Introduction To Physics Teacher Guide 2009

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

CHAPTER 1 : INTRODUCTION TO PHYSICS

Mechanical Energy

1.1 Understanding Physics PHYSICS Mechanical Energy

Study of the natural phenomena and the properties of matter. Matter

Solid

Light Energy

Energy

states

Liquid

Heat Energy

Wave Energy

forms

Electrical Energy

Gas

Nuclear Energy Chemical Energy

Properties of Matter

Relationship with matter

Relationship with energy

Properties of Energy

in the fields of

Mechanics

Properties of matter

Wave

Heat

Electronics

Electricity & Electromagnetism

Light

1

Atomic Physics & Nuclear

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

1.2

PHYSICAL QUANTITIES

Base quantity

any quantity that can be measured by a scientific instrument. A physical quantity is …………………………………………………………………….. Stopwatch, metre rule balance, thermometer, ammeter Examples of scientific instruments:……………………………………………………… etc. A base quantity is a physical quantity which cannot be defined in terms of other physical

1 2 3

quantities. 4

Study the following picture and list the physical quantities that can be measured. The list of physical quantities : Height, 1. ………………………………………. mass, 2. ………………………………………. size, 3. ………………………………………. age, 4. ………………………………………. temperature, 5. ………………………………………. current 6. ………………………………………. Power, 7. ………………………………………. Thermal energy 8. ………………………………………. Pressure 9. ………………………………………. battery

5

List of 5 basic physical quantities and their units. Base quantity

Symbol

S.I. Unit

Length

l

meter

Mass Time

m

kilogram

kg

t

second

s

I

Ampere

A

T

Kelvin

K

Current Temperature

Symbol for S.I. Unit m

6. Two quantities that have also identified as basic quantity. There are: i) …………………………..unit ………….. ii) ………………………. unit ………… Light intensity candela Amount of substance mol

…..

2

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

Standard Form 1

the large and small numbers Standard form = A x 10nsimplify , 1 <expression A < 10 andofnvery = integer

2

Standard form is used to …………………………………………………………………...

3

Some physical quantities have extremely small magnitudes. Write the following quantities in standard form :

6.37 x 106 m -31

9.11 x 10 kg a. Radius of the earth = 6 370 000 m =…………………………………………………. -5

10 000 m 000 000 000 000 911 kg =………... b. Mass of an electron = 0.000 000 0003.0 000x 000 -8

7.2 x 10 m c. Size of a particle = 0.000 03 m = ……………………………………………………… -7

5.5 x 10 m b. Diameter of an atom = 0.000 000 072 m = …………………………………………... c. Wavelength of light = 0.000 000 55 m = …………………………………………….. represent a large physical quantity or extremely small quantity in S.I units. before the unit as a multiplying factor. 1. Prefixes are usually used to ………………………………………………………………... Prefixes

2. It will be written …………………………………………………………………………… Eg :

3. The list of prefixes :

1 × 1012 m 1 Tm = ……………………………………. 3.6 × 10-3A

Tera (T)

12

10

109

Giga (G)

106

Mega (M)

103

kilo (k)

102 1 10 0

10

-1

10

-2

10-310

mili (m)

10-6

micro (µ)

10-9

nano (n)

10-12

pico (p)

3.6 mA = ……………………………………. How to change the unit ; Eg : 1.33 MA = 1.33 × 106 A Hekto (ha) 1. Mega to nano Deka (da) desi (d) centi (c)

= 1.33 × 10 6-(-9) nA = 1.33 × 10 -15 nA 1.23 Tm to unit µm unit 2. Tera to micro 1.23 Tm = 1.23 x 10 12m = 1.23 x 10 12 – (-6)m = 1.23 x 10 18m 3. piko to Mega 5456 pA to MA unit 5456 pA = 5.456 x 10 3 + (-12) pA = 5.456 x 10 -9pA = 5.456 x 10 -9 –(6) MA = 5.456 x 10 -15 MA

3

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

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: 9.1 × 10 1MHz a. Frequency of radio wave = 91 000 000 Hz = …………………………………………. 12.8 Mm = 1.28 × 10 1 Mm b. Diameter of the earth = 12 800 000 m = ……………………………………………… 383 Mm = 3.83 × 10 2 Mm c. Distance between the moon and the earth = 383 000 000 m = ……………………… 6.0 × 10 15 Tg d. Mass of the earth = 6 000 000 000 000 000 000 000 000 kg = ……………………… Derived quantities 1 2

a physical quantity which combines several basic quantities through A derived quantity is …….………………………………………………………………… multiplication, division or both ……………………………………………………………………………………………… Determine the derived unit for the following derived quantities. Derived quantity

Formula

Derived unit

Name of derived unit

Area

area = length x width

m x m = m2

–

Volume

volume = length x width x height

m x m x m = m3

–

Density Velocity

Acceleration

density = velocity =

acceleration =

mass volume

kg m3

displacement time change in velocity time

= kg m −3

–

m = m s −1 s

–

m s −1 = m s -1 s −1 s = m s −2

–

momentum

momentum = mass x velocity

kg m s-1

–

Force

force = mass x acceleration

kg m s-2

Newton (N)

kgms −2 m2

kg m-1 s-2 (Nm-2) @ Pa

pressure

pressure =

force area

Weight

weight = mass x gravitational acceleration

kg ms -2

Work

work = force x displacement

Nm

Power

power =

work time

J s -1

4

Newton (N)

Joule (J)

Watt (W)

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

Derived quantity

Formula

Derived unit

Name of derived unit

kinetic energy

1 K.E = × mass × velocity 2 2

kg m2s-2

Joule (J)

potential energy

P.E = mass x gravitational acceleration x height

kg m2s-2

Joule (J)

charge

charge = current x time work charge

voltage

voltage =

resistance

resistance =

voltage current

Ampere second (As)

Coulomb (C)

J C-1

Volt (V)

VA-1

Ohm (Ω)

Quantity which has only magnitude or size Note that the physical quantities such as width, thickness, height, distance, displacement, Length, are Speed, volumeto length. perimeter, radiusMass, and diameter equivalent Quantity which has magnitude or size and direction. 1.3 SCALAR AND VECTOR QUANTITIES Velocity, Force, Displacement, Acceleration 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 1. The temperature in the room is 25 0C 2. The location of Ayer Hitam is 60 km to the northwest 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

1.4

MEASUREMENTS

5

√ Direction √ √

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

Using Appropriate Instruments to Measure measuring instrument with different measuring capabilities. is used to determine the volume of liquid. 1 There are various types of…………………………………………………………………. 2

measure a particular quantity. We must know how to choose the appropriate instrument to ……………………………..

3

Examples of instrument and its measuring ability. Range of measurement Measuring instrument Measuring tape Up to a few meters Meter rule 1m Vernier caliper is used to determine the length 10 cm Micrometer screw gauge

4

less than 2 cm (20 mm) Sample of measuring instruments:

Smallest scale division

0.1 cm 0.1 cm (0.01 m) 0.01 cm 0.001 cm (0.01 mm)

4.1 Ammeter : …………………………………………………………………………….. incorrect reading correct 1 2 3 1 2 is3used to measure electric current 0 4 reading 0 4 mirror

pointer

pointer

mirror

Pointer’s image is behind the pointer

Pointer’s image can be seen

4.2 Measuring cylinder : ……………………………………………………....................

water

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

4.3 Ruler : ……………………………………………………………………………………… wrong 10

11

12

right 13

wrong 14

15

Reading = ……………… cm

4.4 Vernier calliper A venier calliper is used to measure:

small object

depth of a hole

external diameter of a cylinder or pipe

internal diameter of a pipe or tube

a. ………………………………………………b. ………………………………………….

0.1 cm 6

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

c. ………………………………………………d. …………………………………………. A vernier calliper gives readings to an accuracy of …………………………………...…. cm.

inside jaws scale1 cmVernier 0

2

3

4 Main scale SKALA

0

outside jaws Main scale in cm

0.9

Length of vernier scale = ……… cm

0

1

Vernier scale is divided into 10 divisions 0

0.09

Length of the divisions = ………. cm

10

5

The different between the main scale and vernier 0.01 cm scale is = ……………………………. cm

0

Main scale

1

0.2 cm

0

= ………………….

Vernier scale

1 2 3 4 5

cm

6 7 8 9 10

Find the division of vernier scale which is coincides with any part of the main scale

0.06 cm

Vernier scale = …………………..

0.26 cm

Final reading = …………………..

Example: The diagram below shows a vernier calliper with reading. 0

1

objects that are small in size diameter of a wire diameter of small spheres such as 0

5

10

0.15 ball bearings Vernier calliper reading = ……………. cm

0.5 ÷ 50 0.01 mm

4.50 mm

4.5 Micrometer screw 0.01 mmgauge.

0.12 mm

A micrometer screw gauge is used to measure : a. ………………………………………………

7

4.62 mm

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

b. …………………………………………. c. ……………………………………………… One complete turn of the thimble (50 division) moves the spindle by 0.50 mm. Division of thimble = ………………….. = ………………….. A accuracy of micrometer screw gauge = ……………..

Sleeve scale : …………… Thimble scale : …………. Total reading : …………..

Example : 2.00 mm Sleeve scale : …………… 0.22 mm Thimble scale : …………. 2.22 mm Total reading : …………... 4.6 Some others measuring instruments :

Analogue stopwatch digital stopwatch ……………………… ……………………

Measuring tape ……………………….

thermometer Ammeter ……………………… ………..

measuring cylinder ……………………..

beaker ………………

Hands-on activity 1.1 on page 1 of the practical book to learn more about choosing appropriate instruments. Exercise: Vernier Callipers 1. Write down the readings shown by the following (a) 7 8

0

8

5

10

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

Answer: …7.89 cm…………..

4

(b)

A

B

P 0

(c)

5

Answer: …4.27 cm…………..

Q 10

5

6

7

Answer: ……6.28 cm……….. 0

(d)

1

5

0

Answer: …0.02 cm…………..

1

0

10

5

2. (a) The following diagram shows the scale of a vernier calliper when the jaws are closed. 1

0

0

10

5

Zero error = …+ 0.02……… cm (b).

The following diagram shows the scale of the same vernier calliper when there are 40 pieces of cardboard between the jaws. 5

Reading shown

6

=0 …5.64…….cm 5

10

Corrected reading = …5.64 - (+ 0.02)= 5.62……..cm

9

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________ 3. Diagram 3 (a) shows the reading on a pair of vernier callipers when its jaws are closed

with nothing in between them. Diagram 3(b) shows the reading when it is used to measure the thickness of a piece of wood. 1

0 cm

0

5

4

2

5

0

10 (a)

5

6

10

(b)

What is the actual thickness of the wood? Zero error

-0.05 = ………………….. cm

Reading shown

4.51 = …………………..cm

4.51- (-0.05) =4.56 Actual thickness of the wood = ……………………………….cm Exercise: Micrometer Screw Gauge 1. (a) Determine the readings of the following micrometer screw gauges. 0

0

5

0 45

0

Zero error = …-0.02…….. mm

Zero error = …+0.03…….. mm

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

0

0

5

20

5

0

15

Zero error = +0.03………mm

Reading shown

= 6.67………..mm

Corrected reading = 6.67-(+0.03)=6.64 mm

2. Write down the readings shown by the following micrometer screw gauges. (a) (b) 0

5

40

0

10

5

10

3 5 3 0

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

35

Answer: …6.88 mm………… (c)

Answer: …..12.32 mm…… (d)

0

25

0

5

20

20 15

Answer:………4.71 mm…………

Answer:

9.17 mm…………

Accuracy and consistency in measurements. The ability of an instrument to measure nearest to the actual value 1. Accuracy : ………………………………………………………………………………… The ability of an instrument to measure consistently with little or no relative 2. Consistency :deviation ……………………………………………………………………………… among readings. The ability of an instrument to detect a small change in the quantity measured. 3. Sensitivity : …………………………………………………………………………………

inaccurate but consistent …………………………

consistent and accurate ……………………………..

of approximation only. how close the measurement is to the actual value. error exist in all measurements. Systematic errors Accurate but not consistent ……………………..

inaccurate and not consistent ………………………………

Hands-on activity 1.2 on page 2 of the practical book to determine the sensitivity of a weakness of the instrument some measuring instruments. the difference between reaction time of the brain and the action. Errors in measurements zero error is when……………………………………………………………… the pointer is not at zero when not in use. 1. All measurements are values 2. In other word, it is a matter of …………………………………………………………… Range of the measuring instrument 11– absolute error . Reaction time of the brain.

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

3. This is because …………………………………………………………………………… 4. Two main types of errors: 4.1 …………………………………………… Occurs due to : a) ……………………………………………………………………………………… b) ……………………………………………………………………………………… c) ………………………………………………………………………………………

Refer to the smallest reading that can be measured by an instrument. Examples :

a) ……………………………………………………………………………………… b) ……………………………………………………………………………………… c) ………………………………………………………………………………………

If, the smallest reading = 0.1 cm Absolute error : ……………………………………………………………………………… Then, Absolute error = 0.1 / 2 = 0.05 cm ……….………………………………………………………………………………………… It occurs because the position of the eye is not perpendicular to the scale of the …………………. instrument. Parallax error : ……………………………………………………………………………… wrong Example :

position of the eye (no error) wrong

where the pointer is not at zero when not in use Zero error : …………………………………………………………………………………... Correct reading = observed reading – zero error Zero error Posit of Vernier calliper Positive zero error 0

Negative zero error 1

0

cm

+0.03 cm

1

cm

- 0.04 cm

0 1 2 3 4 5 6 7 8 9 10

0 1 2 3 4 5 6 7 8 9 10

Zero error =

Zero error =

Zero error of screw meter gauge Negative zero error

Positive zero error

12

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

Horizontal reference Horizontal reference 2 divisions below horizontal reference Zero error = + 0.02 mm

3 divisions above horizontal reference

Zero error = - 0.03 mm

Random error 4.2 …………………………………………….. Occurs due to carelessness in making the measurement. a) ……………………………………………………………………………………… parallex error , incorrect positioning of the eye when taking the readings. b) ……………………………………………………………………………………… sudden change of ambient factors such as temperature or air circulation. c) ……………………………………………………………………………………… Example : Readings are close to the actual value but they are not consistent. a) …………………………………………………………………………………..… Can be minimized by consistently repeating the measurement at different places in b) …………………………………………………………………………………….. an identical manner. ..................................................................................................................... 1.5

SCIENCETIFIC INVESTIGATION Steps

Explanation

1

Making observation

Gather all available information about the object or phenomenon be studied. Using the five senses, sight, hearing, touch, taste and smell.

2

Drawing inferences

A conclusion from an observation or phenomena using information that already exist.

3

Variables are factors or physical quantities which change in the course of a scientific investigation. There are three variables : i. Manipulated variables – physical quantity which change according to the aim of the experiment. Identifying ii. Responding variables – physicals quantity which is the result of and controlling the changed by manipulated variable. variables iii. Fixed variables – physicals quantities which are kept constantduring the experiment. Statement of relationship between the manipulated variable and the responding variable those we would expect. Hypothesis can either be true or false but in correct direction.

4

to

Formulating a hypothesis i. Conduct an experiment includes the compilation and interpretation of data. ii. Making a conclusion regarding the validity of the hypothesis. 13

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

5

Conducting experiments

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 1

Inference

2

Hypothesis

3

Aim

4

Variables

5

List of apparatus and materials

6

Example : refer to the situation above The period of the oscillation depends on the length of the pendulum. When the length of the pendulum increases, the period of the oscillation increases. Investigate the relationship between length and period of a simple pendulum. Manipulated variable : the length of the pendulum. Responding variable : Period Fixed variable : the mass of the pendulum and the displacement. Retort stand with clamp, 100 cm of thread, bob,

Arrangement of the apparatus

Retort stand

protractor

ll

bob

14

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________ 1. Set up the apparatus as shown in the figure above. 7 Procedures 2. Measure the length of the pendulum,l = 60.0 cm by using a meter rule. 3. Give the pendulum bob a small displacement 300.Time of 10 oscillations is measured by using a stop watch. 4. Repeat the timing for another 10 oscillations. Calculate the average time. Period = t10 oscillations 10 5. Repeat steps 2, 3 and 4 using l = 50.0 cm, 40.0 cm, 30.0 cm and 20.0 cm

8

Tabulate the data

Length,l Length,l / cm

Time for 10 oscillations / s 2 1 Average 15.8 15.7 15.8 15.0 15.0 15.0 13.1 13.1 13.1 11.9 11.9 11.9 9.9 9.9 9.9

60.0 50.0 40.0 30.0 20.0

9

Analyse the data

T/s

Period/ s (T = t10/10) 1.58 1.50 1.31 1.19 0.99

Graf of period, T vs pendulum’s length, l

1.4 1.2 1.0 0.8 0.6 0.4 0.2 0

10

20

30

1 0

40

Discussion

Conclusion 11

50

60 l / cm

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.

15

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

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

10. The diameter of a particle is 250 µm. 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

2. Which of the following is a derived quantity? A Length B Mass C Temperature D Voltage

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

3. Which of the following is not a basic unit? A Newton B kilogram C ampere D second

12. Velocity, density, force and energy are A basic quantities B scalar quantities C derived quantities D vector quantities

4. Which of the following quantities cannot be derived? A Electric current B Power C Momentum D Force

13. Which of the following shows the correct 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

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

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 mm D 3.45 x 1012 µm

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

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

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

16. An object moves along a straight line for time, t. The length of the line, s is 1 2 given by the equation s = gt . The 2 SI unit of g is A m2 s2 B m s-2 -1 C s D s-2 m

9. Which of the following measurements is the longest? A 1.2 x 10-5 cm B 120 x 10-4 dm C 0.12 mm D 1.2 x 10-11 km

16

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

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 the two towns. P Q

Figure 1 (a) (i) Based on the statements given, state two basic quantities and their respective SI units. Distance : m and time : s ……………………………………………………………………………………… (ii) State a derived quantity and its SI unit. Speed – m s-1 ……………………………………………………………………………………… (b) Convert the value = 0.2 x 103 m = 2.0 x 102 m

1 . m to standard form. 5 x 10-3

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

10-9 10-6 106 109

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. work Force × displacement kgms −2 × m Power = = Unit = = kg m2 s-3 time time s (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. Volume = (7 x 10-2) (5 x 10-2) (12 x 10-2) = 420 x 10-6 = 4.20 x 10-4 m3

17

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

2. Figure 2 shows an ammeter of 0—3 A range.

Figure 2 Mirror (a) (i) Name component X. ………………………………………………………………... To avoid parallax error (ii) What is the function of X? …………………………………………………………. (b) Table 2 shows three current readings obtained by three students.

Table 2 No (i) Did all the students use the ammeter in Figure2? ..…………………………………. (ii) Explain your answer in (b)(i). 3rd readings obtained by student 2 and 3 are out of the meter range. ……………………………………………………………………………………… 3. Figure 3 shows the meniscus of water in a measuring cylinder K, L, and M are three eye positions while measuring the volume of the water. (a) (i) Which of the eye positions is correct while L taking the reading of the volume of water? …….…………………………… ………

Figure 3 (b) The water in the measuring cylinder is replaced with 30 cm3 of mercury. (i) In The cohesive force is Figure drawthe theadhesive meniscus of the larger4,than force mercury in the measuring cylinder. Figure 4 (ii) Explain why the shape of the meniscus of mercury is as drawn in (b)(i). 18

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

………………………………………………………………………………………

19