A class presentat

1. Grade 9 Physics
?

2. Introduction Surveys
● Some people have already done them, but they
may have changed. So please do a new one
- thank you.
● Mind Map / Brainstorm:
What is Physics?
Is it useful, and if so why?
What do you know about it?
What would you like to learn?
● Sculpture: Use half a packet of clay to make
something which symbolises Physics.

3. PHYSICS
● Physics is the study of the laws of the
universe.
● Other Sciences often apply the laws of
Physics, but to think of them this way is
often pointless.
● Physics came out of Astronomy, which is the
oldest academic discipline.
● This year we will cover mechanics (how and
why things move), waves, light (including
sight) and heat (including climate change).
http://en.wikipedia.org/wiki/File:CollageFisica.jpg

4. Housekeeping
● Welcome to the first year of MYP Grade 9
Science!
● Textbooks
- none as yet. We will use the same textbooks
as Grade 9s last year, and may issue them
further into the course.
● Any questions?

5. Sculptures
● Show and Tell :)

6. Mathematics
● “The Book of
Nature is
Written in the
Language of
Mathematics.”
-Galileo Galilei (image from Wikipedia)

7. Scientific Notation
Scientists often use scientific notation / standard
form.
How comfortable are you with this.
Example Problems
1. Write ten million in scientific notation.
12
2. Write 4.3 * 10 as an ordinary number.
3. What is 4*1012 / 2*109?

8. Metric Prefixes
106 phones = 1 megaphone
10-6 phones = 1 microphone
2000 mockingbirds = 2 kill a
mockingbird
10 cards = 1 decacards
10-6 fish = 1 microfiche

9. More Metric Conversions
10-2 mental
1012 bulls
10-12 boos
10 millipedes
106 aches

10. le Système international d'unités
(SI Units)
Units used to be problematic, with every country or group
having their own, often inconsistent.
The Metric system was developed in France after the
revolution, and was officially adopted in France in
1779.
SI Units became the official worldwide units in a
conference “General Conference on Weights and
Measures” in 1971.
There are three countries which haven’t adopted them:
Burma (Myanmar), Liberia and the USA.

11. Quantities and Units
● A quantity is something which can
be measured. For example:
_______________
___________________________
________.
● Quantities are measured in units.
Most (all?) quantities have
multiple units for the same thing,
and this can be problematic.
● The Mars Climate Orbiter crashed
because the Europeans and
Americans used different units in
its programming. http://upload.wikimedia.org/wikipedia/co
Mars_Climate_Orbiter_2.jpg

12. Distance
The (average) radius of the Earth is
6371km.
Calculate the Earth’s quadrant (1/4 of
the circumference).
This is not coincidence.
Officially, it used to be one ten-
millionth of the distance from
the Equator to the north pole
through Paris.
Nowadays it is defined in terms of the
speed of light.

13. Time
Calculate the time period of a pendulum
whose length is one metre, using the
formula where g = 9.8.

14. Mass
A kilogram is officially
defined as the
mass of a piece of
platinum-iridium
alloy at the Bureau
international des
poids et mesures, in
Sevres, France.
http://upload.wikimedia.org/wikipedia/commons/thumb/b/b5/CGKilogram.jpg/800px-CGKilogram.jpg

15. Derived Quantities
● Most quantities other than mass, length and
time are derived from these quantities. For
example:
●
●
●

16. Density of a Microscope Slide
● Calculate the density of a microscope slide, in
kg / m3.
mass
density=
volume

17. Bookwork
● Questions on page 11, 13 and 16.

18. Precision and Accuracy
● Precision is how small the units on a measuring device
are. For example, an electronic balance (scales) can
measure to 0.001g, whereas kitchen scales may only
measure to the nearest gram. So electronic balances
are more precise.
● Accuracy is how correctly something can take a
measurement.
● Bathroom scales may measure to 0.1g (precision) but
may not do so accurately. If one scale reads a 60kg
object as 59.1g, they have a precision of 0.1g and an
accuracy of 1.
● It's important to know how accurate a measurement in
Physics is.

19. Assessment
● A (Knowledge and Understanding)
1. Arriving Safely test (before October Break)
2. Light and Sight test (when?)
● B, C (Experiment)
Do heavier objects fall faster than lighter objects? Investigation and
Explanation.
● D - ROTIOS (formerly “One world”)
1. The safety of helmets:
- are they effective?
- are they worthwhile?
- are standards high enough?
- should they be compulsory?
It may be presented as an essay, presentation or movie. It should be
persuasive.
OR: The Shinkansen: history, how it works, safety, popularity, environmental
issues (environmental issues and benefits over aeroplanes), and possible
future developments including the new maglev train from Tokyo – Osaka. You
could also discuss whether or not it is likely that trains will replace aeroplanes
for long-distance travel; the Seikan tunnel.
●

20. Motion
● Motion means movement.
● In this unit we will look at speed, acceleration
and forces.

21. Speed (review from Grade 8)
● Speed measures how fast distance
something's position changes with time. Speed = time
Quantity SI Unit Other units
(symbol) (symbol) (symbols)
Distance (d) metres Kilometres (km)
miles
Time (t)
Speed (v)
second
metres per
Minutes, hours
(hr), days
Kilometres per
d
second hour (km/hr)
÷ ÷
● Example: Melanie runs 100m
in twelve seconds. How fast v X
x
t
does she run in m/s?
● How long will it take her to run to Yokohama station (5 km)?

22. Problems
1. A. Kosuke is walking home. If he walks 100m in 40s, what is
his average speed?
B. How long will it take him to walk to Motomachi station if it
is 500m away?
2. Aska is riding to Kamakura, 25km away. If he rides at an
average speed of 6m/s, how long will it take him to get there?
●

23. Converting m/s to km/hr
● How do we convert m/s to km/hr and vice versa?
m/s ×60×60
m/hr ÷1000
km/hr
OR ×3600
m/s ×3600
km/hr
1. Convert a driving speed of 100km/h to m/s.
2. Convert a sprint speed of 10m/s to km/h.

24. Acceleration
● Acceleration is a change in speed.
● Speeding up, slowing down and changing
direction are all acceleration.
●
Units are m/s2. Why?
● Calculate the acceleration v
2 of a car which takes
in m/s
ten seconds to accelerate
÷ ÷
from rest to 100km/h.
a X
x
t

25. Acceleration Problems
1)Calculate the acceleration of a sprinter who
takes two seconds to reach a speed of 10 m/s.
2) An object falling under gravity (assuming
friction is negligible – more on this in the first
assignment) accelerates at a speed of 10 m/s 2.
How long will a falling object take to travel at
100km/hr.
3)How fast will a falling object be traveling after
20 seconds?

26. Acceleration
● Calculate the acceleration of an object which
takes 8 seconds to reach a speed of 24m/s.
● How long will it take to reach the speed of
sound, of around 340m/s?

27. The Human Body
● Is the human body a speedometer, or an
accelerometer?
Images of speedometer and accelerometer
unnecessary.
http://www.vernier.com/images/cache/product.acc-bta._physics._hero._001.590.332.jpg
http://img.dxcdn.com/productimages/sku_2682_1.jpg

28. The Aeroplane
Images of aeroplanes were to show
that we feel acceleration as a plane
takes off and when it decelerates
immediately after landing, but we don't
'feel' the speed as a plane cruises at
the same speed.
http://worldairlinenews.files.wordpress.com/2009/09/jal-japan-airlines-777-300-ja742j-02tko-pae-
ndlr.jpg http://vintage.johnnyjet.com/images/PicForNewsletterJapan2005JAL747InAir.jpg
http://www.boeing.com/news/releases/2006/photorelease/q4/061116c_lg.jpg

29. Force Diagrams
● An unbalanced force is required for an object to
accelerate.

30. Falling Objects
● It used to believed that
heavy objects fall
faster than light Animated GIF
objects. Galileo is the of Galileo not
first person in necessary.
recorded, western
history to actually test
this.
● Conclusion: They fell
at (about) the same
speed.
http://physics-animations.com/Physics/anipisa.gif

31. Galileo's Philosophy
● Galileo believed that
theories should be simple
and harmonise each other.
His theory of falling objects
simplified theories of motion.
● He also believed that
experiments were necessary
to test theories, but it didn't
matter if the results weren't
perfect.
http://upload.wikimedia.org/wikipedia/commons/thumb/d/d4/Justus_Sustermans_-_Portrait_of_Galileo_Galilei,_1636.j
Justus_Sustermans_-_Portrait_of_Galileo_Galilei,_1636.jpg

32. Ptolemy Verses Copernicus
● Ptolemy was a Greek
Astronomer who devised a
system of the Solar Please load the
System which we now images below.
know is wrong, but which
could predict the location
of the planets more http://www.conservapedia.com/images/thumb/0/0e/Co
accurately than
Copernicus's system
could.
● Galileo said this didn't http://www.ps-19.org/Crea00Intro-Ps19/Astronomy_file
matter, because the
Copernican system was
simpler and harmonised
his theory about Jupiter
and its moons he had
discovered. Did it matter?

33. Copernicus Verses Ptolemy
http://www.conservapedia.com/images/thumb/0/0e/Copernicus_system.gif/300px-Copernic
http://www.ps-19.org/Crea00Intro-Ps19/Astronomy_files/PtolemyEpicycles.jpg
Copernicus was wrong because the planets move in Ellipses,
which was later determined by the genius (arguably one of
astronomy's greatest scientists) Johannes Kepler.

34. The Hammer and the Feather
http://www.youtube.com/watch?v=5C5_dO

35. What about on Earth?
● If two objects of the same dimensions, surface
and surface area, but different mass, are
dropped, will they reach the ground at the same
time? Plan and carry out an investigation to find
out.
● Your experiment should include a prediction,
procedure, results and processing (?) and a
conclusion which answers your prediction and
discusses your results using a Grade 9 (or
beyond) understanding of forces.

36. Inertia
● Inertia is the property of
matter which makes it resist Image of
change in its motion a man
(acceleration). pulling a
train by
● Objects with greater mass attaching
have greater inertia. Inertia is s wire to
a property of all matter, and his teeth.
since it increases with mass
we use mass to calculate
acceleration in calculations.
http://1.bp.blogspot.com/-4G-w9-k42F
● Inertia can be imagined by
having to whirl something
around in space.

37. Force and Acceleration
● An unbalanced force causes something to accelerate.
● Newton's second law:
Force = mass * acceleration
The force is the net (combined) force of all forces acting on
the object.
● Example 1: A. Calculate the acceleration of a 5kg object if
a force of 40N force pushes it but a friction force of 5N
opposes it.
B. How long will it take the object to reach a speed of 35
m/s?
● Example 2: Calculate the force required to make an 800kg
car accelerate from 0 to 100km/h in one minute.
Hint: first convert everything to SI units. Second calculate
the acceleration. Third calculate the force.

38. At the lights
● Why does a motorbike accelerate faster than a
car, even though it has a smaller engine (which
can provide less force)?
Picture of motorcycles and a car
taking off at an intersection in
Vietnam removed and unecessary.
http://howwasyourtrip.files.wordpress.com/2010/01/dsc_2881.jpg

39. Falling Under Gravity
● The Weight force due to gravity is:
Weight = mass * gravity
2
where g is acceleration due to gravity = 10m/s .
(formula from MS Science)
● Complete the table to show acceleration of
different objects under gravity.
Mass (kg) Weight Acceleration
(mass * gravity) (force/mass)
1kg
5kg
10kg
100kg

40. Quick Questions
● Please answer these in your
books.
1. Explain the difference and
relationships between
-mass and weight
-mass and inertia http://physics-animations
2. Explain why, in Galileo's
famous experiment, the two
rocks fell at the same speed,
even though the one with
greater mass had a stronger
weight force pulling it down to
Earth.

41. Friction and Drag
● Drag is a type of friction which acts on an object
moving through a fluid (eg the atmosphere).
● What factors might affect the drag force on
something?
● Answer: surface, surface area, speed
Images of a baseball and a parachutist falling
through the sky removed.

42. The Falling Ping Pong Balls
● Let's oversimplify our ping pong balls to give them nice round numbers. We
will assume they have just been dropped, so their speeds are similar,
therefore the friction is similar.
● For each, calculate: it's weight, its net force and its acceleration.
● Extension exercise:
1. Sketch a graph of speed verses time and calculate how long each should
take to reach the ground.
2. Two objects, of mass M and m, are dropped. Both experience the same
friction force F. Calculate the acceleration of each in terms of M, m, g and F.
Drag = 1N Drag = 1N
1kg 200g
Weight = ______N
Weight = ______N

43. Why did Galileo's Experiment Seem to Work?
● For dense objects like rocks, the friction force is
much smaller than the gravitational force.
● Heavier objects are generally larger (assuming
the same ________), therefore they are also
subjected to greater friction force.

44. Terminal Velocity
● As a falling object's speed increases, the friction
force increases but the weight force stays the
same.
● Eventually these two forces cancel each other
out, so the speed stays the same.
● Skydivers reach a terminal velocity of 190km/h
(belly first) or 300km/h (head first).
● A falling coin can be very dangerous because its
surface area is very small and it is very dense, so
its terminal velocity is huge.
Image of a skydiver removed.

45. Blog Time!
● Explain the experiment we did, what we
observed and why.
● Did you prove Galileo wrong? Would he care?
Explain your answer in as much detail as
possible.

46. Terminal Velocity Investigation
● Investigate a factor which affects terminal
velocity.

47. TEST
● When do you 'want' the test (preferably
sometime next week).
?

48. Vectors and Scalars
● A scalar is a quantity with a magnitude (size) but no
direction.
Eg __________________________________
● A vector is a quantity for which magnitude and direction
are important.
Eg __________________________________
● Vectors can have a negative value. For example, if a
10N force upwards is 10N, then the same force
downwards must be written (as a vector) as -10N.
● When using vectors, it is important to decide which
direction is positive and negative (eg North = positive,
south = negative OR up = positive, down = negative

49. Speed and Velocity
● Speed is a scalar. It does not take into account
direction. A speedometer reads speed.
● Velocity is a vector. Its direction is important.
Eg if a car is travelling north and has a velocity
of 27m/s, what is the velocity of a car it passes
at the same speed travelling south?

50. Displacement and Distance
● Distance measures how far
something has travelled. An
odometer measures distance.
● Displacement measures how far
something is from its starting point.
A GPS unit measures
displacement.
http://fs01.androidpit.info/trss/x94/392294.png
http://upload.wikimedia.org/wikipedia/commons/thumb/7/7d/Odometer2.jpg/120px-Odometer2.jpg

51. Motion Graphs
● A stone is thrown upwards at 10m/s (ignore
drag). Gravity causes it to accelerate
downwards at 10m/s2. Eventually it falls back
down and lands at the same spot.
a) How long will it take to come to a momentary
stop.
b) How long will it take to fall back down.
c) Sketch distance-time, displacement time,
speed-time and velocity-time graphs for its
entire path.

52. Speed (m/s) Velocity (m/s)
10 10
1 2 Time (s) 1 2 Time (s)
-10

53. Distance (m) Displacement (m)
10 10
5 5
1 2 Time (s) 1 2

54. Newton's Second Law
Force = Mass * Acceleration
Newton's Third Law
Every force has an equal and opposite force.

55. Collisions
● Collisions are important in Physics and
(unfortunately) in real life for some professions,
eg road safety, and (fortunately) particle physics.
● A 1000kg car travelling at 100 km/hr crosses the
centre-line and collides with a 10 000kg truck
moving at 30km/hr in the opposite direction. After
the collision, both move together. What is the
final speed and direction of the combined
wreckage?
● What would we need to know to solve this
problem, and how could we work it out?

56. A new quantity
Momentum, p, measures 'quantity of motion'.
Heavy objects and fast-moving objects have
greater momentum.
Momentum = mass * veocity.
p=mv
1. What are its base units?
2. Calculate the momentum of a 1200kg car
moving at 50km/hr.

57. Momentum is a Vector
Momentum = mass * velocity
p=mv
Use units to show that momentum is the product
of force and time required to push something
there.
Eg Aska is riding his bike (combined mass
rounded up to 100kg) and accelerates from rest to
10m/s in five seconds.
a) calculate his acceleration
b) calculate the force he provides
c) calculate the product of force and time.
d) calculate his momentum using p=mv.

58. Conservation of Momentum
In collisions, total momentum is always the same.
In Physics terms, we say momentum is
conserved.
Eg a 500 gram trolley is moving at 2 m/s, when a
100 gram block is dropped onto it. Calculate the
new velocity of the trolley.

59. The Original Problem
A 1000kg car travelling at 100 km/hr north
crosses the centre-line and collides with a 10
000kg truck moving at 30km/hr south. After the
collision, both move together. What is the final
speed and direction of the wreckages?
ANS: 18km/h south.

60. Car and a Train
A 1000kg car stops on a railway line, and a 5000
kg train traveling at 60km/h North collides with it.
After the collision, both the car and the train stick
together. Calculate the velocity of the train and the
car after the collision.
ANS: 16.340m/s North

61. Momentum and Time
● For something to change momentum quickly, it
must have a large force exerted on it. This force
can be fatal in collision.
p
 F=
t
Eg. A car is travelling at 20m/s when it crashes
into a tree. It takes a 50kg person in it 0.2s to
stop when they hit the windscreen. Calculate
the average force on the person.

62. It's All About the Time
● Time is critical in determining the force on something which
changes momentum suddenly.
● What can be done to increase the time it takes something to
stop?
p
 F=
t
http://www.carlsbadchiropractic.com/airbag.jpg

63. Safety
● Explain how airbags reduce harm during
accidents.
● Explain how helmets reduce harm during
accidents.
● Outline three reasons for and against helmets
being compulsory.
Formative assessment: How do you want to
present it?

64. Extension: The pool table
(2 Dimensions)
What's the
danger?
What can
we do
about it?