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TAKS Objective 5

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4 The picture shows the position of a ball every 0.25 second on a photogram. ... Workout = 18J = 6N x 3m. Work Input = 30J done by the motor ... – PowerPoint PPT presentation

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Title: TAKS Objective 5


1
TAKS Objective 5
  • Motion , Forces
  • and Energy

2
Energy
  • Is defined as the Ability to do Work
  • Energy has Two
  • Types

Kinetic (Energy of Motion) and Potential (Stored
Energy)
3
Kinetic Energy
  • KE ½ m v 2
  • Ex A moving car has the ability to do work on
    the light pole if it hits it.

4
Potential Energy 2 possibilities
  • Gravitational PE -Object lifted to some height
  • Elastic PE - A stretched or compressed object
    )(springs

5
Gravitational Potential Energy or Will it fall?
  • GPE m g h
  • m is the mass of the
  • object in Kg,
  • g is the acceleration
  • due to gravity which is
  • 9.8 m/s2 on earth and
  • h is the height in meters

6
Use the formula page! PE mgh
  • 41 What is the potential energy of the rock?
  • A 59,900 joules
  • B 64,600 joules
  • C 93,100 joules
  • D 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
7
Law of Conservation of Energy
  • Energy can change forms, but is never created
    nor destroyed
  • Loss in one form gain in an another form
  • A falling object speeds up as it falls to the
    ground PE decreases as KE increases. The KE it
    has at impact the PE it had before it fell.

8
Example A falling object speeds up as it falls
to the ground
  • PE decreases as KE increases, the KE it has at
    impact with the ground is equal to the PE it had
    before it fell

9
Energy can be conserved in Non-Mechanical forms
  • The chemical energy in a battery transforms into
    electrical energy
  • Any reaction where more energy is given off than
    is used to start it is Exogonic
  • An Endogonic reaction absorbs energy and causes
    cooling

10
Electrical Energy - Moving electrons in a path
is electricity
  • Electrical Potential Difference (v) is measured
    in Volts
  • The rate of moving electric charges, Electric
    Current (I), is measured in Amperes
  • Resistance or opposition to the movement of the
    energy is called Resistance (R).

11
Circuits 2 types
  • Series circuits are the most simple.
  • One (1) path for the current to travel.
  • Contains an energy source, a path, and a load
    (something for it to do, like a lamp)

12
Circuits 2 types
  • Parallel circuits provide more than one path for
    the current to travel.
  • Most circuits are parallel, since if one lamp
    goes out, the others can stay lit.

13
  • Which switches, if opened, will
  • cause the light bulb to stop glowing?
  • Q
  • R
  • H. S
  • J. T

It is the only switch in series to both the
battery and light.
14
USE THE FORMULA SHEET!!
  • What is the current in a copper wire that has a
    resistance of 2 ohms and is connected to a 9 volt
    electrical source?
  • A. 0.22 amp
  • B. 4.5 amps
  • C. 11.0 amps
  • D. 18.0 amps

V I R so, 9V I x 2 ohms or 4.5 amps
15
Thermal Energy
  • A body contains internal KE due to the motion of
    its atoms ( they are constantly wiggling and
    jiggling)
  • Thermal Energy is the total internal KE of a body
  • Temperature is the average KE of a body

16
Heat- Transfer of Thermal Energy
Three forms of heating
  • 1. Conduction-direct contact, a pot heating on a
    stove
  • 2. Convection- heating by circulating fluids,
    heating from a fireplace
  • And. . .

17
3. Radiation Transfer of Electromagnetic (E.M.)
Energy
  • Objects are heated when
  • exposed to infrared radiation
  • The suns heats the earth by
  • sending infrared radiation
  • along with other forms of E.M. energy
    93,000,000 miles through empty space

18
Heat moves by conduction in solids since the
particles are close together and vibrate. . .
  • 43 Heat convection occurs in gases and liquids.
    Heat convection does not occur in solids because
    solids are unable to
  • A absorb heat by vibrating
  • B transfer heat by fluid motion
  • C emit radiation by reflecting light
  • D exchange heat by direct contact

Solids do radiate heat to their surroundings
19
2 The primary way liquids and gases transmit heat
is by the process of
  • F reflection
  • G conduction
  • H radiation
  • J convection

Fluid heat movement is convection. Fluid motion
occurs in liquids and gases.
20
50 A solar heater uses energy from the sun to
heat water. The heaters panel is painted black
to
Convection is movement of heat in fluid matter,
heat loss would be from a solid exterior Not G
  • F improve emission of infrared radiation
  • G reduce the heat loss by convection currents
  • H improve absorption of infrared radiation
  • J reduce the heaters conducting properties

Painting a substance will not change its
conductivity That is a property of metals. It
would have to be made of a different substance to
change that Not J
Emission is giving off we want to absorb Not F
21
Nuclear Reactions
  • Fusion occurs when two atoms
  • combine to form a new element.
  • The sun produces all of its
  • energy through fusion.
  • Two hydrogen atoms combine
  • to form a Helium atom from the
  • great gravitational forces and
  • pressure in the suns core

22
Nuclear Reactions - Fission
  • Fission is the splitting of nucleii of large
    atoms such as Uranium and Plutonium
  • Produces large amounts of infrared radiation and
    other forms of E.M. Energy such as Gamma Rays
  • Currently, it is the main form of Atomic Energy
    on Earth

23
Radiant Energy or Electromagnetic Energy (EM)
  • All radiant energy travels at 3.0 x 108 m/sec in
    space
  • Velocity of a wave wavelength x frequency
  • Visible light is just one type of EM Energy

24
Electromagnetic Spectrum
All of the forms of radiation given off by
vibrating electric charges
  • Radiation comes in the form
  • of vibrating or throbbing
  • bundles of energy called
  • photons
  • The frequency of the vibrating
  • electric charges determines
  • which type and how much
  • energy will be given off

25
The entire E.M. Spectrum in order from lowest to
highest frequency
  • Radio waves AM and FM
  • Microwaves cooking
  • Infrared heat
  • Visible (ROYGBV)
  • Ultraviolet tanning
  • Xrays medical
  • Gamma

deadly radioactivity
26
Waves - Energy carried by rhythmic disturbances
in space
  • Two types
  • 1. E.M. radiation move through empty space
  • 2. Mechanical require a medium (air or water) for
    movement

27
All waves have similar properties
  • Frequency- the number of vibrations per second or
    the speed of the movement of the vibrating
    particles
  • Amplitude the size of the movement of the
    vibrating particles
  • Both are controlled by the disturbance that
    created the waves

28
Velocity of all waves - vf ?
  • f-frequency and ? is wavelength (distance between
    identical points on two consecutive waves)
  • Reflection- bounce off barriers in regular ways
  • Refraction- waves can change direction when speed
    changes

29
And the answer is?
J 3300 Hz
  • 38 At 0C sound travels through air at a speed of
    330 m/s. If a sound wave is produced with a
    wavelength of 0.10 m, what is the waves
    frequency?
  • F 0.0033 Hz
  • G 33 Hz
  • H 330 Hz
  • J 3300 Hz

Use the formula chart!!! Velocity f ? OR 330
m/s f x 0.10 m
30
Transverse Waves
  • In Transverse Waves particles vibrate at right
    angles to the direction the wave travels.
  • Ex. E. M. Waves, waves on a slinky or rope coil,
    ocean waves

31
Waves - 2 Types
32
Longitudinal or Compress ional Waves
  • Vibrating particles move back and forth along the
    direction of the wave velocity
  • Parts consist of compressions and rarefactions
  • Ex. Sound Waves

33
Sound Waves are Compressional
  • Sound is produced when a compression is made.
  • It requires a producer and a medium to travel
    through.
  • The more elastic the object, the faster sound
    travels.

34
Sound acts like other waves
  • Echoes are reflected sound waves
  • Sonar uses echoes to judge distance to
    obstructions
  • Human hearing is 20-20,000 Hz, below 10 Hz is
    infrasonic, and above 20,000 Hz is ultrasonic.

35
Sound Waves move through matter not through empty
space.
  • 32 One tuning fork is struck and placed next to
    an identical fork. The two forks do not touch.
    The second tuning fork starts to vibrate because
    of
  • F interference
  • G the Doppler effect
  • H resonance
  • J standing 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.
36
Forces and Motion
  • Forces can create changes in motion
    (acceleration)
  • Deceleration is negative acceleration

37
Motion can be described simply
  • Motion is a change in an objects position
  • Average velocity (speed) is the change of
    position of an object over time

38
Velocity Graphs V distance time
  • Velocity (v) is the slope (rise over run) of a
    position (d) vs. time (t) graph

39
40 The diagram represents the total travel of a
teacher on a Saturday. Which part of the trip is
made at the greatest average speed? F Q G R H S J
T
How do we work this one? Calculate v d/t for
each segment.
40
Acceleration Graphs
  • Acceleration (a) is the slope of a velocity (v)
    vs. time (t) graph
  • Plotted on a distance vs. time graph,
    acceleration is an exponential curve

41
Acceleration is a change in an objects velocity
(speed or direction)
  • When an objects speed changes over time it is
    accelerating (or decelerating)
  • A vfinal vinitial
  • time
  • Units for acceleration m/s/s or m/s2

42
Forces
  • A pull or push (or lift) that can cause an
    object to start moving, stop moving or change
    direction.

43
Definition of a Force
  • A Force is a push or a pull

44
Balanced Force
  • A force that produces no change in an objects
    motion because it is balanced by an equal,
    opposite force.

45
4 The picture shows the position of a ball every
0.25 second on a photogram. Using a ruler,
determine the velocity of the ball.
  • F 3.5 cm/s
  • G 10.5 cm/s
  • H 14.0 cm/s
  • J 28.0 cm/s

46
Since the version of the test you took has the
picture smaller, we all got it wrong! The
answer was H.
Measure from the center of ball 1 to the center
of ball 2 and multiply by 4.
47
Unbalanced Forces
  • Are forces that results in an objects motion
    being changed.

48
Friction
  • A force that acts in a direction opposite to the
    motion of two surfaces in contact with each other.

49
Friction
  • Friction causes an object to slow down and stop.
  • Since the amount of energy stays constant, the
    energy becomes heat.

50
Newtons 1st Law of Motion
  • Object in motion stays in motion

51
Newtons 1st Law of Motion
  • And Objects at rest stay at rest

52
Newtons 1st Law of Motion
  • Until they are acted upon by unbalanced forces.

53
Inertia
  • Tendency for an object to stay at rest or moving
    in a straight line at a constant speed.
  • The mass (m measured in kg) of an object
    determines its inertia

54
Newtons 2nd Law of Motion
  • Force Mass X Acceleration
  • Fma
  • Weight (pull of gravity) is a
  • commonly measured force, calculated by Fmg, g
    is the acceleration due to gravity 9.8 m/s2

55
Newtons 2nd Law of Motion
  • The greater the mass of an object, the greater
    the force required to change its motion.

56
Newtons 2nd Law of Motion
  • The greater the acceleration of an object, the
    greater the force required to change its motion.

57
11 The frog leaps from its resting position at
the lakes bank onto a lily pad. If the frog has
a mass of 0.5 kg and the acceleration of the leap
is 3 m/s2, what is the force the frog exerts on
the lakes bank when leaping?
  • A 0.2 N
  • B 0.8 N
  • C 1.5 N
  • D 6.0 N

Formula chart says Fma, m is mass in kg, a is
acceleration in m/s2. So, .5 kg x 3 m/s2 1.5 N
58
Newtons 3rd Law of Motion
  • For every action force there is an equal and
    opposite reaction force.

59
Newtons 3rd Law of Motion
  • All forces come in action-reaction pairs
  • Ex feet push backward on floor, the floor pushes
    forward on feet

60
27 A ball moving at 30 m/s has a momentum of 15
kgm/s. The mass of the ball is
  • A 45 kg
  • B 15 kg
  • C 2.0 kg
  • D 0.5 kg

Formula Page says that Momentum Mass x Velocity
So 15 kg.m/s M x 30 m/s solving for M it
is
61
Work
  • Work using a force
  • for a distance
  • W F x d
  • The work done by forces on an object changes in
    energy for that object.
  • Work and Energy are measured in Joules
  • 1 Joule1 Newton meter

62
  • 42 How much work is performed when a 50 kg crate
    is pushed 15 m with a force of 20 N?
  • F 300 J
  • G 750 J
  • H 1,000 J
  • J 15,000 J

Use the formula Work Force x distance Force
of 20 N x 15 meters 300 Joules Answer
63
Why use a machine?
  • In an ideal (perfect) machine the work put into
    the machine (Win) the work put out by that
    machine (Wout)

64
Machines make work easier
  • The ideal mechanical advantage of a machine (IMA)
    of a machine is the number of times the output
    force is larger than the input force IMAFout/Fin
  • A machine can only make this happen by moving the
    input force through a farther distance than the
    output force
  • Fin dinFout dout

65
  • 48 The diagram shows an electric motor lifting a
    6 N block a distance of 3 m. The total amount of
    electrical energy used by the motor is 30 J. How
    much energy does the motor convert to heat?
  • F 9 J
  • G 12 J
  • H 18 J
  • J 21 J

66
Work Input 30J done by the motor
Work Output Resistance Force x Resistance
Distance Workout 18J 6N x 3m
The difference is lost as heat due to friction,
which is 30J 18J 12J Answer G
67
Real Machines use Energy
  • No real machine is 100 efficient. i.e. none put
    out more work than is put in
  • Efficiency of a machine is work output/work input
    X 100
  • Eff Wout X 100
  • Win

68
Machines use power
  • Power the rate at which energy is used (work is
    done)
  • PWork/time
  • Power is measured in H.P. or watts
  • 1 watt 1 Joule
  • 1 sec

69
45 If a force of 100 newtons was exerted on an
object and no work was done, the object must have
  • A accelerated rapidly
  • B remained motionless
  • C decreased its velocity
  • D gained momentum

Work Force x Distance Work 0 Force 100
N so 0 J 100 N x d distance must be 0 It
did not move!
70
6 Types of simple machines
  • Some Simple Machines
  • Inclined planes
  • Screws
  • Pulleys
  • Wheel and axle
  • Levers
  • Wedge

71
Universal Law of Gravitation
  • All objects in the universe attract each other by
    the force of gravity

72
Universal Law of Gravitation
1) the mass of the object doing the pulling, and
  • Gravity varies depending on two factors

2) the distance from the center of that object
73
On Earth gravity 9.8 m/s/s
  • For every second that an object falls its speed
    increases by 9.8 m/s

74
Weight Mass (m) X acceleration due to gravity (g)
  • Weight Unit of mass kg
  • Unit of acceleration m/s/s
  • Unit of weight Newton
  • 1 Newton about ¼ pound
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