Title: TAKS Objective 5
1TAKS Objective 5
- Motion , Forces
- and Energy
2Energy
- Is defined as the Ability to do Work
- Energy has Two
- Types
Kinetic (Energy of Motion) and Potential (Stored
Energy)
3Kinetic Energy
- KE ½ m v 2
- Ex A moving car has the ability to do work on
the light pole if it hits it.
4Potential Energy 2 possibilities
- Gravitational PE -Object lifted to some height
- Elastic PE - A stretched or compressed object
)(springs
5Gravitational 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
6Use 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
7Law 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.
8Example 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
9Energy 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
10Electrical 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).
11Circuits 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)
12Circuits 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?
It is the only switch in series to both the
battery and light.
14USE 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
15Thermal 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
16Heat- 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. . .
173. 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
18Heat 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
192 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.
2050 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
21Nuclear 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
22Nuclear 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
23Radiant 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
24Electromagnetic 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
25The 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
26Waves - 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
27All 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
28Velocity 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
29And 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
30Transverse 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
31Waves - 2 Types
32Longitudinal 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
33Sound 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.
34Sound 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.
35Sound 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.
36Forces and Motion
- Forces can create changes in motion
(acceleration) - Deceleration is negative acceleration
37Motion 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
38Velocity Graphs V distance time
- Velocity (v) is the slope (rise over run) of a
position (d) vs. time (t) graph
3940 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.
40Acceleration 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
41Acceleration 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
42Forces
- A pull or push (or lift) that can cause an
object to start moving, stop moving or change
direction.
43Definition of a Force
- A Force is a push or a pull
44Balanced Force
- A force that produces no change in an objects
motion because it is balanced by an equal,
opposite force.
454 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
46Since 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.
47Unbalanced Forces
- Are forces that results in an objects motion
being changed.
48Friction
- A force that acts in a direction opposite to the
motion of two surfaces in contact with each other.
49Friction
- Friction causes an object to slow down and stop.
- Since the amount of energy stays constant, the
energy becomes heat.
50Newtons 1st Law of Motion
- Object in motion stays in motion
51Newtons 1st Law of Motion
- And Objects at rest stay at rest
52Newtons 1st Law of Motion
- Until they are acted upon by unbalanced forces.
53Inertia
- 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
54Newtons 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
55Newtons 2nd Law of Motion
- The greater the mass of an object, the greater
the force required to change its motion.
56Newtons 2nd Law of Motion
- The greater the acceleration of an object, the
greater the force required to change its motion.
5711 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
58Newtons 3rd Law of Motion
- For every action force there is an equal and
opposite reaction force.
59Newtons 3rd Law of Motion
- All forces come in action-reaction pairs
- Ex feet push backward on floor, the floor pushes
forward on feet
6027 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
61Work
- 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
63Why use a machine?
- In an ideal (perfect) machine the work put into
the machine (Win) the work put out by that
machine (Wout)
64Machines 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
66Work 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
67Real 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
68Machines 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
6945 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!
706 Types of simple machines
- Some Simple Machines
- Inclined planes
- Screws
- Pulleys
- Wheel and axle
- Levers
- Wedge
71Universal Law of Gravitation
- All objects in the universe attract each other by
the force of gravity
72Universal 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
73On Earth gravity 9.8 m/s/s
- For every second that an object falls its speed
increases by 9.8 m/s
74Weight 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