EDUHF1017 Physical Phenomena - L1
EDUF 1017
Science Foundations 2
Introduction
Physical Phenomena
8 lectures in Chemistry LT2
4 workshops in Education lab U431
Reference book:
EDUF 1017 Science Foundations 2 Physical Phenomena
available from the Copy Centre for $8.00
(go to www.usyd.edu.au/su/ups/notes/notes_login.html and look up code no. R508759)
Lecturer: John O’Byrne
School of Physics Room 568
9351 - 3184
[email protected]
www.physics.usyd.edu.au/ugrad/jphys/jphys_webct/EDUF1017.html
1
EDUF 1017 Physical Phenomena L1
EDUF 1017 Physical Phenomena L1
Assessment
Assessment
Assignment - Outline
- Assignment
Final exam - lecture material
Final exam - workshop material
3%
12%
15%
15%
EDUF 1017 Physical Phenomena L1
Due Dates:
Outline
3
3.
4.
5.
6.
7.
8.
EDUF 1017 Physical Phenomena L1
4
Units
Introduction - Distance, Speed, Acceleration
Newton’s First Law, Force, Gravity
Newton’s Second & Third Law, Walking & Running
Density, Buoyancy, Archimedes Principle
Jumping, Kinetic & Gravitational Potential Energy
Waves, Sound, Hearing
Charge, Current, Voltage, Batteries
Resistance, Power, Electrical Networks & Safety
EDUF 1017 Physical Phenomena L1
Assignment
11:00am Thursday 15 September
(in the lecture)
5:00pm Monday 17 October
(to ……..)
Choose from the given situation and
Analyse the physics
Design 2 activities to teach the physics concepts to primary children.
~2 pages for each section plus diagrams
Work in teams of 2 if you wish
Further details on separate sheet
Outline
2.
2
Assignment
1.
Web site - copies of notes and other information:
5
What are the units of the measurements?
We use the SI (Système International) units - mks system based mostly on
Length - metre (m)
Mass - kilogram (kg)
Time - second (s)
Electric Current - ampere (A)
Temperature - kelvin (K)
There are also the cgs units, imperial units and ‘US
customary’ units
EDUF 1017 Physical Phenomena L1
6
1
EDUHF1017 Physical Phenomena - L1
Prefixes:
Each unit is based on a
standard - e.g. the metre was
defined as one ten millionth
of the distance from the
equator to the pole through
Paris.
1012
tera
T
109
giga-
G
106
mega-
M
103
kilo-
k
10-1
deci-
d
10-2
centi-
c
10-3
milli-
m
10-6
micro- µ
10-9
nano-
n
10-12 pico-
p
EDUF 1017 Physical Phenomena L1
Example
Speed
7
Speed is a scalar and is always positive.
Average velocity is the displacement divided by the time
it took. Velocity may be positive or negative.
SI Units are length/time - e.g. m/s or ms-1
EDUF 1017 Physical Phenomena L1
8
Converting between units
(Hecht Example 2.4)
A 600km cross-country car rally is won by a team of two
drivers each of whom had the wheel for half the distance
of the trip. If one averaged 60 km/h and the other 20
km/h, what was their overall average speed?
How fast do they go?
Human walking
Human running
Car
Aircraft
Sound
Light
EDUF 1017 Physical Phenomena L1
“The distance travelled in a given amount of time”
Defined bit more carefully:
Average speed is the distance travelled (along any path)
divided by the time it took
9
Constant Speed
30 m/s
Example of conversion
EDUF 1017 Physical Phenomena L1
10
Distance-time graph
Constant or uniform speed - equal distances in equal times
EDUF 1017 Physical Phenomena L1
110 km/hr
11
EDUF 1017 Physical Phenomena L1
If speed (“rate-of-change of
distance”) is constant, the
distance-time graph is a
straight line
Slope of the line is the ratio
of the rise to the run
= a distance divided by a
time
= speed
12
2
EDUHF1017 Physical Phenomena - L1
Instantaneous speed
Lines with different
slopes on a distancetime graph correspond
to different speeds
Greater slope means
faster moving
EDUF 1017 Physical Phenomena L1
13
How to specify the speed at an instant?
Narrow the time (t) of the average - geometrically this
comes closer and closer to the tangent to the curve
The slope of the tangent at P is the instantaneous speed
EDUF 1017 Physical Phenomena L1
14
Acceleration
How do we quantify changes in motion? - speed up
(accelerate), slow down (decelerate), changes in direction.
Acceleration is the time rate of change of velocity.
EDUF 1017 Physical Phenomena L1
15
Units are (m/s)/s - m/s2 or ms-2 - “metres per second squared”
Acceleration may be positive or negative
When vf < vi, , a < 0, the runner has decelerated.
When vf > vi, , a > 0, the runner has accelerated.
EDUF 1017 Physical Phenomena L1
16
Slope of velocity-time graphs
The slope of the tangent to the
velocity-time graph at a point is
the instantaneous acceleration
A straight-line velocity-time
graph indicates uniform
acceleration
Uniform acceleration happens
when equal changes in velocity
occur in equal intervals of time.
EDUF 1017 Physical Phenomena L1
17
3