chapter introduction to physics teacher guide
TRANSCRIPT
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SMK Gombak Setia Physics Module Form 4Teachers Guide Chapter 1 : Introduction To Physics_________________________________________________________________________________________
CHAPTER 1 : INTRODUCTION TO PHYSICS
1.1 Understanding Physics
1
Mechanical Energy
PHYSICS
Study of the natural phenomena and the
ro erties of matter.
Solid
Liquid
Gas
Mechanical Energy
Heat Energy
Light Energy
Wave Energy
Electrical Energy
Nuclear Energy
Chemical Energy
Relationship
with
matter
Properties of
Ener
Relationship
with
energy
Properties of
Matter
formsstates
Matter Energy
Mechanics
Propertieso matter
Heat
Light
Wave
in the fields of
Electricity &Electromagnetism
Atomic Physics& Nuclear
Electronics
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SMK Gombak Setia Physics Module Form 4Teachers Guide Chapter 1 : Introduction To Physics_________________________________________________________________________________________
1.2 PHYSICAL QUANTITIES
Base quantity
1 A physical quantity is ..
2 Examples of scientific instruments :
3 A base quantity is a physical quantity which cannot be defined in terms of other physical
quantities.
4 Study the following picture and list the physical quantities that can be measured.
5 List of 5 basic physical quantities and their units.
Base quantity Symbol S.I. Unit Symbol for S.I. Unit
Length
Mass
Time
CurrentTemperature
6 Two quantities that have also identified as basic quantity. There are :
i) ..unit .. ii) . unit ..
Standard Form
The list of physical quantities :
1. .
2. .
3. .
4. .
5. .
6. .
7. .
8. .
batteryattery
any quantity that can be measured by a scientific instrument.
stopwatch, metre rule balance,thermometer,ammeter
etc.
Height,
mass,
size,
age,
temperature,
current
Power,
Thermal energy
l meter m
m kilogram kg
t second s
I Amppere A
T Kelvin K
Light intensity candela Amount of substance mol
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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 :
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
10110-1
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
simplify the expression of very large and small numbers
6.37 x 106m
9.11 x 10-31 kg
3.0 x 10-4 m
7.2 x 10-8 m
5.5 x 10-7
represent a large physical quantity or extremely small quantity in S.Iunits.before the unit as a multiplying factor.
1 x 1012 m
3.6 x 10-3A
1.33 MA = 1.33 x 106A
= 1.33 x 10 6-(-9) nA
= 1.33 x 10 -15 nA
1.23 Tm to unit m unit
1.23 Tm = 1.23 x 10 12m
= 1.23 x 10 12 (-6)m
= 1.23 x 10 18m
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
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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 =
Derived quantities
1 A derived quantity is .
2 Determine the derived unit for the following derived quantities.
Derived
quantityFormula 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
densityvolume
massensityd = 3
3mkg
m
kg =
velocity time
ntdisplaceme
elocityv =1
sms
m =
momentum momentum = mass x velocity kg m s-1
Accelerationtime
velocityinchangeonaccelerati =
2
11-1
sm
ssms
sm
=
=
Force force = mass x acceleration kg m s-2 Newton (N)
pressure
area
forcepressure=
weight weight = mass x gravitational acceleration
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)
kgm s-2 / m2 kg m-1 s-2 (Nm-2)
kg ms -2 Newton (N)
N m Joule (J)
J s -1 Watt (W)
Kg ms-2 Joule (J)
9.1 x 10 1MHz
12.8 Mm = 1.28 x 10 1 Mm
383 Mm = 3.83 x 10 2 Mm
6.0 x 10 12 Tm
a physical quantity which combines several basic quantities through
multiplication, division or both
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SMK Gombak Setia Physics Module Form 4Teachers Guide Chapter 1 : Introduction To Physics_________________________________________________________________________________________
Derived
quantityFormula Derived unit
Name of
derived unit
charge charge = current x time Ampere second(As)
Coulomb (C)
voltagecharge
workvoltage = J C-1 Volt (v)
resistancecurrent
voltageresistance= v A-1 Ohm ()
Note that the physical quantities such as width, thickness, height, distance, displacement,
perimeter, radius and diameter are equivalent to length.
1.3 SCALAR AND VECTOR QUANTITIES
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 Direction1. 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
1.4 MEASUREMENTS
Using Appropriate Instruments to Measure
1 There are various types of.
2 We must know how to choose the appropriate instrument to ..
3 Examples of instrument and its measuring ability.
Measuring instrument Range of measurement Smallest scale division
Measuring tape
Quantity which has only magnitude or size
Mass, Length, Speed, volume
Quantity which has magnitude or size and direction.
Velocity, Force, Displacement, Acceleration
measuring instrument with different measuring capabilities.
measure a particular quantity.
Up to a few meters 0.1 cm
1 m 0.1 cm (0.01 m)
10 cm 0.01 cm
less than 2 cm (20 mm) 0.001 cm (0.01 mm)
is use to measure electric current5
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Meter rule
Vernier caliper
Micrometer screw gauge
4 Sample of measuring instruments :
4.1 Ammeter : ..
4.2 Measuring cylinder : ....................
4.3 Ruler :
wrong right wrong
10 11 12 13 14 15 Reading = cm
4.4 Vernier calliper
A venier calliper is used to measure :a. b. .
c. d. .
A vernier calliper gives readings to an accuracy of .... cm.
pointer mirrorpointer mirror
Pointers image is behind the pointer
incorret 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
cm 0 1 2 3 4SKALA
UTAMA0
5 10
inside jawsVernier scale
outside jaws
Main scale
is use to determine the volume of liquid.
is use to determine the length
small object depth of a hole
external diameter of a cylinder or pipe internal diameter of a pipe or tube
0.1 cm
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Length of vernier scale = cm
Vernier scale is divided into 10 divisions
Length of the divisions = . cm
The diagram below shows a vernier calliper with reading.
Vernier calliper reading = . cm
4.5 Micrometer screw gauge.
A micrometer screw gauge is used to measure :
a.
b. .
c.
Example :
0 5 10
0 1
0 1
0 5 10
Main scale in cm
Vernier scale
0 1 2 3 4 5 6 7 8 9 10
0 1 cm
Main scale = .
Vernier scale = ..
Final reading = ..
Find the division ofvernier scale which iscoincides with any part ofthe main scale
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 : ..
Sleeve scale :
Thimble scale : .
Total reading : ...
The differenct between the main scale and vernier scaleis = . cm
0.15
objects that are small in sizediameter of a wire
diameter of small spheres such as ball bearings
0.5 50
0.01 mm 4.5 mm0.01 mm 0.22 mm
4.62 mm
0.9
0.09
0.01 cm
0.2 cm
0.06 cm
0.26 cm
2.0 mm
0.22 mm
2.22 mm
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4.6 Some others measuring instruments :
..
. ..
Hands-on activity 1.1 on page 1 of the practical book to learn more about choosing
appropriate instruments.
Exercise: Vernier Callipers And Micrometer Screw Gauge
1. Write down the readings shown by the following
(a)
(b)
(c)
(d)
0 5 10
0 1
0 510
6 7
0 5 10
7 8
0 5 10
4 5A B
QP
Answer: 7.79 cm..
Answer: 4.27 cm..
Answer: 6.28 cm..
Answer: 0.02 cm..
Analogue stopwatch digital stopwatch thermometer miliammeter
Measuring tape measuring cylinder beaker
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2. (a) The following diagram shows the scale of a vernier calliper when the jaws are closed.
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.
3. Write down the readings shown by the following micrometer screw gauges.
(a) (b)
Answer: . Answer:..
(c) (d)
Answer: Answer:.
0 5 10
5 6
0 5 10
0 1
Reading shown = 5.64.cm
Corrected reading = 5.62..cm
35
400 5
3
0
0 5 10
3
5
20
250
15
200 5
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4. (a) Determine the readings of the following micrometer screw gauges.
Zero error = 0.02.. mm Zero error = 0.03.. mm
(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: 6.88 mm Answer: ..12.32 mm(c) (d)
Answer:4.71 mm Answer: 9.17 mm
6. (a) Determine the readings of the following micrometer screw gauges.
Zero error = -0.02 mm Zero error = 0.03.. mm
0 0
45
5
0
0
5
0
0 0 5
15
20
Zero error = 0.03mm Reading shown = 6.67..mm
Corrected reading = 6.64..mm
35
400 5
3
0
0 5 10
3
5
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.
Accuracy and consistency in measurements.
1. Accuracy :
2. Consistency :
3. Sensitivity :
..
.. ..
Hands-on activity 1.2 on page 2 of the practical book to determine the sensitivity of
some measuring instruments.
Errors in measurements
1. All measurements are values
2. In other word, it is a matter of
3. This is because
4. Two main types of errors:
4.1
target
target
The ability of an instrument to measure nearest to the actual value
The ability of an instrument to measure consistently with little or no relativedeviation among readings.The ability of an instrument to detect a small change in the quantity measured.
consistent but inaccurate consistent and accurate inaccurate and not consistent
Accuratebut not consistent inaccurate but consistent inaccurate but not consistent
5
0
0 0 5
15
20
Zero error = 0.03.mmReading shown = .6.67..mm
Corrected reading = 6.64..mm
of approximation only.
how close the measurement is to the actual value.
error exist in all measurements.
Systematic errors
a weakness of the instrument
the difference between reaction time of the brain and the action.
zero error is when the pointer is not at zero when not in use.
Range of the measuring instrument absolute error .
Reaction time of the brain.
Initial reading is not at the zero scale zero error
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where the pointer is not at zero when not in use
+0.03 cm- 0.04 cm
+ 0.02 mm - 0.03 mm
SMK Gombak Setia Physics Module Form 4Teachers Guide Chapter 1 : Introduction To Physics_________________________________________________________________________________________
Occurs due to :
a)
b)
c)
Examples :
a)
b)
c)
Absolute error :
.
.
Example :
Parallax error :
Zero error : ...
Correct reading = observed reading zero error
Refer to the smallest reading that can be measured by an instrument.
If, the smallest reading = 0.1 cm
Then, Absolute error = 0.1 / 2 = 0.05 cm
It occurs because the position of the eye is not perpendicular to the scale of theinstrument.
wrong
right position of the eye (no error)wrong
Zero error =
0 1 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 =
0 1 cm
Horizontalreference
Horizontalreference3 divisions above
horizontal reference2 divisions below
horizontal reference
Positive zero error Negative zero error
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4.2
Occurs due to
a)
b)
c)
Example :a) ..
b) ..
.....................................................................................................................
1.5 SCIENCETIFIC INVESTIGATION
Steps Explanation
1
Making
observation
2Drawing
inferences
A conclusion from an observation or phenomena using informationthat already exist.
3 Identifying andcontrolling
variables
Variables are factors or physical quantities which change in thecourse of a scientific investigation.There are three variables :
i. Manipulated variables physical quantity which change according to the aim of the
experiment.ii. Responding variables physicals
quantity which is the result of the changed by manipulatedvariable.
iii. Fixed variables physicals quantitieswhich are kept constant during the experiment.
4Formulating a
hypothesis
Zero error of screw meter gauge
Zero error = Zero error = -
Random error
carelessness in making the measurement.
parallex error , incorrect positioning of the eye when taking the readings.
sudden change of ambient factors such as temperature or air circulation.
Readings are close to the actual value but they are not consistent.
Can be minimized by consistently repeating the measurement at different places in
an identical manner.
Gather all available information about the object or phenomenon to be
studied.Using the five senses, sight, hearing, touch, taste and smell.
Statement of relationship between the manipulated variable and theresponding variable those we would expect.
Hypothesis can either be true or false.
i. Conduct an experiment includes the compilation andinterpretation of data.
ii. Making a conclusion regarding the validity of the hypothesis.
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5Conducting
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 Example : refer to the situation above
1 InferenceThe period ofthe oscillation depends on the length of the pendulum.
2 Hypothesis When the length of the pendulum increases, the period of theoscillation increases.
3 Aim Investigate the relationship between length and period of a simple
pendulum.4 Variables Manipulated variable : the length of the pendulum.
Responding variable : PeriodFixed variable : the mass of the pendulum and the displacement.
5 List of
apparatus and
materials
Retort stand with clamp, 100 cm of thread, bob,meter rule, 2 blocks of clamp wood, protractor and
stopwatch.
6 Arrangement of
the apparatus
l
Retort standprotractor
l
bob
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7 Procedures
8 Tabulate the
data
9
10
11
Analyse the
data
Discussion
Conclusion
T / s
1.4
1.2
1.0
0.8
0.6
0.4
0.2
Graf of period, T vspendulums
length, l
1. Set up the apparatus as shown in the figure above.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 = t10oscillations10
5. Repeat steps 2, 3 and 4 using l = 50.0 cm, 40.0 cm, 30.0 cm and20.0 cm
1.581.58
1.501.50
1.311.31
1.191.19
0.990.99
15.815.8
15.015.0
13.113.1
11.911.9
9.99.9
15.715.7
15.015.0
13.113.1
11.911.9
9.99.9
15.815.8
15.015.0
13.113.1
11.911.9
9.99.9
60.060.0
50.050.0
40.040.0
30.030.0
20.020.0
Period/ sPeriod/ s
(T = t(T = t1010/10)/10)AverageAverage
2211
Length,Length,ll //cmcm
Time for 10 oscillations / s
10 20 30 40 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.
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Reinforcement Chapter 1
Part A :Objective Question
1. Which of the following is a base SIquantity?
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 basic
unit?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 tand another physical quantity kisrelated by the equation v - u = kt.The unit forkisA m s-1 B m-1 s C
m s-2 D m2 s-2
7. Which of the following has the smallestmagnitude?
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 measurements
is 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 250m.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 the
correct conversion of units?
A 24 mm3 =2.4 x 10-6 m3
B 300 mm
3
=3.0 x 10
-7
m
3
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 mm
D 3.45 x 1012m
15. The Hitz FM channel broadcasts radiowaves 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
given by the equation2
2
1gts = . The SI
unit of g isA m2 s2 B m s-2
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C s-1 D s-2 m
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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.
(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.
Distance : m and time : s
Speed m s-1
= 0.2 x 103 m= 2.0 x 102m
10-9
10-6
106
109
Power =time
work=
time
ntdisplacemeForceUnit =
s
mkgms 2= kg m2s-3
Volume = (7 x 10-2) (5 x 10-2) (12 x 10-2)= 420 x 10-6
= 4.20 x 10-4 m3
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SMK Gombak Setia Physics Module Form 4Teachers Guide Chapter 1 : Introduction To Physics_________________________________________________________________________________________