2272180-chapter-1-introduction-to-physics

8/7/2019 2272180-Chapter-1-Introduction-to-Physics

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Physics Module Form 4

Chapter 1 : Introduction To Physics

_________________________________________________________________________________________

CHAPTER 1 : INTRODUCTION TO PHYSICS

1.1 Understanding Physics

By the end of this subtopic, you will be able to

Explain what physics is,

Recognise the physics in everyday objects and in natural phenomena.

What is physics ?

The word Physics is originated from the Greek word physikos.

In physics, we study natural phenomena and the properties of matter. The aim of physics is to

explain the fundamental nature of the universe by using the concept of physics.

Physics involves the conduct of studies and experiments to find anwers to the question Why?

and How? in relation to the mysteries of the universe.

The majority of natural phenomena can be explained using the principles of physics, for example

;i) We cannot see an object behind a wall because light travels in a straight line.

ii) The image of the pencil formed by the mirror is due to the reflection of light.

Fields of study in physics

The scope of physics very wide. Knowledge of physics is grouped into different fields of study as

shown in figure 1.1.

1

Mechanical Energy

Fields ofstudy inphysics

Heat

- Studies the

influence of heat ondifferent types of

matter.

Electronics

- studies the use of

electronic devices in

Force and motion- investigates the

action of force and

motion

Forces and pressure

- pressure, pressure in liquids, gaspressure, atmospheric pressure,

Pascals principle, Archimedes

principle, Bernoullis principle.

Light- explains the

different

phenomenon due

to light.

Waves

- understands the properties

of different types of waves

and their uses.

Electricity and

electromagnetism

- investigates theinteractions of electric

and magnetic fields.

Electricity andelectromagnetism

- investigates the

interactions of electric

and magnetic fields


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1.2 PHYSICAL QUANTITIES

Base quantity

1 A physical quantity is ..

2. List examples of physical quantities in the box.

3.The value of the measurements consists of a numerical magnitude and a unit.

example : the length of a metre rule is 250 cm

4. Physical quantities are categorized into base quantities and derived quantities.

5. Base quantities are physical quantities that cannot be defined in terms of other physical

quantities.

6. There are five base quantities ; length, mass, time, current and temperature

Base quantity Symbol S.I. Unit Symbol for S.I. Unit

Length

Mass

Time

CurrentTemperature

Derived quantities

2

The list of physical quantities :

1. .

2. .

3. .

4. .

5. .

6. .

7. .8. .

batterybattery

physical

numerical

unit


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1 A derived quantity is .

2 Determine the derived unit for the following derived quantities.

Derivedquantity

Formula Derived unit Name ofderived unit

area area = length x width m x m = m2

volume volume = length x width x heightm x m x m =

m3

densityvolume

massensityd =

velocity

time

ntdisplacemeelocityv =

momentum momentum = mass x velocity kg m s-1

Accelerationtime

velocityinchangeonaccelerati =

Force force = mass x acceleration kg m s-2 Newton (N)

pressurearea

forcepressure=

weight weight = mass x gravitationalacceleration

work work = force x displacement

powertime

workpower=

kinetic

energy2velocitymassK.E =

2

1

potential

energy

P.E = mass x gravitational acceleration

x height Kg ms-2

Joule (J)

charge charge = current x time Ampere second

(As)Coulomb (C)

Standard Form

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1 Standard form = A x 10n , 1 < A < 10 and n = integer

2 Standard form is used to ...

3 Some physical quantities have extremely small magnitudes. Write the following quantities in

standard form :

a. Radius of the earth = 6 370 000 m =.

b. Mass of an electron = 0.000 000 000 000 000 000 000 000 000 000 911 kg =...

c. Size of a particle = 0.000 03 m =

b. Diameter of an atom = 0.000 000 072 m = ...

c. Wavelength of light = 0.000 000 55 m = ..

Prefixes

1. Prefixes are usually used to ...2. It will be written

3. The list of prefixes :

4. Some physical quantities have extremely large magnitudes. These extremely large and small

values can be written in standard form or using standard prefixes. Write the quantities in

standard prefixes:

a. Frequency of radio wave = 91 000 000 Hz = .

b. Diameter of the earth = 12 800 000 m =

c. Distance between the moon and the earth = 383 000 000 m =

d. Mass of the earth = 6 000 000 000 000 000 000 000 000 kg =

1.3 SCALAR AND VECTOR QUANTITIES

4

Tera (T)

Giga (G)

Mega (M)

kilo (k)

mili (m)

micro ()

nano (n)

pico (p)

1012

109

106

103

100

10-3

10-6

10-9

10-12

Hekto (ha)Deka (da)

desi (d)centi (s)

102

101

10-1

10-2

Eg :

1 Tm = .

3.6 mA = .

How to change the unit ;

Eg :

1. Mega to nano

2. Tera to micro

3. piko to Mega


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1 Scalar quantities are

Examples :

2 Vector quantities are...

Examples :

3 Study the following description of events carefully and then decide which events require

magnitude, direction or both to specify them.

Description of events Magnitude Direction

1. The temperature in the room is 25 0C

2. The location of Ayer Hitam is 60 km to the north-

west of Johor Bahru

3. The power of the electric bulb is 80 W

4. A car is travelling at 80 km h-1 from Johor Bahru

to Kuala Lumpur

Some common examples of scalar and vector quantities.

1.4 UNDERSTANDING MEASUREMENTS

1.Using appropriate instruments to measure.

5

Scalar quantities

.

.

Vector quantities

.


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When we measure a physical quantity, we need to consider its magnitude and then choose a

suitable instrument.

The magnitude of the quantity should not exceed the maximum capacity of the instrument, and

the instrument must be sensitive enough to detect and give a meaningful measurement of the

quantity.

For example; metre rule is used to measure the length of a book, measuring tape is used to

measure the length of a table and micrometer screw gauge is used to measure the diameter of a

glass rod.

. Example of measuring instruments :

1 Ammeter is used to measure ..

.2Measuring cylinder is used to measure ....................

3 A ruler is used to measure

wrong right wrong

10 11 12 13 14 1

Vernier Caliper

A vernier caliper is used to measure a small object with dimension up to 12 cm It is has an accuracy / sensivity of 0.01 cm

6

pointer mirrorpointer mirror

Pointers image is behind the pointer

incorrect reading correct

reading

1 2 3

0 4

1 2 30 4

Pointers image can be seen

Right position of eye (eye are in a line perpendicular to the plane of

the scale)

wrong position of eye

wrong position of eye

water


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There are two pair of jaws, one is designated to measure linear and outer diameters while

the other is to measure inner diameter

A vernier caliper consists of two steel bar scales, one sliding over the other.

i) The main scale is graduated in intervals of0.1 cm.ii) The sliding vernier scale has a scale on which ten divisions are equal to nine small

divisions on the main scale

(0. 09cm)

iii) The difference between the sizes of one division on the main scale and one division on

the vernier scale is

0.1 0.09 = 0.01 cm

giving a vernier scale an accurancy of0.01 cm.

Figure 1.3 : Ten divisions on the vernier scale are equal to nine small divisions on the main

scale.

HOW TO READ THE VERNIER CALLIPHERS.

The diagram below shows a vernier calliper with reading.

7

0 1 2 3 4 5 6 7 8 9 10

0 1 cm

Main scale = .

Vernier scale = ..

Caliper reading = main scale reading + (0.01 cm x vernier scale )=....................

Find the division ofvernier scale which iscoincides with any part ofthe main scale


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Vernier calliper reading = . cm

ZERO ERROR OF VERNIER CALLIPHERS

i) No zero error.

the 0 mark on the main scale is exactly in line with the 0 mark on the vernier scale when

the vernier caliper is fully closed.

ii) Positive zero error

the vernier scale is at distance to the right of the 0 mark on the main scale when vernier

caliper is fully closed.

This error is positive zero error = + 0.04 cm

iii) Negative zero error

the vernier scale is at distance to the left of the 0 mark on the main scale when vernier

caliper is fully closed.

This error is negative zero error = - ( 0.1 0.08 )

= - 0.02 cm

Micrometer screw gauge

8

0 5 10

0 1


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A micrometer srew gauge is used to measure a small lengths ranging between 0.10 mm and

25.00 mm.

Examples; can measure diameters of wires and thicknesses of steel plate.

It is has an accuracy/sensivity of 0.01 mm

Figure 1.5 : Micrometer screw gauge

The micrometer scale comprises a main scale marked on the sleeve and a scale marked on the

thimble called the thimble scale.

Each division on main scale is 0.5 mm.

The timble scale is subdivided into 50 equal divisions. When the thimble is rotated through one

complete turn, the main scale will moved to 0.5 mm.

This means that one division on the thimble scale is 0.50 mm = 0.01 mm

50 divisions

The reading of the micrometer screw gauge = main scale reading + ( 0.01 mm x thimble

scale )

When taking a reading, the thimble is turned until the object is gripped very gently between the

anvil and the spindle.

The ratchet knob is then turned until a click sound is heard.

The ratchet knob is used to prevent the user from exerting undue pressure.

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HOW TO READ THE MICROMETER SCREW GAUGE

1. Main scale reading= 2.0 mm.2. The reading on the thimble scale = 22nd mark on the thimble scale.

3. The final reading of the gauge is = 2.0 mm + ( 0.01 x 22) mm

= 2.22 mm.

ZERO ERROR

The accuracy of the micrometer screw gauge is also affected by zero error. Before

commencing determine the zero error and if had, it must to eliminate;

Correct reading = gauge reading zero error.

i) No zero error

the 0 mark on the thimble scale is exactly in line with the horizontal reference line on

the main scale when the micrometer is fully closed.

ii) Positive zero error

the horizontal reference line in the main scale is in line on the positive side of the 0

mark, on the thimble scale. The positive error reading is = + 0.04 mm

iii) Negative zero error

the horizontal reference line on the main scale is in line below the 0 mark of the

thimble scale.

The negative error reading is = 0.03 mm.

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Exercise: Vernier Callipers And Micrometer Screw Gauge

1. Write down the readings shown by the following

(a)

(b)

(c)

(d)

2. (a) The following diagram shows the scale of a vernier calliper when the jaws are closed.

Zero error = cm

11

0 5 10

0 1

0 5 1

6 7

0 5 10

7 8

0 5 10

4 5A B

QP

0 5 10

0 1

Answer: ..

Answer: ..

Answer: ..

Answer: 0..


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(b). The following diagram shows the scale of the same vernier calliper when there are

40 pieces of cardboard between the jaws.

3. Write down the readings shown by the following micrometer screw gauges.(a) (b)

Answer: . Answer:..

(c) (d)

Answer: Answer:.

4. (a) Determine the readings of the following micrometer screw gauges.

Zero error = .. mm Zero error = ........ mm

12

0 5 10

5 6

Reading shown = 5.64.cm

Corrected reading = 5.62..cm

35

400 5

3

0 5 103

20

250

0 0

45

5

0

0

15

200 5


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(b) Determine the readings of the following micrometer screw gauges.

5. Write down the readings shown by the following micrometer screw gauges.

(a) (b)

Answer: Answer: ........

(c) (d)

Answer: Answer:

6. (a) Determine the readings of the following micrometer screw gauges.

Zero error = ...............mm Zero error = .............. mm

(b) Determine the readings of the following micrometer screw gauges.

13

5

0

0 5

15

20

Zero error = 0.03mm Reading shown = 6.67..mm

Corrected reading = 6.64..mm

35

400 5

3

0 5 103

20

250

0 0

45

5

0

0

5

0

0 5

15

20

15

200 5

Zero error = 0.03.mm Reading shown = .6.67..mm

Corrected reading = 6.64..mm


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Accuracy , consistency and sensitivity in measurements.

1. Accuracy :

.....................................................................................................................................................

2. Consistency :

.....................................................................................................................................................

3. Sensitivity :

.......................................................................................................................................................

4. The diagram shows the result for four shooters A, B , C and D in a tournament. Every shooters

shot five times .

The table shows the conclusion .

Shooter Consistency AccuracyA High Low

B Low High

C High High

D Low Low

EXAMPLES OF MEASURING INSTRUMENTS AND THEIR ACCURACY.

1.

Mechanical stop watch

Accuracy : ..

2.

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Electronic stop watch

Accuracy :

Reading :.

3.Measurement Current

Ammeter range 0 5A

Accuracy :.

Double-scale ammeter

Accuracy of upper scale :..

Acuracy of lower scale : .

Reading :..

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Miliammeter range 0- 50 mA

Accuracy:

Reading :..

Accuracy:

Measurement Temperature

Accuracy:..

Measurement of Length

We normally use ruler, measuring tape , vernier calipers or micrometer screw gauge to measure

length.

Measuring

instrument

Smallest scale

division

Ruler 0.1 cm or

1 mm

Vernier

calipers

0.01cm

Mikrometer

screw gauge

0.01 mm

16

The smallest scale division on the measuring

instruments shows the sensitivity of the instruments.

Thus the more sensitive the measuring instruments thesmaller the scale divisions .

Therefore the micrometer screw gauge has the

highest sensitivity


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Errors in measurements

Any measurement of a physical quantity has errors or uncertainty.

Two main types of errors:

(i) (ii) ....................................................

Causes of Systematic Errors:

(i) .......................................................................................................................................

(ii) .......................................................................................................................................

Causes of Random Errors :

a)

b)

c)

SCIENTIFIC INVESTIGATIONS :

1. In this section you are required plan an experiment based on the scenario given .

2. To answer this section, students must be able to

Identify Responding Variable (RV) and Manipulated Variable (MV).

Relate the Responding Variable (RV)and Manipulated Variable (MV).

The table below provides the technique to answer questions in this section

STEPS REMARK FORMAT SAMPLE ANSWER

1.Making

observation

to identify

RV

And MV

RV and MV must be the

physical quantities that

can be measured during

the experiment.

RV: acceleration of the boat

MV: The total mass of the

boat

2. Inference An inference is a

conclusion drawn from

observation of a

phenomenon studied

RV depends on MV

OR

MV influences RV

(a)

Acceleration of the boat

decreases when its mass

is increased. OR Acceleration of the boat

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depends on the total mass

of the boat

3. Hypothesis

General statement that

assumed to be true

regarding the relationship

between MV and RV

(Must have

DIRECTION) based on

the experiment being

planned.

The longer/bigger theMV the longer/smaller

the RV

(b)

For a constant external forceacting on an object, the

bigger the mass of the object,

the smaller is its acceleration.

4. AimTo find the relationship

between MV and RV

To find the relationship

between the MV and

the RV

(c)(i)

To find the relationship

between acceleration and the

mass of an object.

5. Variable

Manipulated

Variable (MV) Physical Quantity

which is controlled /

changed for the

purpose of

investigating the

results of an

experiment..

Responding

Variable (RV)

Physical Quantitiy

which is the result ofthe changes made to

MV

Constant Variable

(CV) Physical

Quantities which are

kept constant during

the experiment

List down the:

Manipulated

Variable (MV)

Responding

Variable (RV)

Constant Variable

(CV)

that are used in the

experiment

(C)(ii)

Manipulated variable

(MV): mass of the

object, m

Responding variable

(RV): acceleration of the

object, a

Fixed variable (FV):

force acting on the

object, F

6. Equipment

or

Apparatus

List all apparatus and

materials used (the

apparatus that are used

to measure the RV and

MV must be included)

List all apparatus and

materials used

(C)(iii)

Ticker tape, cellophane tape,

three identical elastic

cords/rubber bands, ticker

timer, three trolleys, two

retort stand with clamps as

support, power supply,

runway for trolley.

7. Diagram Draw the correct diagram Draw the correct

diagram

(C)(iv)

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8. Procedure

Write in passive form

past tense.

The procedures must

include:

o Method of

measuring the first

value of MV.

o Method ofmeasuring the RV

o Repetition of

experiments using at

least another 4 MV

Write down the

procedures

(C)( v)

(i) The apparatus is set

up as shown in the

figure.

(ii) the ticker timer

which is connected

to the 12 V a.c.

power supply is

started and the

trolley is pulled

down the

runway.The elastic

cord is always

maintained at the

same length and

parallel with the

trolley.

(iii) The ticker obtained

is cut into 5-tick

strips and a tapechart for the motion

of the trolley is

made. The

acceleration of the

trolley, a, is

calculated and

recorded.

(iv) The steps are

repeated with 2 and

then 3 identical

trolleys stacked up.For each case, the

elastic cord is kept

stretched until the

end of the runway.

9. Tabulation

of data

Draw the basic table to

record data

Draw table to record

data

(C)(vi)

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10. Analysis

of data

Sketch the graph with

suitable quantities.

(vii)

the graph of acceleration, a

against m (or a against 1/m)

is plotted.

(1 point will be given for

EITHER

(a) writing: the graph ofa

against m (ora against 1/m)is plotted , or

(b) any of these graph

sketches. ALL labels must be

present.)

20

Normally must have

a minimum of 5

trials/data

Mass, m /

number of

trolley

1/

m

Accele

ration,

a / cm

s-2

1

2

3

4

5


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Plan and report an experiment

Situation : A few children are playing on a different length of swing in a playground. It is

found that the time of oscillation for each swing is different.

Steps Example : refer to the situation above

1 Inference

2 Hypothesis

3 Aim

4 Variables

5 List of

apparatus and

materials

6 Arrangement of

the apparatus

7 Procedures

8 Tabulate the

data

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9

1

0

11

Analyse the

data

Discussion

Conclusion

22

Precautions :1. Oscillation time is measured when the pendulum attained a steady

state.2. Time for 10 oscillations is repeated twice to increase accuracy.3. Discussion (refer to given questions)

The period increases when the length of the pendulum increases.Hypothesis accepted.


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Reinforcement Chapter 1

Part A :Objective Question

1. Which of the following is a base SI

quantity?

A Weight B Energy

C Velocity D Mass

2. Which of the following is a derived

quantity?

A Length B Mass

C Temperature D Voltage

3. Which of the following is not a basicunit?

A Newton B kilogram

C ampere D second

4. Which of the following quantities

cannot be derived?

A Electric current B Power

C Momentum D Force

5. Which of the following quantities is

not derived from the basic physical

quantity of length?

A Electric charge B Density

C Velocity D Volume

6. Initial velocity u, final velocity v,

time t and another physical quantity k

is related by the equation v - u = kt.

The unit for k is

A m s-1 B m-1 s

C m s-2

D m2

s-2

7. Which of the following has the

smallest magnitude?

A megametre B centimetre

C kilometre D mikrometre

8. 4 328 000 000 mm in standard form is

A 4.328 x 10-9 m B 4.328 x 10-6 m

C 4.328 x 106 m D 4.328 x 109 m

9. Which of the following measurementsis the longest?

A 1.2 x 10-5 cm B 120 x 10-4 dmC 0.12 mm D 1.2 x 10-11 km

10. The diameter of a particle is 250 m.

What is its diameter in cm?

A 2.5 x 10-2 B 2.5 x 10-4

C 2.5 x 10-6 D 2.5 x 10-8

11. Which of the following prefixes is

arranged in ascending order?

A mili, senti, mikro, desi

B mikro, mili, senti, desi

C mili, mikro, desi, senti

D desi, mikro, mili, senti

12. Velocity, density, force and energy are

A basic quantities

B scalar quantities

C derived quantities

D vector quantities

13. Which of the following shows thecorrect conversion of units?

A 24 mm3 =2.4 x 10-6 m3

B 300 mm3=3.0 x 10-7 m3

C 800 mm3=8.0 x 10-2 m3

D 1 000 mm3=1.0 x 10-4 m3

14. Which of the following measurements

is the shortest ?

A 3.45 x 103 m

B 3.45 x 104 cm

C 3.45 x 107

mmD 3.45 x 1012m

15. The Hitz FM channel broadcasts radio

waves at a frequency of 92.8 MHz in

the north region. What is the frequency

of the radio wave in Hz?

A 9.28 x 104 B 9.28 x 105

C 9.28 x 107 D 9.28 x 1010

16. An object moves along a straight line

for time, t. The length of the line, s is

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given by the equation2

2

1gts = . The

SI unit of g is

A m2 s2 B m s-2

C s-1 D s-2 m

Part B : Structure Question

1. A car moves with an average speed of 75 km h-1 from town P to town Q in 2 hours as

shown in Figure 1. By using this information, you may calculate the distance between thetwo towns.

P Q

Figure 1

(a) (i) Based on the statements given, state two basic quantities and their respective

SI units.

(ii) State a derived quantity and its SI unit.

(b) Convert the value 1 . m to standard form.

5 x 10-3

(c) Complete Table 1 by writing the value of each given prefix.

Table 1

(d) Power is defined as the rate of change of work done. Derive the unit for power in

terms of its basic units.

(e) Calculate the volume of a wooden block with dimension of 7 cm, 5 cm breadth and 12

cm height in m3 and convert its value in standard form.

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2. Figure 2 shows an ammeter of 03 A range.

Figure 2

(a) (i) Name component X. ...

(ii) What is the function of X? .

(b) Table 2 shows three current readings obtained by three students.

Table 2

(i) Did all the students use the ammeter in Figure2? ...

(ii) Explain your answer in (b)(i).

3. Figure 3 shows the meniscus of water in a measuring cylinder K, L, and M are three eyepositions while measuring the volume of the water.

(a) (i) Which of the eye positions is

correct while

taking the reading of the volume

of water?

.

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Figure 3

(b) The water in the measuring cylinder is

replaced with 30 cm3 of mercury.

(i) In Figure 4, draw the meniscus of the

mercury in the measuring cylinder. Figure 4(ii) Explain why the shape of the meniscus of mercury is as drawn in (b)(i).

2272180-chapter-1-introduction-to-physics

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