These are the slides of physics chapter measurements.

1. Measurement

2. Presentation
 Usually, we use “magnitude +unit” to
present a measurement of a quantity.
 Mass A=1.04 kg

3. Units and quantities
 SI Basic unit
mol
Mole
Amount of
substance
K
Kelvin
Temperature
A
Ampere
Electric current
s
Second
Time
kg
Kilogram
Mass
m
Meter
Length
Symbol
Unit name
Basic quantity

4. Units and quantities
 Derived units
 area、volume、Force、weight、frequency
 Density、speed、work done、power、
pressure
 Potential difference/voltage、resistance

5. How to deal with very large or
very small number?
Use a shorthand way by counting the
number of zeros.
1000000=106
0.000001=10-6

6. Prefixes
Prefixes can be added to SI base and derived units
to make larger or smaller units.
Multiplying Factor Prefix Abbreviation
10-1
10-2
10-3
10-6
10-9
10-12
deci d
centi c
milli m
micro μ
nano n
pico p

7. Prefixes
101 deca da
102 hecto h
103 kilo k
106 mega M
109 giga G
1012 tera T
Multiplying Factor Prefix Abbreviation

8. Conversion of units
Question :
Convert:
a) 30kmh-1 to ms-1
b)0.01m2 to mm2
c) 400nm to μm
d)120 000 min-1 to s-1

9. Common Apparatusequipment
 Meter rule
 Tape rule
 Vernier caliper
 Micro-screw gaugeMicrometer
Length Measurement

10. Human error
Example 1
Professor Messer
is trying to
measure the length
of a piece of wood:
Discuss what he is doing wrong.
How many mistakes
can you find?

11. Human error
1. Measuring from 100 end
2. 95.4 is the wrong number
3. ‘mm’ is wrong unit (cm)
4. Hand-held object, wobbling
5. Gap between object & the rule
6. End of object not at the end of the rule
7. Eye is not at the end of the object (parallax)
8. He is on wrong side of the rule to see scale.
Answers:
How many did you find?

12. Length Measurement
 Make sure the reading starts from “0” or get
the reading from the difference of two ends.
(avoid zero error)
 Your eye must be right over the mark on the
scale. (avoid parallax error)
 Precision: the quality of being very exact or
correct

13. How to measure the thickness of a
piece of paper in a book accurately?
 Measure the thickness of 100-pages and find
out the average
 Try to measure the thickness in different part
of the pages.
 Use more precise apparatus

14. How to measure the diameter of a
small metal wire accurately?
 Wrap the wire 30 turns around a pencil
tightly, with one after another,
 Measure the length of these 30 turns on the
pencil, find out the average
 Try to measure the thickness in different
part of the wire.
 Use more precise apparatus

15. How to measure the diameter of a
metal cylinder accurately?
 Set-square/wooden blocks and ruler
 Vernier caliper

16. Volume Measurement
2 For solid
 regular shape----sphere/cube
 Irregular shape——put the small object into
the measuring cylinder, immerge the object
in the water, the difference between the
initial reading and final reading is the
volume of the solid.
Any other methods?

17. Volume Measurement
 use measuring cylinder/burette
 The vessels must be upright and your eye
must be level with the bottom of the curved
liquid surface/meniscus.
1 For Liquid

18. To measure mass
 With beam balance
 Top-pan balance

19. •Electric top-pan balance
2.push tare button to
zero the balance.
1.Check if the balance is turned
on. If not, press the on/off
button and wait until the display
reads 0.0 g.
How to measure the mass of the powder by using
electrical balance?

20. 
Place a container or large, creased weighing
paper on the balance pan. Push tare button
to zero the balance.

21. To measure force
 with spring
balance
 Newton meter
 force meter

22. Measure time/period
 Stop watch
 Reaction time
 Record some
times of
readings and
take the
average as
period.

23. How to measure a short time
accurately?
Electric
timer

24. Assignment
How to measure the density of an
irregular object? Please write
down in detail.

25. How to measure the density of
a metal wire accurately? Please
write down in detail including
your data and calculation.
Assignment

27. 18-Dec-23
reading vernier scales

28. 18-Dec-23
applet

29.  Vernier caliper

31. Micrometer screw gauge

32.  3.24mm
20
25
0
( 1 ) ( 2 )
5
25
30
7.5+28×0.01
Answer=7.78mm
=7.79mm

33. operation
18/12/2023

34. 18/12/2023
reading the scale

35. 18/12/2023
self test

37. 20
25
0
( 1 ) ( 2 )
5
25
30