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Physics for Dummies
Transcript of Physics for Dummies
Lab Safety Rules
Do not do anything until told to do so
Follow all instructions
Don't eat drink or chew gum at all during any labs
stay where you were assigned
Know where emergency tools (i.e. fire extinguisher) are
notify the instructor if something happens
do not try to catch anything falling
wash hands after done with anything
clean your work area
Lab Safety Rules cont'd
In Case of Accident or Injury cont'd:
If chemicals touch your skin or eyes flush them with running water for at least 20 minutes.
If a fire drill occurs in the middle of a lab turn off all your equiptment and make sure the glass is no where near the edge.
Lab Safety Rules Cont'd
Keep clothing and hair away from the hot surface
heating substances must be attended to at all times
use tongs AND insulated gloves when transporting hot equiptment
when using flammable substances make sure you know how to extinguish in case of a fire
Appropriate Lab Clothing:
goggles (only if you are working with glassware heat or chemicals) must stay on the whole time
baggy clothing, dangling earings, and long hair being down are not allowed
shoes must cover feet completley
In Case of Accident or Injury:
Report immediatley (if your lab partner is hurt you are responsible for getting the instructor's attention)
If it is spilled chemicals or broken glass notify the instructor, and make sure no one has any injuries because of it
Do not smell, taste, or touch unless your instructor tells you to.
do not use more than required (check the label)
Dispose after use
do not remove from the laboratory.
Handling Glassware and Equiptment:
if glass is broken do not touch with your bare hands
wait for hot glass to cool down before you put it into cold water, the glass could shatter
dont use chipped or cracked glass (make sure your instructor knows that the glass is chipped or cracked
dont handle electric equiptment unless your hands are clean and dry.
if you dont know how to use a piece of equiptment read instructions then ask your instructor before starting.
EVERYONE IS RESPONSIBLE!!!
Miscellaneous Safety Rules:
Keep the laboratory clean and organized
P-A-S-S (operations of fire extinguisher) :
P - Pull the pan
A - Aim the hose at the base of the fire from 5-6 ft away
S - Squeeze the handle
S - Sweep the hose back and forth across the fire
Lab Safety Symbols:
Animal Safety: used when live animals are being studied
Disposal Alert: appears when care must be taken when disposing materials.
Fire Safety: means to be careful around open flames
Eye Safety: occurs when possible damage to your eyes can happen
Sharp Object Safety: appears when danger of cuts or puncture is possible
Poision Safety: when poisioness
substances are being used
Electrical Safety: use care when handling electrical equiptment
Open Flame Alert: when usinf an open flame it could cause a fire or explosion
Lab Safety Symbols cont'd
Plant Safety: poisionous or plants with thorns are being handled
Chemical Safety: when chemicals can cause burns or are poisionous if it comes in contact with the skin
Radioactive Safety: when radioactive substances are being used
Biological Safety: There is danger
involving bacteria, fungi, or protists.
Fume Safety: chemicals or chemical reactions
could cause bad/dangerous fumes.
Clothing Protection Safety: substances used could possibly burn or stain clothing
Explosion Safety: missuse of chemicals could cause an explosion
Thermal Safety: use caution when handling hot objects
holds liquid for testing
holds liquid while stiring or heatings. it can also measure liquid.
Test Tube Holders:
hold test tubes
also measures volume
Lab Equiptment cont'd
Triple Beam Balance:
measures mass and weight
measures weight and mass
Mortar and Pestle:
Lab Euiptment cont'd
protect your clothes
The Scientific Method
Basically it is an organized science experiment.
1.) Observation - use the five senses to get some information
2.) Problem - what do you want to know, or what do you want to accomplish
3.)Hypothesis - edicated guess
4.)Data Collection - the actual experiment, you are testing the hypothesis.
5.)Analyze - explain with your word, graphs, and/or charts
6.)Draw Conclucion - conclude if your hypothesis was correct or incorrect and explain why.
A controlled experiment is an experiment in
which one variable must stay the same.
There are three types:
-Independent Variable - meaning it is manipulated
-Dependent Variable - meaning it responds
-Controlled - meaning it is constant
You can analyze any data by using graphs or charts as a visual display of your information.
Types of Graphs:
-Pie Graph - breakdown of your information (100%)
-Bar Graph - compares different objects
-Data Table - a chart that organizes all of your data
-Line Graph - relationships between variables
SI Units and Metric Conversions
SI=Internationa;l System of Units
worldwide communication for scientists
Base units include: gram (g) ; meter (m) ; liter (L)
(kilo) (hecto) (deka) (base units (deci) (centi) (milli)
m, L, g)
K H D B D C M
Convert .00900 kg to millimeters.
.00900 kg = 9,000mm
Metric Conversions cont'd
1.) Determine the starting point
2.)Count the jumps to the end point
3.)move the decimal as many times as you jumped, and in the same direction
It makes numbers easier to work with.
It has two parts:
1.) a number between 1 and 9.999
2.) a power of 10
2.0 x 10^6
The exponent 6 means that the decimal is actually 6 places to the right of the 2.
Scientific notation is changed back to its original form.
2.0 x 10^6 = .000002
The exponent 6 means the decimal was moved 6 places to the left.
Time: interval betwtwo events.
SI unit is in seconds
stopwatch or CPO timer is the object used to measure time.
Temperature: How hot/cold something is
SI unit is Kelvin (K)
0 K = 273 degrees celcius (c) = absolute zero
to change celcius to Kelvin add 273 and vice versa
thermometer is the object used to measure temperature
Length: distance between two points
SI unit is meters (m)
Rulers or meter sticks is the object(s) used to measure length.
the ruler is the tool that is used
SI unit is cubic centimeters (cm^3)
multiply length x width x height
Volume: Liquids: the amount of space occupied by an object
the graduated cylinder is the tool that is used
SI unit is milliliters (mL)
volume of irregularly shaped objects require the water displacement method.
ex.) amount of H2O with object = 270mL
amount of H2O without object = 200mL
difference = 70 mL
SI Units cont'd
amount of matter in the object
SI unit = kilogram (kg) (gram (g) if smaller)
a balance scale is the scale used
ratio of mass per unit of volume
SI Units include:
solid = g/cm^3
liquid = g/mL
Density is a derived unit
G - givens
U - unknown
E - equation
S - substitue
S - solve
Example of Density:
D=? g/mL D=m g/mL= 100g D=5m/mL
v=20mL v 20mL
States of Matter
Definite shape and volume
the particles are packed really close together, they vibrate not moving out of there original position, and solids have the highest potential energy.
the volume is defined, but the shape isnt defined
Whatever container it is in, it will take that shape.
the particles are kind of close together, and there is not an exact arrangement.
the volume and shape is not defined.
the volume and the shape both depend on the container it is in
the particles are spread out, they usually expand and contract, gases have the highest kinetic energy.
Physical change is reversable most of the time. This only happens when the state of matter is changed. Energy is either absorbed or released in this process.
Endothermic - feels cold, and energy is absorbed.
Exothermic - feels hot,
and energy is released.
Heat of Fusion:
Heat of fusion is the amount of energy needed to change from a solid to a liquid, freezing/melting point.
Heat of vaporization is the amount of energy needed to change from a liquid to a gas, boiling/condensation point.
Heat of Vaporization:
Matter is either a pure substance or mixtures.
Matter that has the exact same composition all the time is called a pure substance. some examples of a pure substance include: Gold, Salt, and Sugar
The two types of pure substances include;
compounds - 2 or more elements make this up, and they are always joined in a fixed proportion.
elements - is not able to be broken down, and the smallest particle of an element is an atom.
Examples of elements:
carbon, platinum, and mercury.
Examples of compounds:
water, salt, steam
Mixtures do not have a fixed composition.
kool-aid, M&M's, Chex-Mix
The two types of mixtures include:
Homogeneous, which is when the substances are evenly spread out/ distributed. AKA solutions (substances are dissolved) ex.) vinegar
Heterogeneous, which is when there are noticeably different parts. There are two different types of Heterogeneous mixtures:
Colloids - scattered, they never settle. Ex) fog
Suspensions - visible particles settle, the mixture eventually seperates. Ex) Italian dressing
Filtration - seperates the mixture depending on the particle size. Ex) coffee
Distillation - Depending on the boiling point of the material, the mixture is seperated.
Ex) salt water
You can observe it wit changing the actual substance.
The change doesn't change the substances in the material, it only changes the looks.
The ability to chemically change. Ex) something being flammable.
react with light (fading) / oxygen (rust) / water/ acid
Precipitate is able to form.
Changes a substance into a completley new substance.
Law of Conservation of Mass:
In its most basic definition matter is not created nor destroyed.
Electron - e- , has a negative charge, is found outside of the nucleus.
Proton - p+ , has a positive charge, is found inside of the nucleus.
Neutron - n^o, has no/neutral charge, it is found inside the nucleus.
The nucleus has the most mass of an atom.
Electrons=1/2000th of the mass of a proton.
Atomic Mass Number/
To find proton number, use the atomic number
To find electron number, use the proton number
To find neutron number, subtract the atomic number from the mass number.
p+ = 10
e- = 10
n^o = 20 (rounded) - 10 = 10
Protons give an atom its identity.
The mass number of an Isotope changes because of the different number of neutrons. The atomic number however remains the same.
Carbon-12: has 6 protons and 6 neutrons.
Carbon-13: has 6 protons and 7 neutrons.
Carbon-14: has 6 protons, and 8 neutrons.
How to Write a Nuclide:
Atomic number is the subscript, and the mass number is the superscript, with the element symbol on the outside. Example:
An orbital is an energy level where electrons are commonly found. an electron iguration is how the electrons are arranged.
Energy level Electron Capacity
Drawing Bohr Models:
1.) Draw the nucleus
2.)Write the neutron and proton number in the center of the nucleus.
3.)Draw the energy levels on the outside of the nucleus.
4.)Draw the appropriate amount of electrons on each energy level.
Chemically Stable Atoms:
If the outer energy level is completley filled, or it has 8 valence electrons, then an atom is considered chemically stable.
*ALL Nobel gases are chemically stable*
A reaction process then occurs to fill the outer energy level.
The valence electron is represented by the group number. chemical properties depend on the number of valence electrons.
Electron Dot Diagram:
Each dot represents a valence electron.
How to write them:
write the symbol
put a dot for each valence electron
don't pair up until each side has a dot.
The electron dot diagram for chlorine shown to the left shows that, there are seven dots to represent that chlorine has seven valence electrons.
Ratios are the amount of ms for each element.
Bonding happens with interaction of valence electrons.
The only reason they react is because they want to all have a full outer energy level.
There are two ways to get a full outer energy level:
Types of Bonds:
Ionic Bonds - metal and non-metal (transfer electron)
Covalent Bonds - 2 nonmetals (share electrons) (hydrgogen is a covalent bond) (called molecules) (the most common type of bonding)
Metallic Bonds - 2 metals (sea of electrons)
Ions form when an atom gains or loses an electron, causing it to take either a positive or negative charge.
There are two types of ions:
anion: negatively charged ion (nonmetal)
cation: positively charged ion (metal)
Chemical formulas tell the elements that are in a certain compound, including the ratios.
Ex.) H2O = hydrogen, oxygen 2:1
Naming Binary Ionic Compounds:
A binary compound has 2 elements.
How to Write a Binary Compund:
1.)write the first element's name
2.)write the root of the second element, then change the end to -ide.
NaLi - Sodium lithide
CS - Carbon sulfide
CaF - Calcium flouride
Writing Formulas for Binary Ionic Compounds:
1.) Write the first and second element's SYMBOL.
2.) Find the oxidation number, which is the charge
3.) Switch the oxidation numbers leave off the charges.
Naming Polyatomic Compounds:
A polyatomic ion is a group of atoms with a positive or negative charge, it is covalently bonded.
Name Symbol Charge
Nitrate NO3 -1
Carbonate CO3 -2
Chromate CrO4 -2
Acetate C2H3O2 -1
Permanganate MnO4 -1
Hydroxide OH -1
Sulfate SO4 -2
Chlorate ClO3 -1
Phosphate PO4 -3
Ammonium NH4 +1
*A molecule is a neutral group of atoms formed together by one or more covalent bonds.
Naming Molecular Compounds:
Prefixes of Compounds:
Number of atoms Prefix
Li3PO4 = Lithium phosphate
K2NO3 = Potassium nitrate
CO2 = carbon dioxide
BF3 = boron trifluoride
CCl4 = carbon tetrachlorine
Writing Molecular Formulas:
1.) nitrogen pentachloride
2.) potassium trifluoride
Naming Chemical Compounds:
NaBr = sodium brom
MgBr2 = magnesium brom
A chemical reaction is when one or more substances are changed to a new substance.
2H2 + O2 -> 2H2O
Reactants - the substance that undeergoes the change.
Products - this the new subtances that was formeed.
Zn + Cl2 -> ZnCl2
Pb + 4HCl -> PbHCl4
Li2O + CO2 -> LiCO3
Types of Reactions:
This type of reaction is when 2 or more reactants to form one substace (one product)
2 reactants ----> 1 product
A +B --> AB
Na + Cl --> NaCl
*The product is always a compound!*
This type of reaction is when one substance (reactant) breaks down into two substances (products)
1 reactant -------> products
AB --> A + B
NaCl --> Na + Cl
*the reactant has to be a compound in order for it to perform decompisition.*
This type of reaction is when one element replaces another element.
A + BC --> AC + B
K + PS --> KS + P
*one element is replaced*
This type of reaction is when two compounds switch positively charged ions (cations) creating two new products.
AB +CD --> AD +BC
NiSe + ArK --> NiK + SeAr
This is a reaction when a substance reacts rapidly with oxygen, usually producing heat and light.
*always produces Carbon dioxide and water*
CH4 + 2O2 --> CO2 + 2H2o
How to Balance a Chemical Equation:
Cu20 + C --> Cu + CO2
Cu - 1 Cu -1
O - 2 O - 2
C - 1 2 C - 2
A solute is the dissolved particles in a solution.
Ex.) The sugar in the koolaid
The solvent is the substance in which the solute dissolves.
Ex.) The water in the koolaid
The solution is the combination of the solute and the solvent.
Substances can dissolve in three ways:
1.) Dissociation - an ionic compound sperates into ions while dissolving
2.) Dispersion - Breaking into smaller pieces
3.) Ionization - the neutral molecules will either gain or lose electrons.
Solute Solvent Solution
Water in air
Balancing Equations Practice:
H2O --> H2 + O2
H = 2 4
O = 1 2
H = 2 4
O = 2
Na + Cl2 --> NaCl
Na = 1 2
Cl = 2
Na = 1 2
Cl = 1 2
Types of solutions:
1.) Saturated Solutions - this solutions holds as much solute as the solvent can hold at a given temperature.
2.) Unsaturated Solutions - this solutions has less than the maximum amount of solute that can be dissolved.
3.) Supersaturated Solutions - holds more than the maximum amounte of solute.
Practice Identifying the types of solutions:
50g KCl / 100g H2O @ 50 degreees celcius?
75f KNO3 / 100g H2O @ 50 degrees celcius?
Factors that affect solubility:
1.) Polarity - like dissolves like
2.) Temperature - increases the solubility
3.) Pressure - Increasing pressure increases the solubility
The amount of solute dissolved in a specific amount of solution.
Formula = conc% = Solute
solute - 15mL 15mL
solvent - 100mL 115mL
(if you add those conc% = 15%
together you get
solution - 115mL
1.) solute = 30mL conc% = solute
solution = 300mL solution
conc% = ? %
conc% = 30%
2.) solute = 50mL conc% = solute
solution = 500mL solution
conc% = ? %
conc% = 50%
Table of Contents
Slides 7-9 = Lab safety rules (notes)
Slides 10-11 = Lab safety symbols (notes)
Slides 12-14 = Lab equiptment (notes)
Slide 15 = scientific method (notes)
Slide 16 -controlled experiments & SI units and metric converstions (notes)
Slide 17-18 = Metric conversions (notes and practice problems)
Slide 19 = Scientific notation and Standrd notation (notes and practice problems)
Slides 20-21 = SI units (notes and practice problem)
Slide 22 = States of matter (notes)
Slide 23 = Heat of fusion, heat of vaporization, and classifying matter (notes)
Slide 24 = Seperating mixtures, and Properties (notes)
Slide 25 = Atomic structure (notes and practice problems)
Slide 26 = Periodic table
Slide 27 = Atomic orbital, Drawing bohr models, Isotopes, and how to write a nuclide (notes and practice problems)
Slide 28 - Chemical bonds, electron dot diagram, valence electrons (notes and practice problems)
1.) convert .89 dekameters to decimeters
K H D B D C M
.89dm = 89 decimeters
1.) convert 12m to centimeters
K H D B D C M 12m = 1,200cm
1.) convert 56.12 grams to centimeters
K H D B D C M 56.12g = 5,612cm
2.) convert 72 centimeters to kilometers
K H D B D C M 72cm = .00072
1.) write the scientific notation for .004
4.0 x 10^3
2.) write the scientific notation for .00008
8.0 x 10^5
1.) write the standard notation for 3.0 x 10^4
2.) write the standard notation for 7.0 x 10^8
3.) write the standard notation for 5.1 x 10^3
4.) write the standard notation for 9.0 x 10^5
1.) D = 7mL D=m g = (7mL)(15mL)
V = 15mL v m = 105g
m = ?g
1.) Using the periodic table identify the protons neutrons, and electrons of Arsenic.
p+ = 33 n^o = 42 e- = 33
75 - 33 = 42
2.)Using the periodic table find the p+, n^o, e- of Calcium.
p+ = 20 n^o = 20 e- = 20
40 - 20 = 20
Draw the bohr model for sodium.
1.) Draw the nuclide of Magnesium.
2.) Draw the nuclide for Boron.
1.) Draw an electron dot diagram for sodium.
2.) Draw the electron dot diagram for potassium.
Table of Contents cont'd
Slide 29 = Bonding (notes and practice problems)
Slide 30 = Naming polyatomic and molecular compounds (notes and practice problems)
Slide 31 = Writing molecular formulas, naming chemical compounds, chemical equations (notes and practice problems)
Slide 32 = Types of reactions (notes)
Slide 33-34 = Balancing chemical equations, solutions (notes and practice problems)
Slide 35 = factor affacting solubility, concentration formula (notes and practice problems)
Slide 36 = Acids and bases (notes)
Slide 37-38 = Radioactivity and half life (notes and practice problems)
Slide 39 = Motion (notes and practice problems)
Slide 40 = Speed (notes and practice problems)
Slide 41 = Acceleration (notes and practice problem)
Slide 42 = Force (notes and practice problems)
Slide 43 = Weight (notes and practice problems)
reacts with metal
can conduct with electricity
range from 0-6.999 on the pH scale
turns blue litmus paper red
phenophthalein remains colorless
0-3 on the pH scale are strong acids
3.1-6.999 on the pH scale are weak acids
reacts with salt and water
phenophthalein turns pink
range from 7.1-14 on the pH scale
turns red litmus paper blue
11-14 on the pH scale are strong bases
7.1-10.999 on the pH scale are weak bases
7 IS NEUTRAL!
Radioactivity and Half Life
Radioactivity is the process in which an unstable atomic nucleus emits charged particles and energy.
Nuclear decay is when atoms of one element can change into atoms of a different element altogether.
Nuclear radiation is when charged particles and energy that are emittted from the nuclei of radioisotopes. dommon types include alpha particles, beta particles, and gamma rays.
Made up of two protons and two neutrons
The symbol is 4
mass number decreases by four, and the atomic number decreases by two.
238 234 4
92 90 2
1.) 48 44 4
22 20 2
2.) 27 23 4
13 11 2
Electron emitted by an unstable nucleus.
The symbol is 0
mass number stays the same, an the atomic number goes up by one.
234 234 0
90 91 -1
1.) 59 59 0
27 28 -1
2.) 27 27 0
13 14 -1
A penetrating ray of energy
The symbol is y
The mass number and the atomic number stay the same
Half Life cont'd
Half life is the time requried for one half of a sample of a radisotope to decay.
Number of half lives Amount of original sample remaining
How many days does it take for 16g of palladium-103 to decay to 1.0g? The half-life of palladium-103 is 17 days.
x=18.0g = 18(1/2) ^4
Motion is a change in position
A frame of reference is a system of objects that arent moving with respect to one another.
Movement is relative to a stationary object
Earth is the most common frame of reference
Motion can be described as the following:
Mathmatical quantities used to describe motion of objects:
Scalars - described by a magnitude (numerical value) alone
Vectors - both magnitude and a diraction
Distance - the length of a path between two points. The SI unit is meter (m). Distance is a scalar quantity, aka "how much ground is covered" during motion
Displacement - a vector quantity, which is how out of place the object is after motion, aka change in overall position.
Distance = 5+10+3= 18m
Displacement = 18m to the right
Distance = 3+12+6 = 21m
Displacement = 9m to the right
Speed is the ratio of the distance an object moves to the amount of time the object moves.
The SI unit is meter per second (m/s)
formula = V=d
Average speed is averaged for the entire duration of the trip.
instantaneous speed is measured at a certain instant
Velocity is the speed and diraction an object is moving.
Velocity can be changed by:
d=27m V=d =27m
t=3s t 3s
horizontal line = the objected has stopped moving
Curved line= gradual increase
straight line = constant speed
the greater the slope higher the speed.
1.) d=50m v=d = 50m
t=10s t 10s
2.) d=65m v=d =65m
t=5s t 5s
3.) d=224m v=d =224
t=12s t 12s
4.) d=26m v=d =26m
t=2s t 2s
Acceleration is the rate at which velocity changes.
changes in just speed
changes in just direction
changes in speed and direction
unit is meter per second per second (m/s^2)
Formula - a=Vf-Vi or V
Vf = final velocity (m/s)
Vi = initial velocity (m/s)
a = acceleration (m/s^2)
t = time (s)
g = 9.8m/s^2 (due to gravity on earth)
To have acceleration an object must:
speed up (positive acceleration)
slow down (negatice acceleration)
change direction in travel
There are two graphs that can represent acceleration:
To graph acceleration:
the slope of a speed-time graph represents acceleration
constant speed is represented as a straight line
slope downward shows an object slowing down (negative acceleration)
1.) Vi = 0m/s a=Vf-Vi =50m/s-0m/s
Vf = 50m/s t 10s
t = 10s
a = ?m/s^2 a=5m/s^2
a push or pull
one exerts force on another
SI unit newton (N)
measured using a spring scale
Balanced or Unbalanced:
if all the forces acting on the objecor equal then it is considered balanced (no motion)
if a force acting on an object is stronger than the others it is considered unbalanced (motion)
*Net force is the overall acting on the object after all the forced are combined.
*If the object is moving in the same direction then you add, if the object is moving in different directions then you subtract.
Net force: 0N
Net Force: 3N
a force that opposes a motion when two surfaces are touching.
The four types of friction:
1.) Static-initial friction force that acts on an object as it slides over a surface.
2.) Sliding-force opposes the direction of motion
3.) Rolling-force acts on rolling object
4.) Fluid-opposes motion of object through liquid/gas/air/water resistance
The measure of the force of gravity on an object.
Fg = gravitational force (N)
m = mass (kg)
g = gravity (9.8m/s^2)
Measured in Newtons (N)
Formula = Fg=mg
The amount of matter in an object.
Measured in grams (g)
Weight changes based on location!
Newton's Third Law:
For every action there is an equal and opposite reaction. (F=F)
1.) Tracie's 8.6kg bike is at rest on the ground. What is the force of the bike?
m=8.6kg Fg=mg =(8.6kg)(9.8m/s^2)
Fg=?N Fg = 84.28N
2.) A 30kg book sits on a table. What is the force of the book?
m=30kg Fg=mg =(30kg)(9.8m/s^2)
Table of Contents cont'd
more mass=more momentum
more velocity=more momentum
formula = p=mv
p = momentum (kg)(m/s)
m = mass (kg)
v = velocity (m/s)
Law of Conservation of Mass:
in a closed system, the loss of momentum of one object equals the gain in momentum of another object -momentum is conserved.
1.) A 13kg volleyball travels at 2.6 m/s. Calculate the momentum.
m=13kg p=mv =(13kg)(2.6m/s)
2.) A 25kg bowling ball is rolled at 6.7m/s. Calculate the momentum.
m=25kg p=mv =(25kg)(6.7m/s)
Slide 44 = Momentum (notes and practice problems)
Slides 45-46 = Machines (notes and practice problems)
machines make work easier
How machines make work easier:
raising a car on a jack
usind oars to row a boat
pulling back on the oars to row the boat
Work input and work output:
Work done on a machine is work input
Work done by the machine is work output
You cant get more work than you put in.
The number of times the machine increases an input force.
AMA = actual mechanical advantage
Fr = output force
Fe = input force
Formual = AMA=Fr
Practice problems for AMA:
1.) A machine exerts a force of 6N for each 1N of force you exert on the machine. What is the AMA of the machine?
Fr=6N AMA=Fr =6N
Fe=1N Fe 1N
2.) A machine exerts a force of 32N for each 2N of force you exert on the machine. What is the AMA of the machine?
Fr=32N AMA=Fr =32N
Fe=2N Fe 2N
AMA=? AMA= 16
IMA = ideal mechanical advantage
de = input distance
dr = output distance
Formula = IMA=de
because friction is always present AMA is always less than IMA
Practice problems for IMA:
1.) If x=6cm and y=12cm what is the IMA of the pliers?
de = 12cm IMA=de = 12cm
dr = 6cm dr 6cm
IMA = ? IMA = 2
2.) If x=8cm and y=64cm what is the IMA of the object?
de = 64cm IMA=de = 64cm
dr = 8cm dr 8cm
IMA = ? IMA = 8
no machine can be 100% efficient because friction is always present.
formula = Efficiency = wi
Energy is the ability of an object to cause change.
Basic unit is the Joule (J)
Forms of Energy:
Mechanical = PE + KE
Thermal = heat
Chemical = wood, gasoline
Electrical = lighting, batteries
Electromagnetic = visible light, x-rays
Nuclear = fission, fussion
Potential energy is
The amount depends on:
Two types of PE
Gravitational -height above earth's surface
the higher up the more PE
greater mass = more PE
Elastic - stretched or compressed (spring)
The equation is
PE = potential energy (joules (J))
m = mass (kg)
g = gravity (9.8m/s^2)
h = height (m)
1.) A 300kg boy sits on a chair 5m in the air. What is his PE?
m=300kg PE=mgh =(300kg)(9.8m/s^2)(5m)
the form of motion
greater mass = more KE
greater velocity = more KE
formula = KE=1/2mv^2
KE = kenetic energy (J)
m = mass (kg)
v = velocity (m/s)
1.) What is the kinetic energy of a jogger with a mass of 65kg traveling at a speed of 2.7m/s?
m = 65kg KE = 1/2mv^2 =(1/2)(65kg)(2.7m/s)^2
v = 2.7m/s =(1/2)(65kg)(7.29m/s)
KE = ? J KE = 236.9 J
the process of changing energy from one form to another.
Conservation of Energy:
Law of conservation of energy states that cant be creaated or destroyed.
Slides 47-48 = Energy (notes and practice problems)
Slide 49 = The pendelum (notes)
Slides 50-51 = Thermal energy and heat (notes)
Slides 52-53 = Waves (notes)
Slide54 = Wave velocity (notes and practice problems)
High PE at the top High KE at the bottom
Low PE at the bottom Low KE at the top.
*Energy is transformed*
Termal Energy and Heat
Heat is energy that flows from high temperatures to low temperatures (will flow until equilibrium is reached)
temperature - measure of KE of the particle in a sample of matter
increase temperature = greater KE
decrease temperature = lower KE
absolute zero = 0KE all particles cease
Thermal expansion and contraction;
hot temperatures cause materials to expand and vice versa
specific heat is the amount of energy need to raise the temperature on something. (the lower the specific heat the quicker the object will heat up.)
conduction is the transfer of energy through matter by DIRECT CONTACT.
convection is the transfer of energy by movement.
fluid - anything flowing
liquids and gases
radiation is the transfer of energy through electromagnetic waves .
Transfer of heat to earth is UV radiation.
shiny material reflect radiant energy.
dull, and dark absorb more
lighter colors absorb less
Thermal Energy and Heat cont'd
waves are rhythmic disturbances that carry energy through matter through space.
a medium the material that the wave travels through.
Solid, liquid, gas, or combination
Three types of Waves:
transverse wave -medium moves at a right angle to direction of wave
longitudinal wave -matter vibrates in the same direction as the wave
surface wave - the waves travels along the surface, most common being the ocean wave.
crest is the highest point above the rest point
trough is the lowest point below the rest point
wavelenght is the distance between a point on one wave to another wave
Behaivor of Waves:
interference - two or more waves overlap
constructive - waves add together ; amplitude increases
destructive - waves subtract from each other ; amplitude decreases
speed of sound depends on:
type of medium
temperature of medium (faster at higher temp)
loud annoying harmful sounds
concert walls have carpet walls to stop echos ; absorb the sound ; and to keep unwanted sound out.
a change in sound frequency caused by motion of the sound source/listener/both.
higher pitch = higher frequency and vice versa.
V = velocity (m/s)
f = frequency (Hz)
THE FORMULA IS: V=(f)(wavelength)
1.) V = ? m/s V=(f)(wavelength) =(8Hz)(60m)
f = 8Hz
wavelength = 60m V = 480m/s
2.) V = > m/s V=(f)(wavelength) =(10Hz)(75m)
f = 10Hz
wavelength = 75m V = 750m/s