Transcript TAKS Objective V with background info edited

Objective 5
Motion, Forces, and
Energy
IPC 4A – Calculate speed,
momentum, acceleration,
work, and power in
systems such as in the
human body, moving
toys, and machines.
Common measurements and
symbols
Measurement
Symbol
Typical Units on TAKS
speed or velocity
v
m/s
momentum
p
kg.m/s
acceleration
a
m/s2
Work
W
J
Power
p
W
Force
F
N
Time
t
s
Mass
m
kg
E, KE or PE
J
Energy
Using the formula chart
1. Circle what you are asked to find
2. Underline given facts with numbers and units
and write the symbol above it.
3. Identify the formula(s) you will use from the
formula chart
4. Rearrange the formula for what you’re asked to
find.
5. Put in numbers for symbols and solve.
6. Check that you answered the question asked.
Rearranging formulas
When a formula is not solved for the variable
you are trying to find, then you need to
rearrange it until your variable is alone on
one side of the equation.
Rearranging formulas
Example, the speed formula is:
If you are given speed and time and want to
find distance, what would the formula be?
Rearranging formulas
Here, you divided d by t. To
move t to the other side, do
the opposite, multiply by it.
t cancels on the right side
And you are left with the
formula for d.
Speed and Velocity
How fast an object is traveling.
Velocity has direction, speed does not.
Acceleration
The change in velocity
If an object is moving at a constant speed,
acceleration = 0
Negative acceleration (deceleration) means
the object is slowing down.
Work
Using force to move an object a certain
distance.
If there is no movement, there is no work
done. If distance = 0, work = 0
Does not depend on the time it takes to do
the work
If Distance = 0,
then
Work = 0.
Power
The rate at which work is done.
More power means the same work can be
done faster.
How could this person increase his
power?
What is the power of this motor?
Power = Work/time
Time = 5 s
We must find the work first!
Work = Force x distance
= 10 N x 2m = 20 J
Power = Work/time
= 20J/5s
=4 Watts
Momentum
The product of an object’s mass and
velocity.
Can be thought of as how difficult it is to stop
a moving object.
A stopped object has zero momentum.
Conservation of Momentum
In collisions, total momentum does not
change. The momentum of the objects
(together) before the collision is the same
as the momentum of the objects (together)
after the collision.
Distance vs. Time graphs
In a distance vs. time graph, the slope of
the line is the speed of the object.
If you have a horizontal line, the object is
stopped.
Distance (Miles)
25
20
No speed = stopped
15
10
5
0
0
5
Tim e (hours)
10
120
100
100
Distance (Miles)
Distance (Miles)
120
80
60
40
80
60
40
20
20
0
0
0
5
10
Tim e (hours)
Constant speed away from a point
0
5
10
Tim e (hours)
Constant speed toward a point
100
Distance (Miles)
Distance (Miles)
200
150
100
50
80
60
40
20
0
0
0
0
5
10
5
10
Tim e (hours)
Tim e (hours)
The line gets steeper – speeding up
The line gets less steep – slowing down
Velocity vs. Time Graphs
In a velocity vs. time graph, the slope of
the line is the acceleration of the object.
In this type of graph, a horizontal line
means that the object is moving at a
constant speed.
Two ice hockey players are skating directly at
each other. The first has a mass of 87 kg and is
skating at a constant speed of 2.6 m/s. The
second skater has a mass of 78 kg. How fast
must the second skater be skating in order to
have a momentum similar to the first skater?
A 2.3 m/s
B 2.9 m/s
C 3.4 m/s
D 5.2 m/s
How much force is needed to accelerate a
1,300 kg car at a rate of 1.5 m/s2?
F 867 N
G 1,950 N
H 8,493 N
J 16,562 N
An ant crawled from Point A to Point B in
4.0 seconds. To the nearest tenth, what
was the ant’s speed in centimeters per
second?
Assume the ant traveled 5.6 cm.
1.4 cm/s
The diagram represents the total travel of a
teacher on a Saturday. Which part of the trip is
made at the greatest average speed?
FQ
GR
HS
JT
A car traveled 150 km in 2.5 hours. What
was its average speed in km per hour?
Record and bubble in your answer on the
answer document.
60 km/h
Which bike rider has the greatest
momentum?
A A 40 kg person riding at 45 km/h
B A 50 kg person riding at 35 km/h
C A 60 kg person riding at 25 km/h
D A 70 kg person riding at 15 km/h
IPC 4B – Investigate and
describe [applications of]
Newton’s laws such as in
vehicle restraints, sports
activities, geological
processes, and satellite
orbits.
Forces
Force can be defined as a push or a pull.
Forces can be balanced, which mean they
are equal and opposite with no change in
direction. If the forces on an object are
balanced, it will either remain at rest or it
will move at a constant speed in a straight
line.
Unbalanced forces cause an
object to accelerate (speed up,
slow down or change direction) in
the direction of the largest force.
Friction is a force that acts in the opposite
direction to the motion of a moving object.
Newton’s Laws
Newton’s First Law: An object at rest will
remain at rest and an object in motion will
remain in motion at a constant velocity
unless acted upon by an unbalanced
force.
The Law of Inertia.
Orbits and Inertia
Newton’s Second Law:
Force = mass x acceleration
For a constant force, if mass increases
acceleration decreases
For a constant mass, if force increases,
acceleration increases
The force on the ball and the force on the cannon are equal
(See 3rd Law).
F = ma
The ball’s mass is lower, so its acceleration is higher.
The cannon’s mass is greater, so its acceleration is lower.
Newton’s Third Law: For
every action force, there is
an equal and opposite
reaction force.
In the event of an accident, air bags and seat
belts may help reduce injury to a passenger by
decreasing the force that stops the passenger’s
motion. The force is reduced because the seat
belts or air bags decrease the —
A mass of the passenger
B acceleration of the passenger
C reaction time of the driver
D speed of the vehicle
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?
The table shows times required
for the same toy car to travel
10 m across an identical
section of a floor after it is
pushed. The difference in times
was probably caused by
differences in —
A force exerted
B surface friction
C air resistance
D car mass
IPC 5A – Demonstrate
wave types and their
characteristics through a
variety of activities such
as modeling with ropes
and coils, activating
tuning forks, and
interpreting data on
seismic waves.
Types of Waves
1. Transverse
2. Longitudinal
(compression)
Parts of a Wave
Calculating Wave Speed
Velocity of a wave =
Wavelength • Frequency
Measured in Hz
A surfer wishing to ride a big wave is most
interested in a wave’s —
A rarefaction
B compression
C amplitude
D wavelength
At 0°C 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 wave’s frequency?
F 0.0033 Hz
G 33 Hz
H 330 Hz
J 3300 Hz
Which illustration
best demonstrates
compression
waves?
IPC 6A – Describe the law
of conservation of
energy.
Energy
energy- the ability to do work
unit: joule (J)
Types of Energy:

kinetic energy- the energy of motion
the faster an object moves, the more kinetic energy it has
depends on both mass & velocity
KE = ½ (mv2)

potential energy- energy of position
stored energy that the object was given when work was done
on it – a ball rolled to the top of a hill
it has the ability to give that work back—a stretched rubber
band
GPE is potential energy due to gravity. GPE = mgh
(remember g = 9.8m/s2)
law of conservation of energyenergy may neither be created nor
destroyed
it can only be transformed into various forms—
from kinetic to potential, from chemical to
mechanical
the total energy in the system is constant
Where is the PE greatest?
Where is the PE least?
Where is the KE greatest?
Where is the roller coaster moving
the fastest?
Energy conversions
Types of Energy
mechanical energy- energy of motion—hitting a ball,
walking, blood flowing through your vessels
heat energy- internal motion of atoms; usually results from
friction—causes phase & temperature changes
chemical energy- energy that exists in the bonds that hold
atoms together—starting a fire, burning fuel, digesting
food
nuclear energy- energy associated with the nucleus of an
atom; produces the sun’s energy due to nuclear fusion-hydrogen changes to helium
electromagnetic energy- energy associated with moving
charges—microwaves, X-rays
Energy conversions
Powerful Plankton
The U.S. Naval Research Laboratory has created an experimental
marine fuel cell that could produce enough electricity to power
ocean-monitoring devices. This fuel cell runs on seawater and
sediment, with the help of plankton. Some plankton on the surface of
ocean sediments use dissolved oxygen to break down organic
matter, releasing energy; this is an aerobic process. The plankton in
the deeper sediments break down organic matter without using
oxygen; this is an anaerobic process. These two processes create a
difference in voltage between the surface of the sediment and the
sediment farther down in the seabed. The voltage difference can be
used to produce electricity-up to 5.0 x 10–2 watts of power. Energy
supplied by this type of fuel cell can be obtained as long as there is
organic matter in the sediment. Fuel cells powered by plankton from
the seabed can be used to operate instruments that monitor ocean
currents and water temperature. These fuel cells get their energy by
converting —
F chemical energy to electrical energy
G electrical energy to mechanical energy
H hydroelectric energy to geothermal energy
J mechanical energy to chemical energy
IPC 6B – Investigate and
demonstrate the
movement of heat
through solids, liquids,
and gases by convection,
conduction and radiation.
Kinetic theory



all matter is made up of atoms & molecules
that act like tiny particles
these tiny particles are always in motion; the
higher the temperature, the faster the
particles move
at the same temperature, more massive
(heavier) particles move slower than less
massive (lighter) particles
heat- a form of energy caused by the
internal motion of molecules
cold- the absence of heat
heat transfer- the movement of heat from
a warmer object to a cooler one
3 methods of heat transfer
1. conduction- heat is transferred through a
substance, or by the direct contact of
molecules
takes place in solids, liquids, & gases, but does
best in solids
one particle must contact another for this to occur.
In solids, the particles are close to each other,
which makes contact easier.
Conductors vs. Insulators
conductors- substances that
conduct heat better & more rapidly
than others (silver, copper, iron)
insulators- substances that do not
conduct heat easily (glass, plastic,
wood, rubber)—wearing several
layers of clothing in extremely cold
weather
3 Methods of Heat Transfer
2. convection- takes place in liquids &
gases as up-and-down movements called
convection currents.
Does not occur in solids
3 Methods of Heat Transfer
3. radiation- heat energy transfer through
empty space
This is how the sun heats the earth
Which method is shown?
Which method is shown?
Mud at the bottom of a fishpond has a
temperature of 15°C. After a week of colder air
temperatures, the mud temperature drops to
12°C. Which of the following methods of heat
transfer is most responsible for the change in the
mud temperature?
A Water convection
B Air conduction
C Water reflection
D Ground radiation
The primary way liquids and gases
transmit heat is by the process of —
A reflection
B conduction
C radiation
D convection
A man who was sleeping wakes up because he
hears the smoke alarm go off in his house.
Before opening the bedroom door, the man feels
the door to see whether it is warm. He is
assuming that heat would be transferred through
the door by —
A conduction
B convection
C radiation
D compression
IPC 6F – Investigate and
compare series and
parallel circuits.
Electric Circuits
IPC 6F – Investigate and compare series and
parallel circuits. (10th grade only)
Circuits
To have an electric circuit, you need:
a closed conducting path which extends
from the positive terminal to the negative
terminal.
An energy source, such as a battery.
Will the bulb light?
Will the bulb light?
Closed
loop!
Series circuit
each device is connected in a manner
such that there is only one pathway by
which charge can traverse the external
circuit.
What happens if the first
light bulb burns out?
Parallel Circuits
In a parallel circuit, each device is placed
in its own separate branch. The presence
of branch lines means that there are
multiple pathways by which charge can
flow through the external circuit.
What happens if the first
light bulb burns out?
Circuits Math
Voltage (Volts)
Current (Amps)
Resistance (Ώ)
Which switch, if
opened, will cause the
lightbulb to stop
glowing?
FQ
GR
HS
JT
What is the current in a copper wire that
has a resistance of 2 ohms and is
connected to a 9-volt electrical source?
F 0.22 amp
G 4.5 amps
H 11.0 amps
J 18.0 amps
How much current is flowing through this circuit?
A 0.32 A
B 3.1 A
C 4.0 A
D 12.5 A
Which circuit is built so
that if one lightbulb goes
out, the other three
lightbulbs will continue
to glow?