Short/long answer questions-(Q1 -Q12) of chapter-2(physical quantities & measurement) of class-6

 1. What is measurement ? how is a measurement expressed?

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

Measurement=n×u ,

   n=number (magnitude)

   u=unit

2. State two characteristics of a unit.

Ans.  Two characteristics of unit are:

1. It should be of convenient size.

2 it must be universally accepted ..its value must remain same at all places and at all times it should not change with the change of place or time.

3. Name four basic measurements in our daily life.

Ans. 4 basic measurements in our daily life are as follows:

1. Length

2. Mass

3. Time

4. Temperature

4. What are the SI units of mass, length, time and temperature ?write their names and symbols.

Ans. 1.mass- kilogram- kg

2. Length- metre- m

3. Time- second- s

4. Temperature- Kelvin- K

5. Define 1 metre ,the SI unit of length .state its one multiple and one sub multiple.

Ans. A metre was initially defined as the distance between two points on a rod of Platinum-irridium alloy kept at zero degree celsius in the International Bureau of weights and measures at sevres near Paris.

One multiple is km

1km=1000m

One sub multiple is centimetre.

1cm=1/100 m

6. Convert the the following quantities as indicated:

a) 12 inch= ....1..ft

b) 1 ft =..30.48...cm

c)20 cm=..0.2...m, 1m=100cm , 1/100 m= 1cm, 20×1/100 m = 20×1cm ,           1/5 m= 20 cm ,                   0.2 m=20 cm.

d) 4.2 m = ..420.. cm,1m =100 cm ,4.2×1m= 4.2×100cm

4.2 m=420cm.

e) 0.2 km=...200.. m, 1km= 1000m,

0.2×1 km=0.2 ×1000m ,

0.2 km= 200m

f)0.2 cm =  ....2 mm, 1cm= 10mm,

0.2 × 1 cm=0.2×10 mm ,0.2 cm=2mm

g) 1 yard= ....m , 1yard=0.9144 m

7.a) describe in steps how would you measure the length of a pencil using a metre ruler .draw a diagram if necessary.

Ans. To measure the length of a pencil with a metre ruler the ruler is placed with its markings close to the pencil. Then the zero mark on the ruler is is made to coincide with one end of the pencil. Now the the position of the other end of the pencil is read on the ruler. This reading gives the length of the pencil.

Draw fig.2.2 of your physics book instead of rod you have to draw a pencil.

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

Ans. To measure the length of a pencil with a broken or a damaged ruler, the pencil is placed close to a specific marking on the ruler and positions of both end of the pencil are read on the ruler. The difference of the two reading gives the length of the pencil.

Draw fig. Similar to fig.2.3 in your physics copy.

8. Name the device which you will use to measure the perimeter of your playground. Describe in steps how you will use it.

Ans. Measuring tape  is the device which we will used to measure the Perimeter of our playground. First we measures the length and then breadth of the playground by using measuring tape. And then the  formula for  the perimeter of a rectangle to be used.

P= 2(l+b)

9. The diagram below shows a stick placed along a metre ruler. The length of the thick is measured keeping the eye at positions A,B andC.

a) write the length of check PQ as observed ,for each position of the eye. Are they all same?

Ans. At A=3.4 cm

At B=3.2cn

At C =3.0 cm.

They are not same.

b) which is the correct position of the eye? Write the correct length of the stick.

Ans. The correct position is  at A.

The correct length of the stick is 3.2 cm.

10. Define mass. State its a)S.I    b)C.G.S and

c) F.P.S units. How are they related?

Ans. Mass- the mass of a body is the quantity of matter contained in it.

a) S.I. unit is kg( kilogram).

b) C.G.S. unit is g( gram).

c)F.P.S. unit is lb( pound).

Relationship

1 g =1/1000 kg

       =10-³ kg

1 g = 0.0022 lb

1 lb =453.59 g

1 lb = 453.59 /1000 kg

        =0.45359 kg

1 kg= 1000g

1kg =1/0.45359 lb

        = 2.205 lb

11. Convert the the following quantities as indicated:

a)2500 kg = ...2.5....metric tonne                                 1 metric tonne = 1000 kg

1000 kg= 1 metric tonne

2.5 × 1000 kg = 2.5 × 1 metric tonne

2500 kg=2.5 metric tonne.

b)150 kg = ..1.5...... quintal

1 quintal = 100 kg

100 kg = 1 quintal

1.5 ×100 kg = 1.5 × 1 quintal

150 kg = 1.5 quintal

c) 10 lb = .....4.5359.. kg

1 lb =0.45359 kg

10× 1 lb =10 × 0.45359 kg

10 lb= 4.5359 kg.

d)2500 g= ...2.5...kg

1 g = 1/1000 kg

2500× 1g =2500 ×1/1000 kg

2500 g =2.5 kg

e)0.01 kg =....10.. g

1 kg = 1000 g

0.01 ×1 kg = 0.01 × 1000 g

0.01 kg = 10 g

f)5 mg =...... kg

1 mg = 10-⁶ kg

5 × 1 mg = 5× 10-⁶ kg

5 mg = 5 × 10-⁶ kg

1g = 10-³ kg

But 

1mg = 10-³ g

1mg = 10-³ ×1 g

1 mg = 10-³× 10-³ kg  (1g=10-³ kg)

1 mg = 10-³-³ kg

1mg = 10‐⁶ kg

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

Ans. Beam balance is the instrument which is commonly used to measure the mass of a body.

For measuring, The Beam balance is first held up. On holding up the balance, it is is noticed 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 bean is again Horizontal on holding the balance up. The total of the standard weight gives the mass of the given body.