9th Class Physics Notes “Conceptual Question”

CONCEPTUAL QUESTION

Q1: How technology is shaped by physics?

Ans: Physics and technology are closely related.

The technology is shaped by physics. It is because of the following reasons.

For Examples:

1. All the automobiles; Buses cars etc are all based on the principles of physics.
2. Computer is used in this modern technology which works on the principles of physics.
3. The discovery of laws of electromagnetic induction enabled the engineers to develop electric generator.
4. The discovery of nuclear fission led to the development of Nuclear power plant which produce huge amount of energy for use and research.  

Conclusion:

From the above a little discussion, it is clear that physics has played an important role in the development of various technologies.

Q2: Give some example of applications of work done by physics?

ANS:

Importance of physics:

Physics major role and contributed many services for humanity, by the invention some of the application which are done by physician are given below.

1. Discovery of electron:

The discovery of electron led the development of many electronic devices like T.V, Radio, Computer etc. which make our life easy.

2. Production of nuclear energy:

Production of nuclear energy form atom is a great work made by physics.

3. C.T scan:

With help of this invention which is made by physician, we are able to see the structure of head.

4. Electricity:

Electricity is the invention of physics without which we cannot run any mechanic.

5) Satellite:

A geostationary satellite which is revolving around earth a great work made by physics with help of this satellite we get information about weather and geographical survey.

6) Buses, vehicle and airplanes:

Buses, vehicle and airplane etc. is the invention of physics and with help of which we can easily travel from one place to another.

7) Radioactivity and X-rays:

The discovery of radioactivity and X-rays solve many problems in medical science. These rays are also used in industry and agriculture.

Q3: Why are measurements important?

Ans:

Importance of measurement:

Measurement helps us to know about the exact magnitude of the quantity. Physics deals with physical quantities. Physical quantities are those quantities which can be measured. Without measurement, we cannot imagine this world in working condition.

1. Without measurement, purchase and sale of vegetables, fruits, clothes, rice, sugar etc are impossible.
2. The working of labours in factories related to time which can be measured with the help of watch.
3. Construction of rooms and bathrooms in a house can be constructed by taking proper measurement in meters, foot, yard etc.
4. Experiments in laboratories can be performed by taking proper measurements.

Conclusion:

From the above discussion, it is clear that measurements are important and with our measurement life would become miserable for human beings.

Q4: Why area is called derived physical quantity?

ANS:

Area is derived physical quantity:

Area is derived physical quantity because its unit meter square is obtained by the unit of length i.e. meter twice.

A derived physical quantity is obtained by multiplying or dividing one base physical quantity with another base physical quantity. Also if base physical quantity unit occur more than once, it gives the derived physical quantity.

Area is obtained by multiply length and width in which unit of length i.e. meter occur twice so area is called derived physical quantity.

Mathematically:

Area = Length x width

unit of Length = meter unit of width = meter

Therefore

area = meter x meter area = meter^2

Conclusion:

From above discussion it is clear that unit of area is meter square, in which meter occur twice. Hence area is called derived physical quantity.

Q5: Name any four derived units and write them as their base unit?

Ans:

Derived unit:

The unit which is obtained by multiplying or dividing the base unit is called derived unit.

The unit of derived physical quantity is known as derived unit. For example, “meter/second” is the derived unit of speed. [Speed is derived quantity] some of the derived physical quantities and their units are given in the following table.  

S.No	Derived physical quantity	Unit of derived physical quantity	Symbol
01	Force	Newton = N	N = kg m/s^2
02	Work	Joule = J	J = N-m = kg m^2/s^2
03	Power	Watt = W	W = J/s = kg m^2/s^3
04	Pressure	Pascal = Pa	Pa = kg m^-1 s^-2
05	Speed	Meter/second = m/s	m/s
06	Electric charge	Coulomb = C	C = Ampere-second = A.S
07	Momentum, P = mv	kg m/s	kg m/s
08	Density	Kilogram per cubic meter	kg/m^3

Q6: Why in physics we need to write in scientific notation?

Ans: Use of scientific notation in physics:

With the help of scientific notation, we can express very large numbers or very small numbers very easily. We can express the number “N” in terms of a number “M” and power of 10. i.e, Scientific notation:

N = M x 10^n

Where “M” represent a number whose 1st digit is non-zero digit and “n” represent the power of 10, which may be positive or negative.

Example:

For example the radius of earth is 6400000m, is a large number, in terms of scientific notation we can write it as under 6400000 m = 6.4 x 10^6 m.

Q7: What is least count? How least count for vernier caliper and screw gauge are defined.

Ans: LEAST COUNT:

Definition:

The minimum length that can be measured by an instrument is known as its least count.

Least count of Vernier caliper:

Definition:

The minimum length hat can be found with the help of Vernier caliper is called the least count of Vernier caliper.

Mathematically:

Least count = Value of smallest division on main scale / total no of division on v.scale

=> L.C = 1/10 = 0.1 mm

In “cm”

L.C = 0.1/10 = 0.01 cm

Least count of screw gauge:

Definition:

The minimum length that can be measured by a screw gauge is known as its least count.

Mathematically:

Least count = 1mm/100

OR

L.C = 0.01 mm

“In Cm”

L.C = 0.001 cm

Q8: How can we find the volume of small pebble with help of measuring cylinder?

ANS:

To find volume of small pebble with help of measuring cylinder we use the following method.

Step 1:

Take a measuring cylinder and pure some water in it.

Step 2:

Note the level of water in cylinder. This is the initial volume of water i.e. Vi.

Step 3:

Now put a small pebble into the cylinder gently and note the volume of water. This is the final volume i.e. Vf.

Step 4:

Find the difference between the final volume and initial volume; this is the volume of small pebble.

volume of pebble = ΔV = final volume – initial volume volume of pebble = ΔV = Vf – Vi

Example:

Let we have a measuring cylinder when we put some water in it, the initial volume of water is 20ml. By putting a small pebble the volume of water increase and be 30ml.

Now the volume of small pebble can be found by subtracting initial from final volume i.e.

volume of small pebble = ΔV = Vf – Vi volume of small pebble = ΔV = 30 – 20 volume of small pebble = 10ml