**Selina Concise Class 6 Physics Solution Chapter No. 2- ‘Physical Quantities and Measurement’ For ICSE Board Students.**

**(A) Objective Questions Solution:**

**(1) Write true or false for each statement:**

(a) S.I. unit of temperature is Fahrenheit.

Ans. False

(b) Every measurement involves two things – a number and a unit.

Ans. True.

(c) Mass is the measure of quantity of matter.

Ans. True

(d) The S.I. unit of time is hour.

Ans. False

(e) Area can be expressed as the product of lengths of two sides.

Ans. True

**(2) Fill in the blanks**

(a) The S.I. unit of length is ______ of time is _____, of mass is _____

Ans. metre, second, kilogram.

(b) ^{o}C is the unit of _______

Ans. temperature.

(c) 1 metric tonne = _____ kg

Ans. 1000

(d) The zero mark in celsius thermometer is the melting point of _____

Ans. ice

(e) The thermometer used to measure the human body temperature is called the ______ thermometer.

Ans. clinical

(f) The normal temperature of human body is _______ ^{o}C or _______ ^{o}F.

Ans. 37,98.6

(g) The ______ of an object is measured with the help of a beam balance.

Ans. mass.

**(3) Match the following columns:**

Column A |
Column B |

(a) Length of a housing plot | (i) clock |

(b) Breadth of a book | (ii) Beam balance |

(c) Mass of an apple | (iii) Thermometer |

(d) Period of Time for study | (iv) Measuring tape |

(e) temperature of a body | (v) Graph paper |

(f) Surface area of a leaf | (vi) Metre ruler |

**Answer:**

Column A |
Column B |

(a) Length of a housing plot | (iv) Measuring tape |

(b) Breadth of a book | (vi) Metre ruler |

(c) Mass of an apple | (ii) Beam balance |

(d) Period of Time for study | (i) clock |

(e) temperature of a body | (iii) Thermometer |

(f) Surface area of a leaf | (v) Graph paper |

**(4) Select the correct alternative:**

**(a) The symbol of degree celsius is:**

(i) ^{o}C

(ii) ^{o}F

(c) K

(d) ^{o}K

Ans. ^{o}C

**(b) 10 mm is equal to:**

(i) 1 cm

(ii) 1 m

(iii) 10 dm

(iv) 10 cm

Ans. (i) 1 cm

**(c) The amount of surface occupied by an object is called its:**

(i) volume

(ii) area

(iii) mass

(iv) length

Ans. (ii) area

**(d) A metre ruler is graduated in:**

(i) m

(ii) cm

(iii) mm

(d) km

Ans. mm

**(e) A thermometer is graduated in:**

(i) Kelvin

(ii) ^{o}C

(iii) g

(iv) cm

Ans. ^{o}C

**(B) Short / Long Answer Questions Solution:**

**(1) What is measurement? How is measurement expressed?**

Ans. Measurement is a comparison of an unknown quantity with a known fixed quantity of the same kind.

Measurement is expressed by units (u).

**(2) State two characteristics of a unit.**

Ans. Two characteristics of a unit are:

(i) It should be of convenient size.

(ii) It must be universally accepted i.e. its value must remain same at all places and at all times. Irt shoud not change with the change of place of time.

(3) Name four basic measurements in our daily life.

Ans. Four basic movement in our daily life are :

(i) Measurement of length, (ii) Measurement of mass, (iii) Measurement of time, (iv) Measurement of temperature.

**(4) What are the S.I. units of (i) mass (ii) length (iii) time and (iv) temperature? Write their names and symbols.**

Ans.(i) The SI unit of mass is kilogram and it is symbolized by kg.

(ii) The SI unit of length is metre and it is symbolized by m.

(iii) The SI unit of time is second and it is symbolized by S.

(iv) The SI unit of temperature is Kelvin and it is symbolized by K.

**(5) Define one metre, the SI unit of length. State its one multiple and one sub multiple.**

Ans. One metre is defined as the distance travelled by light in air in 1/299,792,458 of a second.

Simple multiples and sub multiples of metre: It is not convenient to express long lengths in terms of metre. They are expressed in kilometer (in short of km).

**Multiple: **1 km = 1000 m

**Submultiples: **1 cm = 1/100 m or 10^{-2} cm

**(6) Convert the following quantities as indicated:**

(a) 12 inch = 1 feet

(b) 1 ft = 30.48 cm.

(c) 20 cm = 0.2 m

(d) 4.2 m = 420 cm

(e) 0.2 km = 200 m

(f) 0.2 cm = 2 mm

(g) 1 yard = 0.91 m.

**(7) (a) Describe in steps how would you measure the length of a pencil using a meter scale. Draw a diagram if necessary.**

**(b) Explain with an example how you will use the metre ruler in part (a) if the ends of ruler are broken.**

Ans. (a) To measure the length of a pencil with a meter scale, the scale is placed with its marking close to the object.

Then the zero mark on the scale is made to coincide with one end of the object. Now the position of the other end of the object is read on the scale.

This reading gives the length of the pencil.

(b) Sometimes the ends of the ruler get damaged with use and its zero mark may not be visible. To measure the length of an object (like example rod) )with such a ruler, the object is placed close to specific marking on the ruler and positions of both ends of the object are read on the ruler. The difference of the two readings gives the length of the object.

**(8) Name the device which you will use to measure the perimeter of your play ground. Describe in steps how you will use it.**

Ans. The measuring tape is used to measure the perimeter of the ground.

**Step by Step to measure the perimeter of playground are follows: **

Step 1: Take a measuring tape.

Step 2: Rolled it to open and placed in one of the corner of playground.

Step 3: Extend the tape upto the end position.

Step 4: Write the measurement on sheet.

Step 5: Take the measure of length and breadth of the playground in above ways.

Step 6: As took the both measurement, place the number in the laws of perimeter to find it.

**(9) The diagram below shows a stick placed along a meter ruler. The length of the stick is measured keeping the eye at positions A, B and C.**

**(a) Write the length of stick PQ as observed, for each position of the eye. Are they all same?**

**(b) Which is the correct position of the eye? Write the correct length of the stick.**

**(a) Ans. **From position A the length of PQ is 3.5 cm

From position B the length is 3.2 cm

From position C the length is 3 cm.

(b) Here B is the correct position of the eye.

The correct length of the stick is is 3.2 cm.

**(10) Define mass. State its (i) S.I. (ii) C.G.S and (iii) F.P.S units. How are they related?**

**Ans. (i) **The mass of a body is its quantity of matter contained in it.

**The unit in Mass are:-**

C.G.S. |
F.P.S. |
S.I. |

Gram (g) | Pound (lb) | Kilogram (kg) |

**Relationship between gram, kilogram and pound:**

1 g = 1/1000 kg = 10^{-3} kg

1 lb = 453.59 g.

**(11) Convert the following quantities as indicated:**

(a) 2500 kg = 2.5 metric tonne.

(b) 150 kg = 1.5 quintal.

(c) 10 lb = 4.5359 kg

(d) 2500 g = 2.5 kg

(e) 0.01 kg = 10 g

(f) 5 mg = 5 x 10^{-6} kg.

**(12) Name the instrument which is commonly used to measure the mass of a body. State how it is used.**

Ans. The instrument which are commonly used to measure the mass of the body:

(a) The beam balance

(b) The electronic balance.

**Use of a beam balance to measure the mass of a body:**

To measure the mass of an object , standard weights are used (20 kg, 10 kg, 5 kg, 2 kg, and 1 kg) However smaller weights of 500 g, 200 g, 100 g, 50 g, 20 g, 10 g and 5 g are also available.

For measuring, the beam balance is first held up. On holding up the balance, it is ensured that when there is nothing on either pan, the beam is horizontal. The body whose mass is to be measured is placed on the left pan. The standard weights are placed on the right pan. They are so adjusted that the beam is again horizontal on holding the balance up.

The total of the standard gives the mass of the given body.

** (13) Define one kilogram, the S.I. unit of mass. How is it related to (i) quintal (ii) metric tonne and (iii) gram?**

Ans. One kilogram was defined as the mass of a cylinder of platinum-iridium allow kept at the international bureau of weights and measures at Sevres near Paris.

**Relation of Kilogram (kg) to quintal, metric tonne and gram:**

One hundred kilogram make one quintal i.e. 1 quintal = 100 kg.

Ten quintal make one metric tonne i.e.

1 metric tonne = 10 quintal = 1000 kg

One gram is the one thousandth part of a kilogram or one thousand gram make one kilogram i.e. 1 kg = 1000 g or 1 g = 1/1000 kg.

**(14) Name and define the SI unit of time. How is it related to (i) minute (ii) hour (iii) day and (iv) year?**

**Ans. **The S.I. unit of time is second. In short form, it is written by the letter s.

(i) 1 minute = 60 seconds.

(ii) 1 hour = 60 minute = 60 x 60 = 3600 seconds.

(iii) 1 day = 24 hours = 24 x 60 min = 1440 min = 1440 x 60 s = 86400 s

(iv) 1 year = 365 days = 365 x 86400 s = 3.15 x 10^{7} s.

**(15) Name two devices used to measure the short time interval of an event.**

Ans. Two devices used to measure the short time interval of an event are – (i) Pendulum clock (ii) A watch.

**(16) Express in second (i) 3 minute 15 seconds and (ii) 5 hour 2 minute 5 second.**

**Ans. (i) 3 minute 15 seconds**

= 3 x 60 + 15

= 180 + 15

= 195 seconds.

**(ii) 5 hour 2 minute 5 second.**

= 5 x 3600 + 2 x 60 + 5

= 18000 + 120 + 5

= 18125 seconds.

**(17) What does the temperature measure?**

**Ans. **Temperature is the measure of degree of hotness or coldness of an object.

**(18) Name the (i) S.I. unit and (ii) one common unit of temperature. Write their symbols also.**

**Ans. **(i) The SI unit of temperature is Kelvin. The symbol of Kelvin is k.

(ii) One common unit of temperature is degree celsius (^{o}C)

**(19) Name the instrument used for measuring temperature of a person. Draw a leveled diagram.**

**Ans. **Clinical Thermometer.

**(20) Write the temperature of (i) melting ice (ii) boiling.**

**Ans. **(i) Temperature of melting ice is 0 degree celsius.

(ii) Temperature of boiling is 100 degree celsius.

**(21) What is clinical thermometer? State its special features. Draw a labeled neat diagram of a clinical thermometer showing the range of temperature marked on it.**

Ans. A clinical thermometer has the marking from 35^{o} C to 42^{o} C. It has a slight bend or kink in the stem just above the bulb. This kink prevent the mercury from falling back all by itself.

Special features of Clinical thermometer:

It measures the temperature of a patient’s body with a clinical thermometer.

**(22) What is the normal temperature of the human body? How is it indicated in a clinical thermometer?**

Ans. The normal temperature of the human body is 37^{o} C or 98.6^{o} F.

This temperature is marked by a red arrow.

**(23) Can a clinical thermometer be used to measure the temperature of boiling water? Give reasons for your answer.**

Ans. No, a clinical thermometer can’t be used to measure the temperature of boiling water.

A clinical thermometer can not be used to measure the temperature of boiling water i.e. 100 degree celsius because it can measure only up to 42 degree celsius.

**(24) Explain the term ‘area of a surface’.**

**Ans. **The total surface occupied by an object is called its surface area.

**(25) Name the SI unit of area and define it.**

**Ans. **The SI unit of area is square metre (m^{2}).

One square metre is the area of a square of each side of 1 metre.

**(26) How are the units (i) square yard (ii) hectare (iii) km ^{2} (iv) cm^{2} (v) mm^{2} related to the SI unit of are**

Ans. (i) 1 square yard = 1 yard x 1 yard

= 0.9144 m x 0.9144 m

= 0.836 m^{2} (or 0.84 m^{2} nearly).

(ii) 1 hectare = 10000 m^{2} = 100 are

(iii) 1 km^{2} = 1000,000 m^{2}

= 100 hectare

(iv) 1 cm^{2} = (1/10000) m^{2} or 10^{-4} m^{2}

(v) 1 mm^{2} = 10^{-6} m^{2}

**(27) Explain how you will the measure the area of (i) a square (b) a leaf?**

Ans. (i) To find the area of square we have to measures its one length. If the length of the one side is 7 cm, then area of the square = 7^{2} = 49 cm^{2}.

(b)