PHYSICS STUDY GUIDE
CHAPTER 1: INTRODUCTION TO PHYSICS
TOPICS:
 Introduction to physics
 Physical quantities: t, d, dx, dx
 Reference frames
 Motion diagrams
WHAT YOU MUST KNOW
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Understand that Physics studies models of real life
Understand what a system is and be able to identify it
Be able to understand that models are limited
Know what a particle is and be able to identify it
Be able to identify and understand magnitude
Be able to identify and understand direction
Be able to differentiate between feeling/emotion from a physical quantity
Be able to identify and understand different units of measurements and apply them and their
symbols
Be able to identify and understand what a reference frame is
Be able to identify and understand the 3 components of a reference frame
Know and be able to identify 2 types of physical quantities: vectors and scalars
Understand what motion is and identify
Be able to understand what Delta is and its symbol ()
Be able to understand and differentiate physical quantities such as:
 clock reading (t)
 distance (d)
 position (dx)
 displacement (dx)
Be able to understand and calculate a displacement between two different positions.
Be able to understand and graph a motion diagram.
CHAPTER SUMMARY
PHYSICS
 Physics studies MODELS of real life situations.
 MODELS are not perfect and are limited.
SKETCH
 “Sketch the situation” means to draw what is happening in a specific situation.
SYSTEM
 A system is the object of interest that we choose to analyze.
 We circle the system to identify it.
PARTICLE MODEL
 In physics we are going to MODEL (convert) real objects as particles.
 We understand “particle” as a dimensionless object.
 A particle is a MODEL of a REAL OBJECT. We consider a real object to be a dimensionless particle
under two circumstances:
 When all parts of an object move in the same direction.
 When it is a tiny object (atoms & molecules).
PHYSICAL QUANTITIES
 Physical quantities are quantities that
 We can measure by using an instrument.
 Have a definite magnitude
 Have specific units of measurement
MAGNITUDE
 All physical quantities have magnitude. Magnitude is the NUMBER of the physical quantity.
DIRECTION
 The place towards which an object is directed
UNIT OF MEASUREMENT
 All physical quantities have units of measurement. A unit of measurement has been defined and
adopted by convention and/or by law, that is used as a standard for measurement of the same
physical quantity.
EXAMPLE: Let’s bake some cookies !
EXPERIMENT
INSTRUMENT
PHYSICAL
QUANTITY
MAGNITUDE
UNITS
Measure the amount of milk
Graduated Cylinder
Volume
200
mL
Measure the temperature of
the oven
Thermometer
Temperature
350
°F
Measure the baking time
Stopwatch
Clock reading
3600
Spring scale
Mass
0.5
Kilograms
Spring scale
Force
4.9
Newtons
Meter stick / ruler
length
0.05
Measure the mass of the
dough
Measure the effect of Earth on
the dough
Measure the length of your
cookies
seconds
meters
TYPES OF PHYSICAL QUANTITIES
 Physical quantities are divided in two categories:
 Vectors: physical quantities that require of a magnitude and a direction.
 Displacement
 Velocity
 Force
 Acceleration
 Momentum
 Scalars: physical quantities that only require of a magnitude.
 Mass
 Temperature
 Time intervals
 Volumes
 Speed
 Energy
 Weight
MOTION
 An object is in MOTION with respect to another object if as time progresses its position is changing
with respect to an object of reference.
REFERENCE FRAME
 A tool used by physicists to make a specific description of an object’s motion.
COMPONENTS OF A REFERENCE FRAME
 1. Starting & Ending points
 2. Coordinate axis:
 Origin
 Scale of with units and direction.
 3. Clock reading
EXAMPLE OF A REFERENCE FRAME:
A Bengal tiger walks 400 m in the negative direction in 90 seconds in the jungles of India.
dxi
-400
-350
-300
tf = 90s
-250
-200
-150
-100
-50
0
50
100
ti = 0s
PHYSICAL QUANTITIES
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CLOCK READING:
Symbol
Units
Units symbol
Type of PQ
The reading from a stop watch when an object moves between two points.
t
seconds
s
Scalar
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DISTANCE:
Symbol
Units
Units symbol
Type of PQ
How far an object is, measured from the origin.
d
meters
m
scalar
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POSITION:
Symbol
Units
Units symbol
Type of PQ
Distance and direction of an object measured from the origin.
dx
meters
m
scalar
DISTANCE VS. POSITION
 Distance and position have the same magnitude.
 Distance is a scalar (Only magnitude is needed)
 Position is a Vector (Magnitude and direction are needed.
 Distance is the magnitude of the position.
DELTA ()
 Greek letter used in science to denote a change between two physical quantities.
DISPLACEMENT
 Change in position.
 Difference between two positions.
 Final position minus initial position.
 Math model:
dx = dxf – dxi
 Symbol
dx
 Units
meters
 Units symbol
m
 Type of PQ
Vector
HOW TO CALCULATE A DISPLACEMENT
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Math model:
Substitutions:
Substitutions:
Answer with units
dx
dx
dx
dx
=
=
=
=
dxf – dxi
( -5 m ) – ( + 4 m )
-5 m – 4 m
-9 m
MOTION DIAGRAMS:
 Graphical representation used by physicists to represent the motion of an object.
 Your motion diagrams must include:
 Dots representing the position of the object at each clock reading.
 Arrows representing the direction of the motion of the object.
 Same length arrows WHEN the object is NOT increasing or decreasing speed.
 Increasing arrows when the object is increasing speed.
 Decreasing arrows when the object is decreasing speed.
 Change in v arrows: v
 v = 0 WHEN there is no change in the length of the v arrows.
 v is in the same direction of the v arrows WHEN the object is increasing speed.
 v is in the opposite direction of the v arrows WHEN the object is decreasing
speed.