Samacheer Class 7 Science - Measurement

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

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

S.No
Volume of liquid
Capacity of a container
1.
Volume is the amount of space taken up by a liquid
Capacity is the measure of an objects ability to hold a substance like solid, liquid or gas
2.
It is measured in cubic units.
It is measured in litres, gallons, pounds, etc.
3.
It is calculated by multiplying the length, width and height of an object.
It’s measurement is cc or ml.

One astronomical unit is defined as the average distance between the earth and the sun.
1 AU = 1.496 5 10 6 km = 1.496 × 10 11 m.

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+(\(\frac { 3 }{ 4 }\)) N + (\(\frac { 1 }{ 2 }\)) P+\(\frac { 1 }{ 4 }\) Qsq.cm
= 52 + 5.25 = 58.25 sq.mm = 0.5825 sq.cm

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 cm 3 .
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 cm 3
∴Volume of the solid = (60-40) cm 3
= 20 cm 3 = V cm 3 (assume)
Knowing the mass and the volume of the stone, the density can be calculate by the formula:

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.

Given radius = 10 cm = 0.1m
π= 3.14
Area of a circular disc A = ?
Formula : Area of a circle A = πr 2
= 3.14 × 0.1 × 0.1
A = 0.0314 m 2

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 m 2

Given : Density Copper Dc = 8900 kg/m 3
Density of Iron D 1 = 7800 kg/m 3
Volume of Copper sphere = Volume of Iron sphere
To find : Ratio of Masses of Copper (M C ) and Iron (M I )
Mass = Density x Volume
M C = D C x V, M 1 = D 1 x V
M C = 8900 V, M 1 = 7,800 V
M C = M 1
8900 V : 7800 V
= 1.14: 1

Given : Mass of a liquid M = 250 g
Volume V = l000cc
Density of the liquid D = ?

Density of the liquid = 0.25 g/cc

Given : radius of a sphere r = 1cm
Volume of the sphere V = ?
Mass of the sphere M = 33 g
Density of silver D = ?

Density of silver sphere = 7.889 g/cc.

1. A. A derived quantity
2. B. SI unit of volume
3. C. A liquid denser than iron
4. D. A unit of length used to measure very long distances

Clues – Across
1. KELVIN
2. VOLUME
3. DENSITY
4. CAPACITY
Clues – Down
a. VELOCITY
b. CUBIC METRE
c. MERCURY
d. LIGHT YEAR

V 1 = 30 cc, V 2 = 40 cc; Volume of stone =v 2 – v 1 = 40cc – 30cc = 10cc