Thickness of one coin = img
\(\frac {32}{20}\) = 1.6mm

Question 3.
A piece of wire is wound around a pencil 60 times. If the total width of all the turns is 4 cm, find the diameter of the wire.
Answer:
Number of turns of wire = 60
Total width of turns of wire = 4 cm
Diameter of the wire
\(\frac {4}{60}\) = 0.066cm

Question 4.
Amit dipped a stone tied with a string in a measuring cylinder filled with water. If the initial level of water was 56 mL and after dipping the stone the final level of water was 78 mL, find the volume of the stone.
Answer:
Initial level of water = 56 mL Final level of water = 78mL Volume of the stone = ?
Volume of the stone = Final reading – Initial reading = 78mL – 56 mL = 22 mL

Question 5.
Grass is to be laid a rectangular field of dimensions 55 m x 45 m. Calculate the area of the field.
Answer:
Length of field = 55 m Breadth of field = 45 m
Area of rectangular field = length x breadth = 55 x 45 m2 = 2,475 m2

Question 6.
A lawn is in the shape of a square. Find the area covered by the iawn if each of its sides is 50 m.
Answer:
Length of each side = 50 m
Area of square lawn = side x side = 50 x 50 nr = 2500 m2

Question 7.
An aeroplane leaves Bengaluru at 23:50 hours and reaches Chennai at 00.40 hours. Rewrite the statement using a 12-hour time format. Also find the duration of the flight.
Answer:
Aeroplane leaves Bengaluru at 11:50 p.m.
and reaches Chennai at 12:40 a.m.
Duration of the flight = 50 minutes

Question 8.
The body temperature of a patient on Monday was 102 °F and on Tuesday it was 104°F. What was the rise in temperature during these two days ?
Answer:
Body temperature on Monday = 102°F
Body temperature on Tuesday = 104°F
Rise in temperature = 104 – 102°F = 2°F

Question 9.
The masses of five marbles are 50 g, 55 g, 60 g, 65 g and 70 g. Find their average mass.
Answer:
The sum of masses of all marbles
= 50 g + 55 g + 60 g + 65 g + 70 g = 300 g
Number of marbles = 5
Average mass of a marble  
\(\frac {300}{5}\)
= 60 g

Question 10.
The rainfall in a city on each day of a week is recorded below. Find the average rainfall for the week.

Answer:
The sum of recorded rainfall
1.2 mm + 10.3 mm + 5.5 mm + 13.5 mm + 7 mm + 1mm = 38.5 mm Number of days = 7
Average rainfall of the week
= \(\frac {38.5}{7}\)mm = 5.5 mm

I. Write down the time in a 24-hour format
Clock

Answer:
13:20

Answer:
04:45

Answer:
13:20

Answer:
9:35

 

Living Science Physics Class 6 ICSE Solutions