Physics 101
Lecture 1
Units
Assist. Prof. Dr. Ali ÖVGÜN
EMU Physics Department
www.aovgun.com
January 22-25, 2013
January 22-25, 2013
Class Code will be given
in class
January 22-25, 2013
Course Information:
Instructor
❑ Instructor: Ali Övgün
❑ Office: AS 246 ( Arts and Sciences Faculty)
❑ Office hour: To be announced (check my
webpage). Other time by appointment
❑ Email: ali.ovgun@emu.edu.tr
❑ Website: www.aovgun.com
Course Information:
❑ Midterm Exam 1 (30%)
❑ Midterm Exam 2 (15%)
❑ Lab Experiments(5%)
❑ Lab Exam (10%)
❑ Final Exam (40%)
❑ Participation to laboratory:
❑ Note that students who do not attend at least
three lab sessions will automatically get NG.
❑ Thenet attendance rate from the
whole academic activities
(theoretical lectures, applications,
labs, quizzes and all exams) should
be minimum 50% in order to not to
get NG.
January 22-25, 2013
COURSE SCHEDULE
❑ 1st Week Chapter 1 – Units
❑ 2nd Week Chapter 3 – Vectors
❑ 3rd Week Chapter 2 – Motion Along Straight Line
❑ 4th Week Chapter 4 – Motion in 2D and 3D
❑ 5th Week Chapter 5,6 – Force and Motion
❑ Midterm 1
❑ 6th Week Chapter 7 – Kinetic Energy and Work
❑ 7th Week Chapter 8 – Conservation of Energy
❑ 8th Week Chapter 9 – Linear Momentum
❑ Midterm 2
❑ 9th Week Chapter 10– Rotation
❑ 10th Week Chapter 11– Torque,Angular Momentum
❑ 11th Week Chapter 12 – Equilibrium
❑ 12th Week Chapter 13 - Gravitation
❑ 13th Week Review
❑ 14th Week Finals
Physics and Mechanics
❑ Physics deals with the nature and properties of matter
and energy. Common language is mathematics.
Physics is based on experimental observations and
quantitative measurements.
❑ The study of physics can be divided into six main areas:
◼ Classical mechanics – Physics I (Phys. 101)
◼ Electromagnetism – Physics II (Phys. 102)
◼ Optics –
◼ Relativity –
◼ Thermodynamics –Physics II (Phys. 102
◼ Quantum mechanics –
◼ Classical mechanics deals with the motion and
equilibrium of material bodies and the action of
forces. January 22-25, 2013
Classical Mechanics
❑ Classical mechanics deals with the motion of objects
❑ Classical Mechanics: Theory that predicts qualitatively &
quantitatively the results of experiments for objects that
are NOT
◼ Too small: atoms and subatomic particles – Quantum
Mechanics
◼ Too fast: objects close to the speed of light – Special Relativity
◼ Too dense: black holes, the early Universe – General Relativity
❑ Classical mechanics concerns the motion of objects that
are large relative to atoms and move at speeds much
slower than the speed of light (i.e. nearly everything!)
January 22-25, 2013
Introduction
❑ Physics 101 – Course Information
❑ Brief Introduction to Physics
❑ Chapter 1 – Measurements (sect. 1-6)
◼ Measuring things
◼ Three basic units: Length, Mass, Time
◼ SI units
◼ Unit conversion
◼ Dimension
January 22-25, 2013
Chapter 1 Measurement
❑ To be quantitative in Physics requires measurements
❑ How tall is Ming Yao? How about
his weight?
◼ Height: 2.29 m (7 ft 6 in)
◼ Weight: 141 kg (310 lb)
❑ Number + Unit
◼ “thickness is 10.” has no physical meaning
◼ Both numbers and units necessary for
any meaningful physical quantities
January 22-25, 2013
Type Quantities
❑ Many things can be measured: distance, speed,
energy, time, force ……
❑ These are related to one another: speed =
distance / time
❑ Choose three basic quantities (DIMENSIONS):
◼ LENGTH
◼ MASS
◼ TIME
❑ Define other units in terms of these.
January 22-25, 2013
SI Unit for 3 Basic
Quantities
❑ Many possible choices for units of Length,
Mass, Time (e.g. Yao is 2.29 m or 7 ft 6 in)
❑ In 1960, standards bodies control and define
Système Internationale (SI) unit as,
◼ LENGTH: Meter
◼ MASS: Kilogram
◼ TIME: Second
January 22-25, 2013
Fundamental Quantities and SI Units
Length meter m
Mass kilogram kg
Time second s
Electric Current ampere A
Thermodynamic Temperature kelvin K
Luminous Intensity candela cd
Amount of Substance mole mol
January 22-25, 2013
Why should we care about
units?
❑ Mars Climate Orbiter:
http://mars.jpl.nasa.gov/msp98/orbiter
❑ SEPTEMBER 23, 1999: Mars Climate Orbiter Believed To
Be Lost
❑ SEPTEMBER 24, 1999: Search For Orbiter Abandoned
❑ SEPTEMBER 30, 1999:Likely Cause Of Orbiter Loss Found
The peer review preliminary findings indicate that one team used
English units (e.g., inches, feet and pounds) while the other used
metric units for a key spacecraft operation.
January 22-25, 2013
The Quick 6: Six Unit
Conversion Disasters
1. Can you imagine losing
❑ Think
you had a $125 million thanks to a little
metric system error? That’s
bad day at work? exactly what happened in
1999 when NASA lost a Mars
orbiter because one team
used metric units for a
❑ Forgetting to calculation and the other
team didn’t.
convert units can 2. In 1983, an Air Canada plane ran out of
fuel in the middle of a flight. The cause?
result in big-time Not one but two mistakes in figuring how
disasters like these
much fuel was needed. It was Air Canada’s
first plane to use metric measurements
six examples. and clearly not everyone had the hang of
it yet. Luckily, no one was killed and only
two people received minor injuries. That’s
amazing considering the flight crew
thought they had double the fuel they
actually had.
SI Length Unit: Meter
❑ French Revolution Definition,
1792
❑ 1 Meter = XY/10,000,000
❑ 1 Meter = about 3.28 ft
❑ 1 km = 1000 m, 1 cm = 1/100
m, 1 mm = 1/1000 m
❑ Current Definition of 1 Meter:
the distance traveled by light in
vacuum during a time of
1/299,792,458 second.
January 22-25, 2013
SI Time Unit: Second
❑ 1 Second is defined in terms of an “atomic clock”– time
taken for 9,192,631,770 oscillations of the light emitted
by a 133Cs atom.
❑ Defining units precisely is a science (important, for
example, for GPS):
◼ This clock will neither gain nor lose a second in 20 million years.
January 22-25, 2013
SI Mass Unit: Kilogram
❑ 1 Kilogram – the mass of a
specific platinum-iridium alloy kept at
International Bureau of Weights and
Measures near Paris. (Seeking more
accurate measure:
http://www.economist.com/news/leaders/21569417-
kilogram-it-seems-no-longer-kilogram-paris-worth-mass)
❑ Copies are kept in many other countries.
❑ Yao Ming is 141 kg, equivalent to
weight of 141 pieces of the alloy
cylinder.
January 22-25, 2013
Length, Mass, Time
January 22-25, 2013
Prefixes for SI Units
❑ 3,000 m = 3 * 1,000 m 10x Prefix Symbol
= 3 * 103 m = 3 km x=18 exa E
❑ 1,000,000,000 = 109 = 1G
15 peta P
❑ 1,000,000 = 106 = 1M
12 tera T
❑ 1,000 = 103 = 1k
9 giga G
❑ 141 kg = ? g 6 mega M
❑ 1 GB = ? Byte = ? MB 3 kilo k
If you are rusty with scientific notation, 2 hecto h
see appendix B.1 of the text 1 deca da
January 22-25, 2013
Prefixes for SI Units
10x Prefix Symbol ❑ 0.003 s = 3 0.001 s
x=-1 deci d = 3 * 10-3 s = 3 ms
❑ 0.01 = 10-2 = centi
-2 centi c
❑ 0.001 = 10-3 = milli
-3 milli m ❑ 0.000 001 = 10-6 = micro
-6 micro µ ❑ 0.000 000 001 = 10-9 = nano
-9 nano n ❑ 0.000 000 000 001 = 10-12
-12 pico p = pico = p
❑ 1 nm = ? m = ? cm
-15 femto f
❑ 3 cm = ? m = ? mm
-18 atto a
January 22-25, 2013
January 22-25, 2013
Derived Quantities and
Units
❑ Multiply and divide units just like numbers
❑ Derived quantities: area, speed, volume, density ……
◼ Area = Length * Length SI unit for area = m2
◼ Volume = Length * Length * Length SI unit for volume = m3
◼ Speed = Length / time SI unit for speed = m/s
◼ Density = Mass / Volume SI unit for density = kg/m3
❑ In 2008 Olympic Game, Usain Bolt sets world record at
9.69 s in Men’s 100 m Final. What is his average speed ?
100 m 100 m
speed = = = 10.32 m/s
9.69 s 9.69 s
January 22-25, 2013
Other Unit System
❑ U.S. customary system: foot, slug, second
❑ Cgs system: cm, gram, second
❑ We will use SI units in this course, but it is useful to
know conversions between systems.
◼ 1 mile = 1609 m = 1.609 km 1 ft = 0.3048 m = 30.48 cm
◼ 1 m = 39.37 in. = 3.281 ft 1 in. = 0.0254 m = 2.54 cm
◼ 1 lb = 0.465 kg 1 oz = 28.35 g 1 slug = 14.59 kg
◼ 1 day = 24 hours = 24 * 60 minutes = 24 * 60 * 60 seconds
◼ More can be found in Appendices A & D in your textbook.
January 22-25, 2013
Unit Conversion
❑ Example: Is he speeding ?
◼ On the garden state parkway of New Jersey, a car is traveling at a
speed of 38.0 m/s. Is the driver exceeding the speed limit of 75mi/h?
◼ Since the speed limit is in miles/hour (mph), we need to convert the
units of m/s to mph. Take it in two steps.
◼ Step 1: Convert m to miles. Since 1 mile = 1609 m, we have two
possible conversion factors, 1 mile/1609 m = 6.215x10-4 mile/m, or
1609 m/1 mile = 1609 m/mile. What are the units of these conversion
factors?
◼ Since we want to convert m to mile, we want the m units to cancel =>
multiply by first factor:
◼ Step 2: Convert s to hours. Since 1 hr = 3600 s, again we could have 1
hr/3600 s = 2.778x10-4 hr/s, or 3600 s/hr.
◼ Since we want to convert s to hr, we want the s units to cancel =>
m 1mile 38.0 mile
38.0 = = 2.36 10-2 mile/s
s 1609 m 1609 s
mile 3600 s
38.0 m/s = 2.36 10-2 = 85.0 mile/hr = 85.0 mph
s hr
1 mph =0.44704 m/s
Usain Bolt set a new world record of 9.58 seconds in the men's 100m at the 2009
World Championships in Berlin, a speed of 23.3 mph (10.416 m/s).
Mark Webber had the highest average speed of 119.61 mph in his Red Bull at
F1's Hungarian Grand Prix in July.
Mallard, a Class A4 steam locomotive, set the steam locomotion land speed
record - 125.88 mph - on 3 July 1938.
Fred Marriott has held the current land speed record for steam-powered vehicles
since 1906, when he reached 127.659 mph in his Stanley car.
The British Steam Car team say their car has reached 137.14 mph in testing, but
this is an unofficial figure. They hope to reach up to 170 mph in their record
attempt (indicated by yellow bar).
British-built Thrust SSC set the world land speed record in October 1997,
reaching 763.035 mph in a desert in the US state of Nevada.
The speed of sound changes according to factors including temperature and
altitude, but a standard figure given is roughly 768 mph.
6 Animals Faster Than Usain Bolt 1. North African Ostrich
It’s well known that Jamaican sprinter 40 mph
and 100m world record holder, Usain
Bolt, is the fastest human on Earth. But
how does he compare to his speedy
animal counterparts? Bolt’s world
record of 9.58 seconds for the 100m
race in Berlin 2009 places him at a top
speed of 30 mph with an average speed
of 23.5 mph. However, these six
animals listed from slowest to fastest, 2. Greyhound
leave him in the dust, reaching double 43 mph
and even triple the top speeds that Bolt
would only dream of ever achieving.
When it comes to speed efficiency, Bolt
could learn a thing or two from his
furry friends.
4. Pronghorn Antelope
55 mph
3. Thoroughbred Racehorse
55mph
5. Cheetah
61 mph
On June 20, 2012 she ran 100m in 5.95
seconds with a top speed of 61 mph. That’s
nearly 4 seconds faster than Bolt’s 100m world
record and more than double his top speed.
6. Peregrine Falcon
161 mph
Faster than a sports
car, this small predator
can reach up to a top
speed of 161 mph.
That’s five times faster
than Bolt’s top speed.
Dimensions, Units and
Equations
❑ Quantities have dimensions:
◼ Length – L, Mass – M, and Time - T
❑ Quantities have units: Length – m, Mass – kg,
Time – s
❑ To refer to the dimension of a quantity, use
square brackets, e.g. [F] means dimensions of
force.
Quantity Area Volume Speed Acceleration
Dimension [A] = L2 [V] = L3 [v] = L/T [a] = L/T2
SI Units m2 m3 m/s m/s2
January 22-25, 2013
Dimensional Analysis
❑ Necessary either to derive a math expression, or equation
or to check its correctness.
❑ Quantities can be added/subtracted only if they have the
same dimensions.
❑ The terms of both sides of an equation must have the
same dimensions.
◼ a, b, and c have units of meters, s = a, what is [s] ?
◼ a, b, and c have units of meters, s = a + b, what is [s] ?
◼ a, b, and c have units of meters, s = (2a + b)b, what is [s] ?
◼ a, b, and c have units of meters, s = (a + b)3/c, what is [s] ?
◼ a, b, and c have units of meters, s = (3a + 4b)1/2/9c2, what is [s] ?
January 22-25, 2013
2.3 miles -> cm?
1 mile=5,280 ft , 1ft=12 in , 1 in=2.54
cm
❑ Example 1:
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❑ Example 2:
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❑ Example 3:
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❑ Example 4:
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❑ Example 5:
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❑ Example 6:
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❑ Example 7:
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❑ Example 8:
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❑ Example 9:
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❑ Example 10:
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1 mile = 1609 m
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Summary
❑ The three fundamental physical dimensions of
mechanics are length, mass and time, which in the SI
system have the units meter (m), kilogram (kg), and
second (s), respectively
❑ The method of dimensional analysis is very powerful in
solving physics problems.
❑ Units in physics equations must always be consistent.
Converting units is a matter of multiplying the given
quantity by a fraction, with one unit in the numerator
and its equivalent in the other units in the denominator,
arranged so the unwanted units in the given quantity
are cancelled out in favor of the desired units.
January 22-25, 2013
