taks physics review day 1 objective 5 - physics force and motion force and motion newton’s laws...
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Objective 5 - Objective 5 - PhysicsPhysics
Force and motionForce and motionNewton’s lawsNewton’s lawsWavesWavesConservation of energyConservation of energyHeat transferHeat transferElectrical circuitsElectrical circuitsSimple MachinesSimple Machines
Motion: SpeedMotion: Speed Speed (S)Speed (S) - - a distance traveled in a a distance traveled in a
given amount of time. given amount of time.
LOOKLOOK at the formula on your chart: at the formula on your chart:
Speed = Distance TraveledTime
In other Words: Speed is just the distance traveled over time.
Speed Example: I.4A 10Speed Example: I.4A 10thth Spring 2003Spring 2003
First let’s list what we know and what we want to find out.
We know: Distance traveled= 150 kmTime =2.5 Hours
We want to find out: ??Average speed???
So what is the difference So what is the difference between speed and velocity?between speed and velocity?
Velocity is the vector quantity of Velocity is the vector quantity of speed. speed.
Remember:Remember: a vector needs to have a a vector needs to have a magnitude and direction.magnitude and direction.
Therefore:Therefore: Velocity is just the speed Velocity is just the speed (magnitude) in a given direction.(magnitude) in a given direction.
Let’s come up with some examples!!!
Motion: Motion: AccelerationAcceleration
When an object's velocity changes, it When an object's velocity changes, it accelerates. accelerates. AccelerationAcceleration shows the shows the change in velocity in a unit time. change in velocity in a unit time.
Let’s look at the formula:
Acceleration = final velocity – initial velocity
change in timeIn words: Acceleration is just the change of velocity over a period of time.
ExampleExample
A roller coaster has a velocity of 3 m/s and A roller coaster has a velocity of 3 m/s and an acceleration of 15 m/san acceleration of 15 m/s22. How many . How many seconds will it take the roller coaster to seconds will it take the roller coaster to reach its maximum velocity of 27 m/s?reach its maximum velocity of 27 m/s?
First let’s list what we know and what we want to find out.
We know:The current (or initial) velocity: 3 m/s, viThe acceleration: 15 m/s2, aThe maximum (or final) velocity: 27 m/s, vf
We want to find out how much time it will take the roller coaster to accelerate from 3 m/s to 27 m/s.
timeinchange
velocityinitialvelocityfinalonaccelerati
We need to solve for time so we need to rearrange our formula and solve for change in time.First:
acceleration x change in time = final velocity – initial velocity
Then solve for time:
change in time = final velocity – initial velocity
acceleration
SOLVE IT!!!
Motion: Motion: MomentumMomentumObjects in motion are said to have a momentum. Objects in motion are said to have a momentum.
This momentum is a vector. It has a size and a This momentum is a vector. It has a size and a direction. momentum is equal to the mass of direction. momentum is equal to the mass of the object multiplied by the object's velocity. the object multiplied by the object's velocity. The direction of the momentum is the same as The direction of the momentum is the same as the direction of the object's velocity. the direction of the object's velocity.
From our formula chart:
Momentum = mass x velocity
MomentumMomentum Momentum is a conserved quantity in Momentum is a conserved quantity in
physics. physics. One object might change momentum, say One object might change momentum, say
losing some momentum, as another object losing some momentum, as another object changes momentum in an opposite changes momentum in an opposite manner, picking up the momentum that manner, picking up the momentum that was lost by the first.was lost by the first.
ρ1= ρ2
therefore
m1v1 = m2v2
ExampleExample
7. The 500 g cart is moving in a straight line at a constant speed of 2 m/s. Which of the following must the 250 g toy car have in order tomaintain the same momentum as the cart?
F An acceleration of 5 m/s2 for 2 seconds G A potential energy of 20 J H A constant velocity of 4 m/s J An applied force of 5 N for 5 seconds
Newton’s LawsNewton’s LawsNewton's First Law of motion Newton's First Law of motion
(Law of Inertia)(Law of Inertia) An object at rest tends to stay at rest and an An object at rest tends to stay at rest and an
object in motion tends to stay in motion with the object in motion tends to stay in motion with the same speed and in the same direction same speed and in the same direction unless acted upon by an unbalanced forceunless acted upon by an unbalanced force. .
Newton’s Laws cont.Newton’s Laws cont.Newton's second Law of motionNewton's second Law of motion
(Law of acceleration)(Law of acceleration) The second law states that the The second law states that the
acceleration of an object is acceleration of an object is dependent upon two variables – dependent upon two variables –
the the net forcenet force acting upon acting upon
the object and the massthe object and the mass
of the object. of the object.
Newton’s Laws cont.Newton’s Laws cont.
Newton's third Law of motionNewton's third Law of motion
(Law of action and reaction)(Law of action and reaction) For every action, there is an equal and For every action, there is an equal and
opposite reactionopposite reaction
Back to our Formula ChartBack to our Formula Chart ForceForce - - a push or a pull on an object a push or a pull on an object
that will result in the acceleration of that will result in the acceleration of the object. F = ma the object. F = ma
Force is measured in Force is measured in
NEWTONS (N)NEWTONS (N)
A A newtonnewton is simply a is simply a
kg*mkg*m
ss22
Formula Chart contd.Formula Chart contd.
WorkWork - - occurs when a force causes an object occurs when a force causes an object to move in the direction of the force to move in the direction of the force
W=Fd W=Fd
Work is measured in Work is measured in
JOULES (J)JOULES (J)
A A joulejoule is simply a newton*meter is simply a newton*meter
Formula Chart cont.Formula Chart cont.PowerPower - - The amount of work that gets The amount of work that gets
done over a certain amount of time. done over a certain amount of time.
P=P= W_ W_ t tPower is measured inPower is measured in
WATTS (W)WATTS (W)
A A wattwatt is simply a is simply a joulejoule
s
Formula Chart cont.Formula Chart cont.
%efficiency%efficiency is simply the relation of is simply the relation of how much work are you getting out how much work are you getting out related to how much work you related to how much work you actually put into a process.actually put into a process.
From our chart:From our chart:
%efficiency = %efficiency = work outputwork output
work inputwork inputX 100
Sample ProblemsSample Problems
1.1. You must exert a force of 4.5 N on a You must exert a force of 4.5 N on a book to slide it across a table. If you book to slide it across a table. If you do 2.7 J of work in the process, how do 2.7 J of work in the process, how far have you moved the book?far have you moved the book?
a. .30 ma. .30 m
b. .79 mb. .79 m
c. .60 mc. .60 m
d. 1 md. 1 m
EnergyEnergy
Is defined as the Is defined as the Ability to do Ability to do WorkWork
There are two There are two Types: Types:
Kinetic (Energy of Motion) Kinetic (Energy of Motion) and and Potential (Stored Energy)Potential (Stored Energy)
Kinetic EnergyKinetic Energy
KE = ½ m v KE = ½ m v 22 Ex: A moving car Ex: A moving car has the ability to has the ability to
do work on the do work on the light pole if it hits light pole if it hits it.it.
Potential EnergyPotential Energy 2 possibilities2 possibilities
Gravitational PEGravitational PE - -Object lifted to Object lifted to some height some height
Elastic PEElastic PE - A - A stretched or stretched or compressed compressed object (spring or object (spring or rubber band)rubber band)
Gravitational Potential Energy Gravitational Potential Energy or or WiWill it fallll it fall??
GPE = m g h GPE = m g h
mm is the mass of the is the mass of the
object in Kg, object in Kg,
g is the acceleration g is the acceleration
due to gravity which is due to gravity which is
9.8 m/s9.8 m/s22 on earth and on earth and
hh is the height in is the height in metersmeters
Use the formula page! Use the formula page! PE = mgh PE = mgh
41 41 What is the What is the potential potential energy of the energy of the rock?rock?
A A 59,900 joules59,900 joules
B B 64,600 joules64,600 joules
CC 93,100 joules 93,100 joules
D D 121,600 joules 121,600 joules
m = 95 kg g = 9.8 m/s2 h = 100 m
95 kg x 9.8 m/s2 x 100 =
93,100 joules C
Law of Conservation of Law of Conservation of EnergyEnergy
Energy can change Energy can change forms, but is never forms, but is never created nor destroyedcreated nor destroyed
Loss in one form = gain Loss in one form = gain in an another form in an another form
A falling object speeds up A falling object speeds up as it falls to the ground; as it falls to the ground; PE decreases as KE PE decreases as KE increases. The KE it has increases. The KE it has at impact = the PE it had at impact = the PE it had before it fell. before it fell.
Example: A falling object Example: A falling object speeds up as it falls to the speeds up as it falls to the
ground; ground;
PE decreases as KE PE decreases as KE increases, the KE increases, the KE it has at impact it has at impact with the ground is with the ground is equal to the PE it equal to the PE it had before it fellhad before it fell
Waves - Energy carried by Waves - Energy carried by rhythmic disturbancesrhythmic disturbances
Two types:Two types: 1. E.M. radiation 1. E.M. radiation
move through move through empty spaceempty space
2. Mechanical 2. Mechanical require a medium require a medium (air, water or any (air, water or any type of matter) type of matter) for movementfor movement
All waves have similar All waves have similar propertiesproperties
FrequencyFrequency- the number of vibrations - the number of vibrations per second or the speed of the per second or the speed of the movement of the vibrating particlesmovement of the vibrating particles
AmplitudeAmplitude – the size of the movement – the size of the movement of the vibrating particlesof the vibrating particles
Both are controlled by the disturbance Both are controlled by the disturbance that created the wavesthat created the waves
Velocity of all waves - Velocity of all waves - v=f λv=f λ
f-frequency and λ is f-frequency and λ is wavelength (distance wavelength (distance between identical points between identical points on two consecutive waves) on two consecutive waves)
ReflectionReflection- bounce off - bounce off barriers in regular waysbarriers in regular ways
RefractionRefraction- waves can - waves can change direction when change direction when speed changesspeed changes
The The speedspeed of a wave is the distance the of a wave is the distance the wave travels in one unit of time. The wave travels in one unit of time. The speed of a wave is measured in units per speed of a wave is measured in units per second (m/s). A waves velocity is its speed second (m/s). A waves velocity is its speed in a particular direction.in a particular direction.
FrequencyFrequency is a measure of how many is a measure of how many wavelengths pass a particular point in one wavelengths pass a particular point in one unit of time. Measured in unit of time. Measured in hertzhertz (hz). One (hz). One hertz is equal to one wave per second. hertz is equal to one wave per second.
-So, if four complete wavelengths -So, if four complete wavelengths pass you every second, the frequency is pass you every second, the frequency is four waves per second, or four four waves per second, or four hertzhertz..
And the answer And the answer is?is?
38 38 At 0°C sound travels through air at a At 0°C sound travels through air at a speed of 330 m/s. If a sound wave is speed of 330 m/s. If a sound wave is produced with a wavelength of 0.10 m, produced with a wavelength of 0.10 m, what is the wave’s frequency?what is the wave’s frequency?
F F 0.0033 Hz0.0033 Hz
G G 33 Hz33 Hz
H H 330 Hz330 Hz
JJ 3300 Hz 3300 Hz
Use the formula chart!!!
Velocity = f λ OR f λ OR
330 m/s = f x 0.10 m330 m/s = f x 0.10 m
JJ 3300 Hz 3300 Hz
Transverse WavesTransverse Waves
In Transverse Waves In Transverse Waves particles vibrate at right particles vibrate at right angles to the direction angles to the direction the wave travels.the wave travels.
Ex. E. M. Waves, waves Ex. E. M. Waves, waves on a slinky or rope coil, on a slinky or rope coil, ocean wavesocean waves
Longitudinal or Longitudinal or Compress ional WavesCompress ional Waves
Vibrating particles Vibrating particles move back and move back and forth along the forth along the direction of the direction of the wave velocitywave velocity
Parts consist of Parts consist of compressions and compressions and rarefactionsrarefactions
Ex. Sound WavesEx. Sound Waves
Sound Waves move Sound Waves move through matter not through through matter not through
empty space. empty space. 32 32 One tuning fork is struck and One tuning fork is struck and
placed next to an identical fork. The placed next to an identical fork. The two forks do not touch. The second two forks do not touch. The second tuning fork starts to vibrate because tuning fork starts to vibrate because of —of —
F F interferenceinterference
G G the Doppler effectthe Doppler effect
HH resonance resonance
J J standing wavesstanding waves
Resonance is the vibration of another object struck by a wave of the correct frequency. Since the forks are identical, the second one receives the correct frequency to begin vibrating.
Heat TransferHeat Transfer DifferenceDifference between between HeatHeat and and
TemperatuteTemperatute..
HeatHeat is energy that is transported from is energy that is transported from warmer objects to colder objects.warmer objects to colder objects.
Temperature Temperature is a measure of the is a measure of the amount of kinetic energy and amount of kinetic energy and momentum atoms and molecules momentum atoms and molecules have in an amount of gas, liquid, or have in an amount of gas, liquid, or solid.solid.
transfer of heat through a transfer of heat through a SOLIDSOLID, , where kinetic energy is transferred where kinetic energy is transferred from molecule to moleculefrom molecule to molecule
Objects MUST touchObjects MUST touch– THINK of a CONDUCTORTHINK of a CONDUCTOR
Convection:Convection: transfer of heat that transfer of heat that occurs from the occurs from the motion of fluid in motion of fluid in LIQUIDLIQUID or or GASGAS that is that is caused by differences caused by differences in temperaturein temperature
transfer of heat by electromagnetic transfer of heat by electromagnetic WAVES WAVES that are produced by thermal that are produced by thermal motion of molecules and atomsmotion of molecules and atoms
SUN!!!SUN!!! NO TOUCHINGNO TOUCHING
Electrical Energy - Electrical Energy - Moving electrons in a Moving electrons in a
path is electricitypath is electricity Electrical Potential Difference (v) is measured in Volts Electrical Potential Difference (v) is measured in Volts The rate of moving electric charges, Electric Current The rate of moving electric charges, Electric Current
(I), is measured in Amperes (I), is measured in Amperes Resistance or opposition to the movement of the Resistance or opposition to the movement of the
energy is called Resistance (R). energy is called Resistance (R).
Circuits – 2 types Circuits – 2 types
Series circuitsSeries circuits are are the most simple. the most simple.
One (1) path for the One (1) path for the current to travel. current to travel.
Contains an energy Contains an energy source, a path, and source, a path, and a load (something a load (something for it to do, like a for it to do, like a lamp) lamp)
Circuits – 2 typesCircuits – 2 types Parallel circuitsParallel circuits
provide more provide more than one path than one path for the current for the current to travel. to travel.
Most circuits Most circuits are parallel, are parallel, since if one since if one lamp goes out, lamp goes out, the others can the others can stay lit. stay lit.
F. QG. RH. SJ. T
6. Which switches, if opened, will cause the light bulb to stop
glowing?
It is the only switch in series to both the battery and light.
USE THE FORMULA SHEET!!USE THE FORMULA SHEET!!
What is the current in a copper wire What is the current in a copper wire that has a resistance of 2 ohms and that has a resistance of 2 ohms and is connected to a 9 volt electrical is connected to a 9 volt electrical source?source?
A. 0.22 ampA. 0.22 amp
B. 4.5 ampsB. 4.5 amps
C. 11.0 ampsC. 11.0 amps
D. 18.0 ampsD. 18.0 amps
V = I R so,
9V = I x 2 ohms or 4.5 amps