Download Kinetic Energy

TURBO TAKS
Week 6
Lesson 1: Body Systems
Lesson 2: Heat Transfer & Waves
Lesson 3: Energy & Electricity
Lesson 4: Motion, Forces, & Physics Equations
Lesson 1:
Body Systems
The Human Body must also
maintain homeostasis (a
balance). The organs of the
body work together in organ
systems to perform specific
functions.
Organ systems are often
connected and work
together to allow the body
to function.
Integumentary: Skin, hair, nails:
Protects, prevents infection,
temperature control
Skeletal Support and protection
of organs.
Muscular Uses bones as simple
machines to exert force on the
body to create movement.
Nervous Control system of the
body. Works with other
systems to maintain
homeostasis.
Endocrine Secretes hormones
that circulate in the blood
stream and tell other systems
what to do.
Reproductive: produces
gametes in ovaries and testis.
Circulatory: transports
oxygen and nutrients to
cells and removes wastes.
Respiratory Brings O2 to
circulatory system and removes
CO2 (gas exchange!).
Immune Fights infection
Helper T-cells and macrophages turn
on the immune response and start
attacking invaders.
Digestive: breaks down
food and absorbs
nutrients
Excretory Takes waste
from the blood stream for
removal from the body.
Lesson 2: Heat Transfer and
Waves
Heat Transfers
• Heat moves from hot to cold.
• Example: When you put your hand on a
lab table it feels cold because the heat in
your hand is leaving your body and
transferring down, into the table. Not the
other way around.
25oC
10oC
– Heat from the 25oC block is sinking into the
10oC block
– Heat does not rise, hot air rises.
Conduction
Conduction transfers from one substance to
another by direct contact of molecules.
THINK: Solids
Example: When you touch a hot stove!
slow transfer
5oC
25oC
metal
wood
25oC
fast transfer
5oC
Convection
Convection transfers heat through moving currents in
fluids (gases or liquids). Convection cannot occur in
solids, because solids can’t move.
• THINK: Liquids and Gases
Hot air rises
sunshine
wind
wind
warm
ground
Cold air is pulled in
from the sides
causing wind.
Much of the weather on earth
comes from convection currents.
The sun warms air at the surface
of the earth. Warm air rises,
causing winds. When the air
cools it falls back to the ground.
Much of the
weather on earth
comes from
convection
currents. The sun
warms air at the
surface of the
earth. Warm air
rises, causing
winds. When the
air cools it falls
back to the ground
cooler
liquid
falls
Hot liquids (and
gases) are less dense
and rise, causing
Hot
convection currents.
Liquid
These currents
Rises
transfer heat
cooler
throughout the
liquid
liquid (or gas).
falls
Heat Source
Radiation
Heat (thermal energy) in the form of
electromagnetic radiation from a light source.
All energy on earth comes
originally from the sun. Only
radiation can travel through the
vacuum of space to the earth.
Radiation
• Examples:
• The sun warming your face.
• Warmth you feel sitting
close to a campfire.
Radiation transfers
heat through
electromagnetic waves
—
pure thermal energy.
Lets Practice
CONVECTION
Name the type of heat transfer:
1. Boiling water in a pot.
2. Your feet burning on concrete in the Summer time.
CONDUCTION
3. McDonalds keeping french fries
warm under a heat lamp.
RADIATION
A
20ºC
4. Which letter represents
a possible heat transfer?
20ºC
B
D
30ºC
40ºC
C
D
(Always
hot
cold)
.
Waves
A wave is any disturbance that transmits
energy through matter or space
Types of Waves
1.
2.
Types of Waves
• 1. Compression/ Longitudinal wave
• Produced by moving a slinky spring back and
forth.
• Example: Sound
Types of Waves
• 2. Transverse Wave
• Produced by waving
a rope or other medium
up and down
• Example: Light wave, or a ripple in a pond
Parts of a Transverse Wave
Characteristics of All Waves
• Wavelength- distance from a point in a wave to
the next point on the next wave in the same phase
• Frequency- the number of times that a repeated
event occurs per second
• For sound, High pitch
= high frequency
• V=f λ
Short Wavelength = High
Frequency
Long Wavelength = Low
Frequency
(Velocity = frequency x wavelength)
Wave Properties
• Reflection
• When waves bounce
off a hard boundary.
• The sound waves are
bouncing off the tank.
(i.e.- mirror, echo)
• Refraction
• The bending of light as it passes from
one medium into another. (i.e.- lenses)
Wave Properties
• Diffraction
• Occurs when a wave bends
around a corner.
• Interference
• A wave
interaction that
occurs when
two or more
waves overlap.
Wave Properties
• Resonance
• Occurs when one object vibrates because of
another object’s vibrations.
• Common in tuning forks and other musical
instruments
• Example: Earhearing
• Body of guitar vibrates
because of it’s strings
vibration.
(Fast-forward to about 30 sec in.
Turn speakers to low volume.)
Lets Practice
• Answer with: Reflection, Refraction,
Diffraction, Interference, or Resonance.
2. Using a mirror 3. Water waves passing
1. Lenses
through an opening.
REFRACTION
4. When the
primary colors of
light combine to
form white light
INTERFERENCE
REFLECTION
5. When singing
near a piano, the
keys can start to
sound.
RESONANCE
DIFFRACTION
Lesson 3: Energy and
Electricity
(Can fastforward to
20
seconds)
Energy
• Energy is the ability to cause motion or forces; the
units of energy are joules (J).
Potential Energy
• 1. Gravitational Potential Energy (in Joules, J) is
stored energy, because an object is above the ground.
• More height = more Potential Energy. It has the potential
to cause motion and forces.
Potential
Energy
(in Joules)
Ep = mgh
mass (in kilograms)
height (in meters)
acceleration due to
gravity (9.8 m/s2 )
Potential energy equals
mass times gravity times height.
• Gravitational Potential Energy= mass x gravity x height
Potential Energy
• The acceleration due to gravity we
experience on Earth is 9.8 m/s2. In
space, gravity is 0 m/s2.
Don’t forget
to use the
given
constants and
formulas!
• Potential Energy Practice:
Ex: How much potential energy does a 4 kg object have that
is 5 meters off the ground?
m == 4 kg
m
hh == 5 m 2
gg == 10 m/s
EEpp == ?
Ep = mgh
Ep = (4)(10)(5)
= (40)(5)
= 200 Joules
Kinetic Energy
• Kinetic Energy (in Joules, J) is the energy of
motion. Moving objects have kinetic energy.
• Kinetic Energy= ½ mass x velocity2
mass (in
Kinetic
kilograms)
Energy
2
E
=
(½)mv
k
(in
velocity (in m/s)
Joules) Kinetic energy equals one-half
Times mass times velocity squared.
• Mass is measured in kilograms (kg) and velocity is
measured in meters/second (m/s).
Energy Transfers
• Energy can be transferred from one type to another.
• Work (in Joules, J) is
• Power (in Watts, W)
how forces change
energy.
is how fast work is
done.
• Work=Force x Distance
• Power = Work
Time
Work
(in
Joules)
W = Fd
Force (in
Newtons)
Distance (in
meters)
Power
(in
Watts)
P = W/T
Work (in
Joules)
Time (in
seconds)
Efficiency
• Efficiency is the percentage of energy retained (not
lost) in an energy transfer.
Energy gained by
the object (in J)
Efficiency
(in %)
Wout
Eff 
x100
Win
Energy you tried to give
the object (in J)
Efficiency Calculation
Work In:
How much energy you tried to
give to the object thru an energy
transfer or work.
Here work is done on
the object, pulling it
up the ramp. This is
the total energy that
you tried to give the
object.
Work put
in 240 J.
Win=Fd=
30(8)=240 J
Work Out:
How much energy is
actually gained by the object
(how much it got out).
The object only
got out 200 J.
After
10
kg
2m
Wout=Epgained
Wout
Eff

x100
=mgh
Win
=10(9.8)2
Ep
=98(2)
Eff  x100
= 196J
W
196J
200

x100
240 J
100
 .82
.83 xx 100
=82%
= 83%
Types of Energy
• Thermal Energy—Heat
energy. A product of most
other forms of energy.
• Mechanical Energy—Any
kind of Kinetic (moving) or
Potential (height) Energy.
• Electrical Energy—Energy of
moving electrons: lightening,
electricity.
• Radiant Energy—Light energy
from light bulbs or the sun
(renewable solar energy).
• Chemical Energy—Stored in • Nuclear Energy—Energy from
chemical bonds. Includes
energy in food, plants, and
batteries (produce electricity
by combining chemicals).
nuclear reactions (radiation):
makes huge amounts of energy,
but also long-term, radioactive
waste like power plants.
Lets Practice
Match with the terms to the right:
WORD BANK
1. The units for energy.
a) Kinetic Energy
2. The ability to create forces or motion.
b)Potential Energy
3. Energy because of an object’s motion.
c)Energy
4. Energy because of an object’s position above
the ground due to gravity.
d)Height
5. Vertical distance above the ground.
e)Joules
Electricity
• Moving of electrons through conductors.
The path must be closed, or electrons
cannot move.
Electrical Circuits
• Series Circuit
• Provides a single
conducting pathway
without junctions.
• Parallel Circuit
• When two or more components of
a circuit are connected across
junctions, providing separate
pathways for the current.
Which type of circuit would you rather have for your Christmas lights?
Parallel, so that if one light burns out, the current can still reach
the other bulbs.
Assuming the chart contains all energy transformations in the
Earth system, how much solar radiation
Subtract all the energy
goes toward evaporating water?
expenditures from the
F
40,000 terajoules
total amount reaching
G
92,410 terajoules
Earth.
H
121,410 terajoules
J
133,410 terajoules 173,410 – 52,000- 81,000 – 370 – 40 = 40,000
Lesson 4: Motion, Forces, and
Physics Equations
Speed and Velocity
• Speed is the distance an object travels per
second.
• Velocity includes the speed of an object and
the direction of its motion.
Distance travelled
(in meters)
Time
(in seconds)
Speed
d
v
=
(in
t
meter/sec)
Speed equals the distanced traveled
divided by the time it took to move that
distance.
d
s
t
• They share a formula on your equation sheet.
Measuring Speed
To measure speed you must determine the
distance traveled and the elapsed time.
Initial Position
Distance Traveled
Final Position
25 m
0:00.0
Elapsed Time
5 sec
0:05.0
D
25m
S 

 5m/s
T
5sec
a=
Acceleration
Acceleration is how fast you change velocity OR how much the
velocity changed in a certain amount of time.
An object accelerates when it changes speed OR changes
direction!
Acceleration
(in m/s2)
ΔV
a=
ΔT
Change of
Velocity
(in meters/sec)
Acceleration equal change of velocity
divided by change of time.
V  V final  Vinitial , so, a 
Change of
Time
(in seconds)
V final  Vinitial
T
If acceleration is unknown use acceleration due to
gravity out of the constants box on the formula chart!
Solving for Acceleration
1. Calculate initial velocity
2. Calculate final velocity
Measure ΔT
(Time it took to
Accelerate)
Measure Vi
(Initial Velocity)
0.0
4m
3. Determine the change in time.
4. Plug into acceleration equation.
Measure Vf
(Final Velocity)
Accelerates for
2 seconds
1.0
D
4m
Vi 

T
1sec
Vinitial  4m/s
So ΔT = 2 sec
a
V f  Vi
84

2
T
4
Vinitial   2m/s 2
2
8m
3.0
4.0
D
8m

T
1sec
V final  8m/s
Vf 
MOMENTUM
• Momentum is how hard it is to stop something and is a
product of an object’s mass and its velocity. Momentum
is increased if either the mass or velocity is increased.
Mass (in kg)
Momentum
(in kgm/sec)
p = mv
Momentum equals
mass times velocity.
Velocity (in m/sec)
Momentum
Click to play
The bullet has a smaller
mass and a larger velocity.
The gun has a larger mass
and a smaller velocity.
However, since the
system started with a net
momentum of zero, the
momentums of the objects
afterwards must be equal
and opposite to cancel
each other out,
or = 0.
Forces
• A force is a push or pull that one body exerts
on another. Force is measured in Newtons (N).
• Forces can add and subtract.
Total Net Force
= +65 -15
= 50 N
10 kg
15 N
65 N
Left is negative. Right is positive.
Newton’s Laws of Motion:
1.
An object in motion will stay
in motion unless a force acts
upon it. (Law of Inertia). If
an object is at rest, it will
stay at rest until acted upon.
*Why we need seatbelts.
2.
Force = mass x acceleration
*Why a bowling ball does not
go as fast as a ping pong ball
when the same force is
applied.
3.
For every action there is an
equal and opposite reaction.
*Why a rocket goes up when
gasses push down.
Inertia
Inertia is the tendency to not change
motion, and is dependent only on the
object’s mass (measured in kilograms).
- Newton’s First Law.
Object’s with more
mass have more inertia
and are harder to push.
Object’s with less
mass have less inertia
and are easier to push.
Frequent Equations from the Formula Sheet
Solving Physics Problems:
1. Identify what is being asked and underline
or highlight it.
2. Find the appropriate formula and write it
down in your test booklet.
3. Plug in the known information
(WRITE IT OUT).
4. Solve for the unknown.
Lets Practice the Steps Together…
• What is the approximate difference in
gravitational potential energy of a 2kg
object 3m off the ground and a 2kg object
1m off the ground?
•
•
•
•
F) 19J
G) 39 J
H) 59 J
J) 79 J
First Situation
PE=mgh
PE=(2)(9.8)(3)
PE= 58.8 J
Second Situation
PE=mgh
PE=(2)(9.8)(1)
PE= 19.6 J
Difference Between=
58.8 – 19.6 = 39.2 J
or approximately 39J = G
The illustration above shows a student about to throw a ball while
standing on a skateboard. Which illustration below correctly shows the
skateboard’s direction of motion after the student releases the ball?
A
B
C
D
• A cyclist moves at a constant speed of 5
m/s. If the cyclist does not accelerate during
the next 20 seconds, he will travel —
•
•
•
•
A0m
B4m
C 50 m
D 100 m
They are asking for distance
and giving us speed and time.
S=d/t
5=d/20
(Multiply by 20 on each
side of the equal sign.)
20 x 5= 100m = D
• How much work is performed when a 50 kg
crate is pushed 15 m with a force of 20 N?
•
•
•
•
Watch out for extra information!
F 300 J
G 750 J
H 1,000 J
J 15,000 J
W=Fd
W= (20)(15)
W= 300 J = F
Levers
Which lever arrangement requires the least
effort force to raise a 500 N resistance?
A mechanic used a hydraulic lift to raise a
12,054 N car 1.89 m above the floor of a
garage. It took 4.75 s to raise the car. What
was the power output of the lift?
•
•
•
•
A) 489 W
B) 1815 W
C) 4796 W
D) 30,294 W
This is a two part calculation.
You’re looking for Power, but must have
work before you can solve (P=w/t)
1. Calculate work: 2. Calculate power:
w=fd
P=w/t
w=(12054)(1.89)
p=(22,782.06)
w=22,782.06
(4.75)
P=4796.22 W
We know it’s a force because it’s
measured in Newtons!
• A ball moving at 30 m/s has a momentum
of 15 kg·m/s. The mass of the ball is —
•
•
•
•
A 45 kg
B 15 kg
C 2.0 kg
D 0.5 kg
Momentum = mass x velocity
P=mv
15=m(30)
Divide by thirty on both sides.
15/30= 0.5 kg = D