Honors Physical Science
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Transcript of Honors Physical Science
HONORS PHYSICAL SCIENCE
Final Exam Review
Scientific Method
An orderly method for gaining, organizing, and applying new knowledge
Observation – 2 types Qualitative – describes qualities of
object/event Ex. Color, shape, other adjectives
Quantitative – NUMBERS! Ex. Mass, height, density, frequency
Scientific Method
Hypothesis - possible explanation based on preliminary evidence
Theory – a hypothesis/guess that has been tested repeatedly and always found to be true
Experimental Design
Experiment - evaluates alternative hypotheses Control group
You KNOW the expected outcome Helps determine if experiment ran
correctly Experimental groups
Isolate variable(s) being tested
Experimental Design
Independent Variable (IV)- variables purposefully changed or manipulated; X-axis
Dependent Variable (DV) - variable that may respond to change in Independent Variable; what you measure; Y-axis
Measurements
Metric System Based on units of 10 Used internationally and always in science Base Units:
Meter = length Liter = volume Gram = mass Kelvin = temperature Ampere = current Newton = Force
Prefixes and Scientific Notation
Mega KiloHect
oDec
a Base Unit Deci Centi Milli Micro Nano Pico
(M) (k) (h) (da)
Liter (L)Gram (g)
Meter (m) (d) c (m) ( )m (n) (p)
1000000 1000 100 10 1 1/10 1/100
1/1000
1/1000000
1/1x109 one
billionth
1/1x1012
one trillionth
Scientific NotationShorthand number writing
0.000000459 g = 4.59 x 10-7 g
Vector Quantities Has magnitude (size) Has direction Ex. Force, Velocity,
Momentum
Speed = Distance/Time Velocity = Distance/Time in a given
direction!
Mass – the amount of matter in an object Measured in g, kg, etc.
Volume – the amount of space and object takes up Measured in mL, L, cm3 etc.
Density = mass/volume Units g/cm3 or kg/L or g/mL etc.
Significant Figures
SIGNIFICANT1. All non-zero numbers (1 through 9)2. All “trapped” zeros3. END and AFTER = at the end of a number AND after the
decimal NOT SIGNIFICANT1. Place holder zeros
Multiplying & dividing - answers must contain the same number of significant figures as in the number that has the least amount of significant figures
Adding & subtracting - answers must contain the same number of digits as in the number with the greatest uncertainty (least number of decimal places)
To evaluate accuracy, you must compare your value to the correct value!
Error = experimental value – accepted value
% Error = (error ÷ accepted value) x 100
Accurate = you’re right!
Precise = a bunch of numbers are close together
Precision vs. Accuracy
Motion
Galileo Developed concept of inertia Objects fall at the same rate – SAME
ACCELERATION! Ramp – in the absence of friction ball
should reach same height
Newton’s 1st Law
Inertia - Objects at rest tend to remain at rest.
Moving objects tend to remain moving
Mass is alsoa measure of inertia!
Forces
Net Force – combination of all forces that act on an object.
Mechanical equilibrium : ∑ F = 0 The sum of the forces on the object are
zero – the object will continue doing what it is already doing
Static Equilibrium – object is at rest Dynamic Equilibrium - An object moving at
constant velocity
Newton’s 2nd Law
Force = Mass x Acceleration F = ma
Force measured in N Mass measured in kg Acceleration in m/s2
Force is directly proportional to acceleration
Related Formulas!
w = m x g Weight = mass x gravity g = acceleration due to gravity gearth= -10m/s2
a = (vf – vi)/t or a =Δv/t v = vi + at
speed of a falling object is vy = vyi + gt d= ½ at2
For a falling object d= ½ gt2
Newton’s 3rd Law
Law of Action-Reaction: Forces occur in pairs. Whenever one object exerts a force on the other, the other exerts a force equal and opposite to the first. Action and Reaction Forces ALWAYS act on
different objects Cannot have one without the other!
Momentum - Impulse
Momentum is the product of Mass and Velocity Momentum (kgm/s)= Mass (kg) x velocity
(m/s) p = mv Momentum is Inertia in motion.
Impulse = Δ p results from Δ in v or mass or both.
Greater Force = Greater Δ p
Ft = Δ mvDecrease force by increasing time of impact!
Law of Conservation of Momentum No change in momentum can occur
unless an outside force acts The net momentum before a collision will
equal the net momentum after! Go to:
http://moourl.com/collision
Collisions
Objects separate after collision
[pa + pb] before= [pa + pb]after
[ma va + mb vb]before = [ma va + mb vb]after
Objects stick together after collision
[pa + pb] before = [pa+b]after
[ma va + mb vb]before = [(ma + mb) v]after
Elastic Collisions Inelastic Collision
Don’t forget the sign (+ or - ) for direction of velocity!
These formulas will NOT be given
Work and Power
W = F * d Work = Force * Distance
Work measured in Joules, Force in Newtons, distance in meters
P = w/t Power = work / time
Power measured in watts, work in Joules, time in secs
Machines
Machines – Work in = Work out Wi = Wo Fi*di = Fo*do
Efficiency – how effective the machine is, how much energy is lost Efficiency = Wo/Wi
Efficiency = Fo*do/Fi*di Formula NOT given!
Energy
Energy-the ability to cause change or to do work
Types of energy: Potential = energy of position.
m x g x h or F x h. Kinetic = energy of motion
½ m x v2
Mechanical Energy = PE + KE
• transfer of energy always occurs when work is done!
Law of Conservation of Energy
Energy is neither created nor destroyed it simply changes forms Lost as heat Changes from KE to PE
Remember Roller Coaster and Pendulum Problems
PE converted to KE and vice versa!!
Newton’s Universal Law of Gravitation
Force and mass directly proportional
Force and distance follow the inverse square rule! Double the
distance = ¼ the force!
Projectile Motion
projectiles travel with a parabolic trajectory due to the influence of gravity,
An object thrown up will return to the ground at the same speed (opposite direction)!
Projectile Motion Formulas!
Vertical Displacement
dy = 0.5*g*t2
Horizontal Displacementdx = vix * t
Thermal Energy & Heat
Thermal Energy - The Total E (PE & KE) of all the atoms and molecules in a substance. What has more
thermal energy a cup of coffee or the ocean?
Heat is the movement of Thermal Energy
Thermal E always flows from Warmer to
cooler object.
Specific Heat Capacity
Specific heat capacity- The quantity of heat required to change the temperature of a unit mass (g) of the substance by 1 degree.
Water- high specific heat capacity. Needs a lot of heat to increase temp &takes long time to cool down (release E)
Sand will heat up and cool off much faster than water!
Heat Calculations
H or q = mcΔT H or q = heat (J) m = mass of sample(g) C = specific heat (J / g °C)
*Specific Heat of Water CH2O= 4.18 J/g°C
Δt = change in temperature (°C)
Mixed T = [m1t1+m2t2]/total mass [mass of object 1 * temperature of object 1 +
mass of object 2 * temperature of object 2] / (mass 1 + mass 2)
Heat Transfer
Conduction- transfer of heat E by the collisions between particles in a substance. ( especially solids!) Metals are good conductors due to ability to
loose electrons! Convection- transfer of heat E by the
motion of fluids. Radiation - transfer of heat by means of
electromagnetic radiation. How heat energy travels to earth!
Thermal Expansion
Bimetallic Strip One metal heats
and expands faster than the other
Metal Ring Particles expand when heated The diameter of the hole will increase
Phase Changes As heated (energy added) Solid Liquid
Gas Density decreases!
Electricity
Charge - Measured in Coulombs (C) 1 Coulomb represents a HUGE amount of charge!
p+ = 1.602 x 10-19 C e- = -1.602 x 10-19 C
Coulomb’s Law:
FE = k x (q1 x q2) ÷ r2
k = 9 x 109 Nm2/C2
*Same rules as Newton’s Universal Law of gravitation, replace mass with charge!
Current – the flow of charge, or electrons in one direction, (-)(+). Measured in Amperes (Amps, A) 1 Amp = 1 Coulomb per second
Magnetism is closely related to Electricity!
Voltage (V) – a measure of the difference in electrical potential between two parts of a circuit, or the joules of electrical work done per second (Watts) by the current.
Voltage is therefore…
Watts ÷ Amps, or…Joules (PE) ÷ Coulombs (charge)
Resistance - a measure of how strongly a wire or other substance resists current flowing through it. conductors are low resistance materials, electrical flow is
fast insulators are high resistance materials, electrical flow is
slow
Resistance is measured in OHMS, represented by Greek symbol omega (Ω).
OHMS LAW: Current (I) = voltage (V) /resistance (R)
Power = V * I Measured in Watts!
Don’t forget your engineer’s triangles!
Parallel vs. Series Circuits
Only one path through which e- flow.
(I) is the same at all points in the circuit.
(I) & (R) in a Series Circuit: R in a series circuit = sum of R
for individual devices. R for the wire is TINY so we
ignore it…Rtotal = R1 + R2 + R3…
Kirchhoff’s Law: the sum of all V drops in a system must be equal to the V battery.
Vtotal = V1 + V2 + V3…
More than one path through which e- flow; branch.
(I) splits at one or more branches
(I) & (V) in a Parallel Circuit: Kirchhoff’s Law… I in a parallel circuit = sum of
I for individual branches.Itotal = I1 + I2 + I3…
V is the same in every branch!
Rtotal = Vtotal/Itotal
Series Circuits Parallel Circuits
Waves
Wave -a disturbance or vibration that transfers energy through matter or space.
Sound- waves require a medium (solid,liquid,gas – faster through more dense material!) in which to travel . NO Medium = NO sound
Light – Waves can pass through many materials. Doesn’t require a medium Can travel through space. PURE Energy!
Wave Interactions
Reflection – wave bounces and goes in a new direction. Angle of incidence equals angle of reflection!
Refraction – the wave bends as it passes into and through the object due to a change in speed
Diffraction – The wave bends around an object or through holes in the object. More diffraction occurs through smaller openings!
Absorption – The wave is absorbed and disappears.
Sound Waves
Resonance - Result of forced vibrations in an object when the applied frequency matches the natural frequency of the object
Interference – the ability of waves to interact with each other resulting in increased or decreased effect – i.e. sounds cancel each other out
Doppler effect:
Wave Calculations
v = λf Wave speed (m/s) = wavelength (m) *
frequency (Hz or 1/s) Frequency – vibrations
or cycles/second! Amplitude is directly
proportional to Energy! Speed is inversely proportional to
wavelength and frequency!
Electromagnetic Spectrum and Light Waves
*Know these in order of wavelength and frequency!The larger wavelength the smaller the frequency!
Light Waves
Light color is determined by wavelength or frequency Light Brightness is determined by energy or
amplitude Light is additive:
Red and Blue make Magenta
Blue and Green make Cyan
Red and Green make Yellow
Complementary colors addcreate white light!
Classification of Matter
Mixtures separated based on physical properties Heterogeneous – variable composition, ex. Colloid Homogeneous – ex. solution (know solute and solvent)
Elements on periodic table Compounds – elements in fixed number ratio,
cannot be separated by physical means
Chemistry – Periodic Table & Elements
Groups are VERTICAL (#1-18) Periods are HORIZTONAL (#1-7) give Energy Level
METALS to the left NONMETALS to the right METALLOIDS the steps (middle) NOBLE GASES group #18
Atomic number: # p+ in nucleus,above symbol
Average atomic mass: amu or g/mole, below symbol
Mass Number = protons + neutrons # of neutrons = mass number – atomic number
(protons)
Isotopes and Ions
Isotopes - Atoms of the same element that differ in number of neutrons
If you change the protons, you change the element! Protons determine the element!
Ion - charged particle, protons ≠ electronsCation – lost electrons,
become positiveAnion – Gain electrons,
become negative
Electrons
Exist in energy levels Indicated by period (row) of PT More energy levels the larger the
atom Valence electrons - the
electrons on the outer most energy level and are directly responsible for the chemical properties of the element (involved in bonding) Lewis Dot Structures Atoms “want” full outermost
energy level
Bonding and Electronegativity Ionic Bond –
One atom donates and the other gains electrons
Results in opposite charges Atoms attracted to
eachother
Covalent bond – sharing of valence electrons between 2 atoms Forms enough to fill its outer
electron shell
Polar Covalent Compounds Based on
electronegativities Attraction of atom to electrons Increase left to right and bottom
to top of PT Resulting in slight negative
and slight positive charge of molecule
Fluids
Buoyancy – a measure of the upward force a fluid exerts on an object that is immersed – Dependent on DENSITY!
Archimedes Principle – buoyant force is equal to the weight of the fluid displaced by the object.
Volume of displaced fluid must equal the volume of the object!
Fobject = Fb object floats (equal D) Fobject < Fb object floats (more
above, less below – lower D) Fobject > Fb object sinks (higher
D)
Pressure Increase in speed
of fluid = acceleration = Force = increased pressure!
Pressure dependent on depth only – The deeper the
object the more pressure it experiences!
Final Exam
Tuesday June 15 9:30 – 11:00 in room D25
Bring a NON-GRAPHING Calculator You may not share!
Review Party Thursday After School!