UHA Physics Notes 9th Class

          Chapter-1

 Important short Question: 

1. Define Physics?

Ans:

The study of matter, energy and their interaction is called physics. The law and principals of physics help us to understand nature.

2. What is plasma physics?

Ans:

It is study of production, properties of the ionic state of matter - the fourth state of matter.

3.What is physical quantities? write the name of its types.

Ans:

All measurable quantities are called physical quantities such as length, mass, time and temperature. 

Name of its type are given bellow 

Base quantities 

Derived quantities

4.Define Geophysics?

Ans:

It is the study of the internal structure of the Earth.

5. Define base quantity and derived quantity? 

OR

Difference between base quantity and derived quantity?

Ans:

Base quantities:

Base quantity are the quantities on the basis of which other quantities are expressed are called base quantities. These are length, mass, time, electric current, temperature, intensity of light, and the amount of substance.

Derived quantities:

Those quantities that are expressed in terms of base quantities these are called derived quantities. These include area, volume, force, speed, force, work, energy, power, electric charge, electric potential, etc.

6.What is unit?

Ans:

Once a standard is set for a quantity then it can expressed in terms of that standard quantity. This standard quantity is called a unit.

7.What is International System of Units?

Ans:

The eleventh general conference on Weight and Measures held in Paris in 1960 adopted a world wide system of measurement called  international system unit. The international system of Unit is commonly referred as SI .

8.Define base units and derived units?

OR

Difference between base units and derived units?

Ans;

Base units:

The unit that describe base quantity are called base unit. Each base quantity has its SI unit. For example, length, mass, time.

Derived units:

The units use to measure derived quantity are called derived units. For example, area, volume, force, power.

9.Define prefixes and give its example?

Ans:

Some of the quantity are either very large or very small. For example, 250000 m, 0.002 W and 0.000 002 g etc. Prefixes are the words or letters added before SI Units such as kilo, mega, giga, and milli.

10.What is Scientific notation and give example?

Ans:

In scientific notation a number is expressed as some power of ten multiplied by a number between 1 and 10. For example, a  number 62.750 can be expressed as 62.75× 103 or 6.275× 104 or 0.6275× 105.

11.What is electricity and Magnetism?

Ans:

It is the study of the charges at rest and in motion, their effects and their relationship with magnetism.

12.Define Vernier caliper?

Ans:

An instrument used to measure small lengths such as internal or external diameter or length of a cylinder, etc. is called as Vernier Calipers.

13.What is least count of Vernier Caliper?

Ans:

The difference between one small division on main scale division and one Vernier scale division is 0.1 mm. It is called least count (LC) of the Vernier calipers.

Formula of Vernier caliper is given bellow:

Least account of

 Vernier calipers  = smallest reading on main scale /no. of division on Vernier scale

  =  1mm/10 divisions           =      0.1 mm

Hence                    LC = 0.1 mm              = 0.01 cm

14. How can I check the zero error and zero correction?

Ans:

If zero line of the Vernier scale coincides with the zero of the main scale then the zero error is zero . Zero error will exist if zero line of the Vernier scale is not coinciding with the zero of main scale. Zero error will be positive if zero line of Vernier scale is on the right side of the zero of the main scale and will be negative if zero line of Vernier scale is on the left side of zero of the main scale. 

15. Define screw gauge?

Ans:

A screw gauge is an instrument that is used to measure small lengths with accuracy greater than a Vernier Caliper. It is also called as micrometer screw gauge.

16. What is the pitch of screw gauge?

Ans:

The hollow cylinder act as a nut. It is fixed at the end of U-shaped frame opposite to the stud. A thimble has a threaded spindle inside it. As the thimble completes one rotation, the spindle moves 1 mm along the index line. It is because the distance between consecutive threads on the spindle is 1 mm. This distance is called the pitch of screw on the spindle.

17.What is the least account of screw gauge?

Ans:

The thimble has 100 divisions around its one end. It is the circular scale of the screw gauge. As thimble completes one rotation, 100 divisions pass the index line and thimble moves 1 mm along the main scale. Thus each division of circular scale crossing the index line moves the thimble through 1/100 mm or 0.01 mm on the main scale. Least count of a screw gauge can also be found as given below:

least count = pitch of the screw gauge / no. of division on circular scale

18. Find the positive and negative zero error of screw gauge?

Ans:

Positive zero error:

Zero error will be positive if zero of circular scale is behind the index line. In this case, multiply the number of divisions of the circular scale that has not crossed the index line with the least count of screw gauge.

Negative zero error:

Zero error will be negative if zero  of circular scale has crossed the index line. In this case multiply the number of divisions of circular scale  that has crossed the index line with the least count of screw gauge.

19.Write the name types of stopwatch?

Ans:

There are two types of stopwatch these are given bellow:

• Mechanical stopwatch 
• Digital stopwatch

20.What is sound?

Ans:

It deals with the physical aspects of sound waves, their production, properties and applications.

21. Define significant figures and give its examples?

Ans:

Significant figures:

All the accurately known digits and the first doubtful digit in an expression are called significant figures.

Example:

A student measured the length of a book as 18 cm using a measuring tape. The numbers of significant figures in his/her measured value are two. The left digit is 1 the accurately known digit. While the digit 8 is the doubtful digit for which the student may not be sure.

22.Define meter rule?

Ans:

A meter rule is a length measuring instrument. It is commonly used in the laboratories to measure length of an object or distance between two points.

23. What is beam balance?

Ans:

A sensitive beam balance may be able to detect a change as small as of 0.1 g or 100 mg.

24. What is physical balance?

Ans:

Least count of the physical balance may be as small as 0.01g or 10mg. Therefore, its measurement would be more precise than a sensitive beam balance.

25.What is electronic balance?

Ans:

Least count of an electronic balance is 0.001 g or 1mg.Therefore, its measurement would be more precise than a sensitive physical balance.

26. what is stopwatch?

Ans:

A stopwatch is used to measure the time interval of an event. Mechanical stopwatches have least count up to 0.1 seconds. Digital stopwatch of least count 0.01s are common.

27. What is measuring cylinder?

Ans:

A measuring cylinder is a glass or transparent plastic cylinder. It has a scale along its length that indicates the volume in milliliter (mL). They are used to measured the volume of a liquid or powdered substance.

28. What is nuclear physics?

Ans:

Nuclear physics deals with the properties and behavior of nuclei and the particles within the nuclei.

29.Define atomic physics?

Ans?

The study of the structure and properties of atoms is called atomic physics.

30.Calculate your 14 years age in seconds?💝

Solution:

       Total days in one year =365 

         1 day = 24 hours

          1 hour = 60 min

          1 min = 60 sec

In 1 hour the number of seconds = 60*60 =3600 sec

In 1 day the number of seconds = 24*3600 = 86,400 sec 

In 1 year the number of seconds = 365* 86400 = 31,536,000 sec

in 14 year the number of seconds = 14*31,536,000 = 441,504,000 sec

Exercise 

 1. Circle the correct answer from the given choices.

i. The number of base units in SI are:

a) 3      b)  6      c)  7        d)9

ii. Which one of the following unit is not derived unit?

a) Pascal          b) kilogram's          c) newton          d) watt

iii. Amount of a substance in terms of numbers is measured in:

a) gram          b) kilograms          c) newton          d)mole

iv. An interval of 200μs is equivalent to 

a) 0.2 s          b) 0.02 s          c) 2× 10-4 s          d) 2× 10-6 s

v. Which one of the following is the smallest quantity?

a) 0.01 g          b) 2 mg          c) 100 μg          d) 5000 ng

vi. Which instrument is most suitable to measure the internal diameter of a test tube?

a) meter rule     b) Vernier Caliper     c) measuring tap     d) screw gauge

vii. A student claimed the diameter of a wire as 1.032 cm using Vernier Calipers. Up to what extent do you agree with it?

a) 1 cm          b) 1.0 cm          c) 1.03 cm          d) 1.032 cm

viii. A measuring cylinder is used to measure:

a) mass          b) area          c) volume          d) level of a liquid 

ix. A student noted the thickness of a glass sheet using a screw gauge. On the main scale, it reads 3 divisions while 8th division on the circular scale coincides with index line. Its thickness is:

a) 3.8 cm          b) 3.8 mm          c) 3.08 mm          d) 3.08 m

x. Significant figures  in an expression are :

a) all the digits                                          

b) all the accurately known digits       

c) all the accurately known digits and the first doubtful digit

d)  all the accurately known and all the doubtful digits

i	ii	iii	iv	v	vi	vii	viii	ix	x
c	b	d	c	d	b	c	c	c	c

1.2 What is difference between base quantities and derived quantities? Give three examples in each case.

Ans: (See short Question 3)

1.3 Pick out the base units in the following:

Ans: 

Kilogram(unit of mass)

Mole(unit of quantity of substance

Ampere(unit of electric current)

Meter(unit of length)

 Kelvin(unit of temperature)

1.4 Find the base quantities involved in each of the following derived quantities:

Ans: 

speed= distance/time

       =length/time

volume=length*width*height

           = length*length*length

Force = mass*acceleration

         = mass* Change in velocity/ time

         =mass*distance/time*time

         =mass*length/time*time

work=Force*distance

       =mass*acceleration*distance

1.5 Estimate your age in seconds.

Ans: (See short Question number 30)

1.6 What role SI units have played in the development of science?

Ans:

1.7 What is meant by Vernier constant?

Ans:

1.8 What do you understand by to zero error of a measuring instrument?

Ans:

1.9 Why is the use of zero error necessary in a measuring instrument?

Ans:(See sort Question 14)

1.10 What is stop watch ? what is the least count of mechanical stopwatch you have used in the laboratories?

Ans: 

1.11 Why do we need to measure extremely small interval of times? 

Ans:

1.12 What is meant by significant figures of a measurement?

Ans:(See short Question 21)

1.13 How is precision related to the significant  figures in a measured quantity?

Ans:

   PROBLEMS 

1.1 Express the following quantities using prefixes.

a) 5000 g         5kg

b) 2000000 W   2MW

c) 52 kg            5.2× 10-10 μg

d) 225 s            2.25× 10-8 μs

1.2 How do the prefixes micro, nano and pico relate to each other?

Solution:

1.3 Your hair grow at the rate of 1mm per day. Find their growth rate in nm per sec.

Solution:

1.4 Rewrite the following in standard form.

a) 1168× 10-27            1.168 

b) 32× 105               3.2

c) 725 × 10-5    kg      7.25

d) 0.02 × 10-8            2

1.5 Write the following quantities in standard form.

a) 6400 km                           6.4× 103 km

b) 380 000 km                       3.8× 105  km

c) 300 000 000 m s-1                 3× 108 m s-1

d) seconds in a day                 8.64× 104  s

1.6 On the closing the jaws of a Vernier Calipers, zero of the Vernier scale is on the right to its main scale such that 4th division of its Vernier scale coincides with one of the main scale division. Find its zero error and zero correction.

Solution:

1.7 A screw gauge has 50 divisions on its circular scale. The pitch of the screw gauge is 0.5 mm. What is its least count?

Solution:

1.8 Which of the following quantities have three significant figures?

a) 3.0066 m

b) 0.00309 kg                    Ans

c) 5.05× 10-27 kg             Ans

d) 301.0 s

1.9 What is the significant figures in the following measurements?

a) 1.009 m                      4

b) 0.00450 kg                   3

c) 1.66× 10-27 kg            3

d) 2001 s                         4

1.10 A chocolate wrapper is 6.7  cm long and 5.4 cm wide. Calculate its area up to reasonable number of significant figures.

Solution: