Tamilnadu Samacheer Kalvi 7th Science Solutions Term 1 Chapter 1 Measurement

 

Tamilnadu Samacheer Kalvi 7th Science Solutions Term 1 Chapter 1 Measurement

Samacheer Kalvi 7th Science Measurement Textual Evaluation

BOOK EXERCISE

I. Choose the appropriate answer:

Question 1.

Which of the following is a derived unit?

(a) mass

(b) time

(c) area

(d) length

Answer:

(c) area

Question 2.

Which of the following is correct?

(a) 1L=lcc

(b) 1L= l0cc

(c) 1L= l00cc

(d) 1L= l000cc

Answer:

(d) 1L = 1000cc

Question 3.

SI unit of density is

(a) kg/m2

(b) kg/m3

(c) kg/m

(d) g/m3

Answer:

(b) kg/m3

Question 4.

Two spheres have equal mass and volume in the ratio 2:1. The ratio of their density is

(a) 1:2

(b) 2:1

(c) 4:1

(d) 1:4

Answer:

(b) 2:1

Question 5.

Light year is the unit of

(a) Distance

(b) time

(c) density

(d) both length and time

Answer:

(a) Distance

II. Fill in the blanks:

1.Volume of irregularly shaped objects are measured using the law of Archimedes

2.One cubic metre is equal to 10,00,000 or 1066  cubic centimetre.

3.Density of mercury is 13,600 kg/m3

4.One astronomical unit is equal to 1.496×1011m

5.The area of a leaf can be measured using a

graph sheet

III. State whether the following statements are true or false.

Question 1.

The region covered by the boundary of the plane figure is called its volume.

Answer: (False) Correct statement: The region covered by the boundary of plane figure is called its area.

Question 2.

Volume of liquids can be found using measuring containers.  Answer: True

Question 3.

Water is denser than kerosene.

Answer:

True

Question 4.

A ball of iron floats in mercury.

Answer:

True

Question 5.

A substance which contains less number of molecules per unit volume is said to be denser.

Answer: False.

Correct statement: A substance which contains more number of molecules per unit volume is said to be denser.

IV. Match the items in column – I to the items in column – II :

Question 1.

i. Area  (a)light year

ii.Distance  (b)m3

 iii.Density   (c)m2

iv.Volume   (d)kg

V.Mass   (e)kg/ m3

Question 2.

i.Area   (a)g / cm3

ii.Length   (b)measuring jar

 iii.Density   (c)amount of a substance

iv.Volume   (d)rope

V.Mass   (e)plane figures

V. Arrange the following in correct sequence :

Question 1.

1L, 100 cc, 10 L, 10 cc

Answer:

10 cc, 100 cc, 1L, 10L

Question 2.

Copper, Aluminium, Gold, Iron

Answer:

Aluminium, Iron, Copper, Gold

VI. Use the analogy to fill in the blank:

Question 1.

Area: M2 :: Volume : _________

Answer: M3

Question 2.

Liquid : Litre :: Solid : _________

Answer: cm3

Question 3.

Water: Kerosene :: ______ : Aluminium

Answer: Iron

VII. Assertion and reason type questions:

Mark the correct choice as

(a) Both assertion and reason are true and reason is the correct explanation of assertion

(b) Both assertion and reason are true, but reason is not the correct explanation of assertion

(c) If assertion is true but reason is false

(d) Assertion is false but reason is true

Question 1.

Assertion (A) : Volume of a stone is found using a measuring cylinder.

Reason (R) : Stone is an irregularly shaped object.

Answer:

(a) If both assertion and reason are true and reason is the correct explanation of assertion

Question 2.

Assertion (A) : Wood floats in water.

Reason (R) : Water is a transparent liquid.

Answer:

(b) If both assertion and reason are true, but reason is not the correct explanation of assertion

Correct explanation: Density of water is more than the density of wood.

Question 3.

Assertion (A) : Iron ball sinks in water.

Reason (R) : Water is denser than iron.

Answer:

(b) If both assertion and reason are true, but reason is not the correct explanation of assertion

Correct explanation : Density of iron is more than that of water.

VIII. Give very short answer:

Question 1.

Name some of the derived quantities.

Answer:

Area, volume, density.

Question 2.

Give the value of one light year.

Answer:

One light year = 9.46 x 1015m

Question 3.

Write down the formula used to find the volume of a cylinder.

Answer:

Volume of a cylinder = πr2 h

Question 4.

Give the formula to find the density of objects.

Answer:

Density = mass(m)

   volume(v)

Question 5.

Name the liquid in which an iron ball sinks.

Answer:

Iron ball sinks in water. The density of an iron ball is more than that of water so it sinks in water.

Question 6.

Name the unit used to measure the distance between celestial objects.

Answer:

Astronomical unit and light year are the units used to measure the distance between celestial objects.

Question 7.

What is the density of gold?

Answer:

Density of gold is 19,300 kg/m3

IX. Give Short Answer.

Question 1.

What are derived quantities?

Answer:

The physical quantities which can be obtained by multiplying, dividing or by mathematically combining the fundamental quantities are known as derived quantities.

(or)

The physical quantities which are expressed is terms of fundamental quantities are called

Question 2.

Distinguish between the volume of liquid and capacity of a container.

Volume of liquid    

1.Volume is the amount of space taken up by a liquid

 It is measured in cubic units

It is calculated by multiplying the length, width and height of an object.

Capacity of a container

Capacity is the measure of an objects ability to hold a substance like solid, liquid or gas

It is measured in litres, gallons, pounds,etc.,

 It’s measurement is cc or ml

Question 3.

Define the density of objects.

Answer:

Density of a substance is defined as the mass of the substance contained in unit volume

Question 4.

What is one light year?

Answer:

One light year is the distance travelled by light in vacuum during the period of one year.

1 Light year = 9.46 x 1015m.

Question 5.

Define one astronomical unit?

Answer:

One astronomical unit is defined as the average distance between the earth and the sun.

1 AU = 1.496 5 106km = 1.496 × 1011m.

X. Answer In detail.

Question 1.

Describe the graphical method to find the area of an irregularly shaped plane figure.

Answer:

To find the area of an irregularly shaped plane figure, we have to use graph paper.

Place a piece of paper with an irregular shape on a graph paper and draw its outline.

To find the area enclosed by the outline, count the number of squares inside it (M).

You will find that some squares lie partially inside the outline.

Count a square only if half (p) or more of it (N) lies inside the outline.

Finally count the number of squares, that are less than half. Let it be

For the shape in figure we have the following:

M = 50

N = 7

P = 4

Q = 4

Now, the approximate area of the can be calculated using the following formula.

Area of the leaf = M+(3/4) N + (1/2) P+1/4 Qsq.cm

= 52 + 5.25 = 58.25 sq.mm = 0.5825 sq.cm

Question 2.

How will you determine the density of a stone using a measuring jar?

Answer:

Determination of density of a stone using a measuring cylinder.

In order to determine the density of a solid, we must know the mass and volume of the stone.

The mass of the stone is determined by a physical balance very accurately. Let it be ‘m’ grams.

In order to find the volume, take a measuring cylinder and pour in it some water.

Record the volume of water from the graduations marked on measuring cylinder. Let it be 40 cm3.

Now tie the given stone to a fine thread and lower it gently in the measuring cylinder, such that it is completely immersed in water.

Record the new level of water. Let it be 60 cm3

∴Volume of the solid = (60-40) cm3

= 20 cm3 = V cm3 (assume)

Knowing the mass and the volume of the stone, the density can be calculate by the formula:  

Density   = Mass

  Volume

XI. Questions based on Higher er Thinking skills:

Question 1.

There are three spheres A, B, C as shown below :

Answer:

Sphere A and B are made of the same material. Sphere C is made of a different material. Spheres A and C have equal radii. The radius of sphere B is half that of A. Density of A is double that of C.

Question 2.

Now answer the following questions:

Find the ratio of masses of spheres A and B.

Find the ratio of volumes of spheres A and B.

Find the ratio of masses of spheres A and C.

Answer:

i. Ratio of masses of spheres A and B

MA : MB

D × VA : D × VB

Let the mass of sphere A = MA

Let the mass of sphere B = MB

Mass = Density × Volume

MA = DA × VA

MB = DB × VB (Density is same)

Volume of Sphere A =4/3πr3

ii. Ratio of volumes of spheres A and B

VA : VB

8 : 1 (As mass is directly proportional to volume)

iii. Ratio of masses of spheres A and C.

[∴ Density of A is double that of C ]

XII. Numerical problems:

Question 1.

A circular disc has a radius 10 cm. Find the area of the disc in m2. (Use n = 3.14)

Answer:

Given radius = 10 cm = 0.1m

π= 3.14

Area of a circular disc A = ?

Formula : Area of a circle A = πr2

= 3.14 × 0.1 × 0.1

Solution : A = 0.0314 m2

Question 2.

The dimension of a school playground is 800 m x 500 m. Find the area of the ground.

Answer:

Given :The dimension of a school

Playground = l x b = 800 m x 500 m

Formula :Area of the ground A = l x b

= 800 x 500 = 4,00,000

A = 4,00,000 m2

Question 3.

Two spheres of same size are made from copper and iron respectively. Find the ratio between their masses. Density of copper 8,900 kg/m and iron 7,800 kg/m3

Answer:

Given : Density Copper Dc = 8900 kg/m3

Density of Iron D1 = 7800 kg/m3

Volume of Copper sphere = Volume of Iron sphere

To find : Ratio of Masses of Copper (MC) and Iron (MI)

Solution: Mass = Density x Volume

MC = DC x V, M1 = D1 x V

MC = 8900 V, M1 = 7,800 V

MC = M1

8900 V : 7800 V

= 1.14: 1

Question 4.

A liquid having a mass of 250 g fills a space of lOOOcc. Find the density of the liquid.

Answer:

Given : Mass of a liquid M = 250 g

Volume V = l000cc

Density of the liquid D = ?

Solution: Density of the liquid = 0.25 g/cc

Question 5.

A sphere of radius 1cm is made from silver. If the mass of the sphere is 33 g, find the density of silver (Take π = 3.14)

Answer:

Given : radius of a sphere r = 1cm

Volume of the sphere V = ?

Mass of the sphere M = 33 g

Density of silver D = ?

Solution: Density of silver sphere = 7.889 g/cc.

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