Date post: | 27-Apr-2015 |
Category: |
Documents |
Upload: | kamalharmoza |
View: | 4,618 times |
Download: | 2 times |
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
1
CHAPTER 1 : INTRODUCTION TO PHYSICS
1.1 Understanding Physics
Mechanical Energy
PHYSICS
Study of the natural phenomena and the
properties of matter.
Solid
Liquid
Gas
Mechanical Energy
Heat Energy
Light Energy
Wave Energy
Electrical Energy
Nuclear Energy
Chemical Energy
Relationship
with
matter
Properties of
Energy
Relationship
with
energy
Properties of
Matter
forms states
Matter Energy
Mechanics
Properties
of matter
Heat
Light
Wave
in the fields
of
Electricity &
Electromagnetism Atomic Physics
& Nuclear
Physics
Electronics
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
2
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
Current
Temperature
6 Two quantities that have also identified as basic quantity. There are :
i) …………………………..unit …………..
ii) ………………………. unit ……………..
The list of physical quantities :
1. ……………………………………….
2. ……………………………………….
3. ……………………………………….
4. ……………………………………….
5. ……………………………………….
6. ……………………………………….
7. ……………………………………….
8. ……………………………………….
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 Ampere A
T Kelvin K
Light intensity candela
Amount of substance mol
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
3
Standard Form
1 Standard form = A x 10n , 1 ≤ A < 10 and n = integer no.
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 = 0.000000000000000000000000000000 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
10
9
10
6
10
3
10
0
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
simplify the expression of very large and small numbers
6.37 x 106 m
1.673 x 10-27
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.I
units.
before the unit as a multiplying factor.
1 x 1012
m
3.6 x 10-3
A
1.33 MA = 1.33 x 106 A
= 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 12
m
= 1.23 x 10 12 – (-6)
m
= 1.23 x 10 18
m
5456 pA to MA unit
5456 pA = 5.456 x 10 3 + (-12)
pA
= 5.456 x 10 -9
pA
= 5.456 x 10 -9 –(6)
MA
= 5.456 x 10 -15
MA
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
4
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
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 volume
massensityd
3
3mkg
m
kg –
velocity time
ntdisplaceme elocityv 1sm
s
m –
momentum momentum = mass x velocity kg m s-1
–
Acceleration time
velocityinchangeonaccelerati
2
11-1
sm
ssms
sm
–
Force force = mass x acceleration kg m s-2
Newton (N)
pressure area
force pressure
weight weight = mass x gravitational acceleration
work work = force x displacement
power time
workpower
kinetic energy 2velocitymassK.E
2
1
kg m 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 101
MHz
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
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
5
Derived
quantity Formula Derived unit
Name of
derived unit
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)
voltage charge
workvoltage J C
-1 Volt (v)
resistance current
voltageresistance v A
-1 Ohm (Ω)
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 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
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 ……………………………..
Quantity which has only magnitude or size
Mass, Length, Speed, volume
Quantity which has magnitude or size and direction.
Velocity, Force, Displacement, Acceleration
Ý
Ý Ý
Ý
Ý Ý
measuring instrument with different measuring capabilities.
measure a particular quantity.
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
6
3 Examples of instrument and its measuring ability.
Measuring instrument Range of measurement Smallest scale division
Measuring tape
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 mirror pointer mirror
Pointer’s image is behind the pointer
incorret reading correct
reading
1 2 3 0 4
1 2 3 0 4
Pointer’s 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
is use to determine the volume of liquid.
is use to determine the length
2.5 cm
small object depth of a hole
external diameter of a cylinder or pipe internal diameter of a pipe or tube
0.01cm
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 current
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
7
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. ………………………………………………
0 5 10
0 1
0 1
0 5 10
Main scale in cm
Vernier scale
cm 0 1 2 3 4 SKALA
UTAMA 0
5 10
inside jaws Vernier scale
outside jaws
Main scale
0 1 2 3 4 5 6 7 8 9 10
0 1 cm
Main scale = ………………….
Vernier scale = …………………..
Final reading = …………………..
Find the division of vernier scale which is coincides with any part of the main scale
Anvil spindle sleeve (main scale) thimble (circular scale) ratchet frame
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 : …………..
The differenct between the main scale and vernier
scale is = ……………………………. cm
0.15
objects that are small in size
diameter of a wire
diameter of small spheres such as ball bearings
0.5 ÷ 50
0.01 mm 4.5 mm
0.01 mm 0.22 mm
4.62 mm
1.0
0.01
0.01 cm
0.2 cm
0.06 cm
0.26 cm
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
8
Example :
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)
Sleeve scale : ……………
Thimble scale : ………….
Total reading : …………...
0 5 10
7 8
0 5 10
4 5 A B
Q P
Answer: …7.89 cm…………..
Answer: …4.27 cm…………..
2.0 mm
0.22 mm
2.22 mm
Analogue stopwatch digital stopwatch thermometer miliammeter
Measuring tape measuring cylinder beaker
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
9
(c)
(d)
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: ………6.87 cm……… Answer:……12.32 cm…………..
0 5 10
0 1
0 5 1
0
6 7
0 5 10
5 6
0 5 10
0 1
Answer: ……6.28 cm………..
Answer: …0.02 cm…………..
Reading shown = …5.64…….cm
Corrected reading = …5.62……..cm
35
40 0 5
30
0 5 10 35
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
10
(c) (d)
Answer:………4.71 cm………………… Answer:……9.17 cm………
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…………
20
25 0
0 0
45
5
0
0
5
0
0 0 5
15
20
15
20 0 5
Zero error = +0.03………mm Reading shown = 6.67………..mm
Corrected reading = 6.64………..mm
35
40 0 5
30
0 5 10 35
20
25 0
15
20 0 5
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
11
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 ……………………………………………
Occurs due to :
a) ………………………………………………………………………………………
b) ………………………………………………………………………………………
c) ………………………………………………………………………………………
Examples :
a) ………………………………………………………………………………………
b) ………………………………………………………………………………………
c) ………………………………………………………………………………………
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 relative
deviation 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
Accurate but not consistent inaccurate but consistent inaccurate but not consistent
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
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
12
Absolute error :
……………………………………………………………………………………….…………
………………………………………………………………………………………………….
Zero error : …………………………………………………………………………………...
Correct reading = observed reading – zero error
4.2 ……………………………………………..
Occurs due to
a) ………………………………………………………………………………………
b) ………………………………………………………………………………………
c) ………………………………………………………………………………………
Example :
a) 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.
Parallax error :
Example :
Zero error of screw meter gauge
Positive zero error
Horizontal
reference
Horizontal
reference 3 divisions above
horizontal reference 2 divisions below
horizontal reference
Zero error = - 0.02 mm
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
where the pointer is not at zero when not in used
+0.03 cm - 0.04 cm
Positive zero error Negative 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.
It occurs because the position of the eye is not perpendicular to the scale of the instrument
wrong
right position of the eye (no error)
wrong
Positive zero error
Zero error = +0.03
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
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
13
1.5 SCIENCETIFIC INVESTIGATION
Steps Explanation
1 Making
observation
Gather all available information about the object or phenomenon
to 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
Identifying
and controlling
variables
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.
ii. Responding variables
- physical quantity which is the result of the changed
by manipulated variable.
iii. Fixed variables
physical quantities which are kept constant during the experiment.
4 Formulating a
hypothesis
Statement of relationship between the manipulated variable and
the responding variable those we would expect.
Hypothesis can either be true or false.
5 Conducting
experiments
i. Conduct an experiment includes the compilation and
interpretation of data.
ii. Making a conclusion regarding the validity of the hypothesis.
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
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.
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
14
4 Variables
Manipulated variable : the length of the pendulum.
Responding variable : Period
Fixed 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
stop watch.
6 Arrangement of
the apparatus
7 Procedures
8 Tabulate the
data
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 = 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
11..5588
11..5500
11..3311
11..1199
00..9999
1155..88
1155..00
1133..11
1111..99 99..99
1155..77
1155..00
1133..11
1111..99 99..99
1155..88
1155..00
1133..11
1111..99 99..99
6600..00
5500..00
4400..00
3300..00
2200..00
PPeerriioodd// ss
((TT == tt1100//1100)) AAvveerraaggee 22 11 LLeennggtthh,,ll //
ccmm
Time for 10 oscillations / s
Retort stand protractor
l
bob
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
15
9
10
11
Analyse the
data
Discussion
Conclusion
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 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
T / s 1.4
1.2 1.0 0.8 0.6 0.4 0.2
Graf of period, T vs pendulum’s length, l
0 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.
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
16
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 10
9 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
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 the
correct conversion of units?
A 24 mm3 =2.4 x 10
-6 m
3
B 300 mm3=3.0 x 10
-7 m
3
C 800 mm3=8.0 x 10
-2 m
3
D 1 000 mm3=1.0 x 10
-4 m
3
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
m
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 10
5
C 9.28 x 107 D 9.28 x 10
10
16. An object moves along a straight line
for time, t. The length of the line, s is
given by the equation 2
2
1gts . The
SI unit of g is
A m2 s
2 B m s
-2
C s-1
D s-2
m
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
17
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 102 m
10
-9
10-6
106
109
Power =time
work =
time
ntdisplacemeForce Unit =
s
mkgms 2
= kg m2 s
-3
Volume = (7 x 10
-2) (5 x 10
-2) (12 x 10
-2)
= 420 x 10-6
= 4.20 x 10
-4 m
3
Physics Module Form 4
Teacher’s Guide Chapter 1 : Introduction To Physics
_________________________________________________________________________________________
18
2. Figure 2 shows an ammeter of 0—3 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 eye
positions 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?
…….……………………………………
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).
……………………………………………
No
3rd
readings obtained by student 2 and 3 are out of the meter range.
L
The cohesive force is larger than the adhesive force
Mirror
To avoid parallax error