Download 7th Grade 2nd Sixth Weeks Review

STAAR Review
A quick Glance.
Are you ready for the big GAME
Overview
• Forces and Motion
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Formula Chart Review
Energy Transformations
Potential and Kinetic Energy
Balanced and Unbalanced Forces
Graphing Motion
Work and Simple Machines
Waves
Energy vs. Matter
Everything on Earth is either energy or matter
• Energy has no
mass or weight
• Energy does not
take up space
• Energy is NOT
matter
• Matter has mass
and weight
• Matter takes up
space
• Matter is NOT
energy
Energy is the ability to do work
FORMS OF ENERGY
• Thermal- the total potential and kinetic energy based on the
vibrations and movements of atoms and molecules. Examplesfriction, changes in state of matter
• Chemical Energy- is stored in chemical bonds. Energy is
released when chemicals are broken apart. New molecules are
then formed. Example- digestion, burning match, photosynthesis
FORMS OF ENERGY
• Mechanical Energy- energy of motionmoves objects. Examples- water in a
waterfall, wind, moving vehicles
• Radiant- Energy carried by light. All life
on earth is dependent on radiant energy
from the sun. Examples- radio waves
(AM, FM, TV), microwaves, X-rays, and
plant growth.
• Electrical- energy of electrons moving
along a path (electrical current).
Examples- power lines carry electricity,
electric motors are driven by
electromagnetic energy
• Nuclear Energy stored in the nucleus of
an atom. Energy is released through the
splitting of an atom. Examples- fission, or
fusion in the production of sunlight
Energy Transformations
• The most common • During energy
energy conversion
transformations,
involves the
energy is often
changing of
released as light,
potential energy
heat, or sound.
into kinetic energy • Law of
or vice-versa.
Conservation of
Examples:
Energy – Energy
• Ball thrown in the air can be changed into
many
forms;
it
is
• Roller coaster
never lost.
Energy conversions
Clock
Battery
Light bulb
Blender
Solar Panel
Photosynthesis
CD Player
Dam
Windmill
Electrical
Chemical
Electrical
Electrical
Sunlight
Sunlight
Electrical
Mechanical
Mechanical
Light/sound
Electrical
Light/thermal
Mechanical
Electrical
Chemical
Mechanical
Electrical
Electrical
Energy Transformations Checkpoint 4.1
Diesel fuel is used in the engines of the machines and
trucks at a quarry. Which of these is the main energy
transformation as the fuel is used by the engines?
F
G
H
J
Electrical energy is converted to heat energy.
Heat energy is converted to potential energy.
Electrical energy is converted to kinetic energy.
Chemical energy is converted to kinetic energy.
Potential and Kinetic Energy
• Potential- stored
energy, due to an
objects position
• Kinetic- energy of
motion based on
the mass and
speed of the
moving object
POTENTIAL ENERGY
• Potential Energy (PE) is
energy an object has
because of its position.
• Potential energy
(PE)=the mass of an
object (x) gravity (x) it’s
height.
• PE is stored energy.
KINETIC ENERGY
• Kinetic energy (KE) is
the energy of motion.
• Only a moving object
has kinetic energy
• Amount of energy
depends on speed
and mass.
Kinetic Energy
• Mass- An object with
more mass has more
kinetic energy than an
object with less mass if
both are traveling at
the same speed.
• Speed- The faster an
object moves the
greater its kinetic
energy.
Roller Coaster
• The cars of a roller
coaster have the greatest
potential energy at the
top of the first hill. As they
start their descent, the
cars lose potential energy
and they gain kinetic
energy - the energy of
motion. Throughout the
ride, each time the train
loses height, it gains
speed as potential energy
is transformed into kinetic
energy. Likewise, each
time it gains height, it
loses speed as kinetic
energy is transformed into
potential energy.
Energy Transformations
Wind has
kinetic energy
which can be
transformed
into other forms
of energy.
Hydropower
depends on the
transformation
of potential
energy to
kinetic energy.
The kinetic
energy of the
fast-moving
water turns
turbines, which
drive
generators that
produce
electricity.
The energy in
fossil fuels
(coal, oil, gas) is
chemical
potential energy.
Fossil fuels come
from decayed
living matter that
has stored
energy in its
chemical bonds.
Potential and Kinetic Energy
Checkpoint 4.2
The diagram above shows a barrel moving toward a waterfall. The barrel will
have the greatest potential energy at which of these locations?
A
B
C
D
W
X
Y
Z
Motion
• Frame of Reference -Object or point from
which motion is determined
• Motion is a change
in position relative to
a frame of reference
What is motion?
• If you are standing in one place, and your friend
walks by you, are you moving relative to your
friend?
– Is your friend moving relative to you?
– Is either of you moving relative to the earth?
Speed
• Speed = Distance ÷ Time
S= D
T
Example: A car travels 300km in 6 hours.
What is the speed of the car?
Answer:
• Speed = distance ÷ time
• Speed = 300km ÷ 6 hours
• Speed = 50km/hr
Distance-time graphs
• On your paper, graph the following:
–
D (m)
0
5
10
15
T (sec)
0
7
14
21
Distance-time graphs
Is your graph a straight line?
• A distance-time graph which is a
straight line indicates constant
speed.
• In constant speed, the object
does not speed up or slow down.
The acceleration is zero.
Graph the following on a distancetime graph:
•
D (m)
0
5
20
45
80
125
T (s)
0
1
2
3
4
5
Does your graph curve?
• A graph that
curves on a
distancetime graph
shows that
the object is
accelerating.
0 1 2 3 4 5
Distance-time graphs
• Describe the motion of the object as shown
in the graph.
•From 0-8 sec, constant speed:
(25 m/sec);
•From 8-12 sec, no motion;
•From 12-16 sec, acceleration;
•From 16-20 sec, constant speed
Speed-time graphs
• Using the distance-time graph from the
last frame, draw a speed time graph.
Average Speed (m/s)
Time (sec)
25
0 to 8
0
8 to 12
37.5
12 to 20
What does your graph look like?
• Constant speed will be a
horizontal line on a speed time
graph.
• If the speed decreases, the line
will slant down.
• If the speed increases, the line
will slant up.
What do the following speed-time
graphs depict?
Graphing Motion Checkpoint 4.3
•
1
The graph shows the movement of a car over time. What is the car’s
average speed?
F
G
H
J
10 kilometers per hour
15 kilometers per hour
30 kilometers per hour
60 kilometers per hour
Force
• A force is a push or a
pull.
• A force always acts in
a certain direction.
– When you push on a
door, the force is in the
direction of the push.
– When you pull on a
doorknob, the force is
in the direction of the
pull.
Forces in Living Systems
• The body uses force;
– To move body parts, when
you bend your arm your one
muscle contracts to exert
force while the other muscle
relaxes.
– During breathing muscles
contract to move air in and
out of the lungs.
– The heart also contracts to
pump blood through the
blood vessels, carrying
oxygen
• Fish exert force to swim by
pushing against the water.
• Plant Seedlings exert force
on the surrounding soil to
emerge from the ground.
Balanced Forces
• To describe a force, you must know two
things-the size of the force and the
direction of the force.
– For example, think about two teams in a tug
of war.
– Each team pulls with equal force in opposite
directions.
– Neither team can make the other move.
Balanced Forces (2)
• Forces that are
equal in size and
opposite in
direction are called
balanced forces.
Unbalanced Forces
• Unbalanced forces cause a change in the
motion of an object.
• The forces acting on the rope are no longer
balanced.
Forces and Motion
• Unbalanced forces can change the motion of an
object in two ways.
– When unbalanced forces act on an object at rest, the
object will move.
– When unbalanced forces act on a moving object, the
motion of the object will change. The object may speed
up, slow down, stop moving, or change direction.
Solving for Force
• An unbalanced force acting on an object
equals the object’s mass times its
acceleration.
F=mxa
Force is measured in Newtons.
Acceleration: a measurement of how quickly an object is changing speed.
Friction
• Flying baseballs slow down and eventually
stop because of the force of gravity.
• Cars and bikes eventually slow down and
stop because of the force of friction.
• Types of friction:
•
a. Static (usually the greatest)
•
b. Sliding
•
c. Rolling (usually the least)
Balanced and Unbalanced Forces
Checkpoint 4.4
If a force is applied for 15
seconds, in which situation
will the box be moved the
greatest distance?
WORK
• Work is done when a force causes an
object to move in the direction that the
force is applied.
• The formula for work is: W = F X D
Formula
Chart
• If there is no movement, there is no work.
The Unit of Work is the Joule
Force x Distance = Work
–1 Newton x 1 meter = 1 Newton meter
–1 Newton meter = 1 Joule
Example 1:
• A high jumper weighs 700 newtons.
What work does the jumper perform
in jumping over a bar 2.0 meters
Use your
high?
Formula Chart
• Answer: W = F x d
• W = 700N x 2.0 m
•
= 1400 nm
•
= 1400 Joules
Work and Simple Machines
Two things must happen for work to be done.
• A force must be applied to an object
• The object must move in the same direction
as the force.
Simple machines are used to make work easier.
What is a Simple Machine?
• Simple machines make
work easier
– Reduce input force but
work remains the
same.
– Change the size and
direction of force.
– Do work with one
movement
• A simple machine has
few or no moving parts.
Wheels and Axles
• The wheel and axle
are a simple machine
• The axle is a rod that
goes through the
wheel which allows
the wheel to turn
• Gears are a form of
wheels and axles
Pulleys
• Pulleys are wheels
and axles with a
groove around the
outside
• A pulley needs a
rope, chain or belt
around the groove to
make it do work
Inclined Planes
• An inclined plane is a
flat surface that is
higher on one end
• Inclined planes make
the work of moving
things easier
Wedges
• Two inclined planes
joined back to
back.
• Wedges are used
to split things.
Screws
• A screw is an
inclined plane
wrapped around a
shaft or cylinder.
• The inclined plane
allows the screw to
move itself when
rotated.
Levers-First Class
• In a first class lever
the fulcrum is in the
middle and the load
and effort is on either
side
• Think of a see-saw
Note: The fulcrum is a pivot
point that changes the
direction of the force.
Moving the fulcrum changes
the distance each arm moves
under a force.
Levers-Second Class
• In a second class
lever the fulcrum is at
the end, with the load
in the middle
• Think of a
wheelbarrow
Levers-Third Class
• In a third class lever
the fulcrum is again at
the end, but the effort
is in the middle
• Think of a pair of
tweezers or fishing
pole
Simple Machines Checkpoint 4.5
The girl in the picture above is using a lever to lift a
heavy box. Using the lever makes the girl’s task easier
by —
A reducing the input force
B reducing the box’s mass
C increasing the amount of work done
D increasing the distance the box is lifted
Waves
• By moving a rope regularly up and down,
a traveling or periodic wave is produced.
Waves transfer energy from one place to
by vibrating something up and down, or
back and forth.
A transverse wave is a wave in which
the particles of the medium are
displaced in a direction perpendicular
to the direction of energy transport.
Wave Characteristics
Wave Characteristics
. The
crest of a wave is the point on the medium
which exhibits the maximum amount of positive
or upwards displacement from the rest position.
The trough of a wave is the point on the medium
which exhibits the maximum amount of negative
or downwards displacement from the rest position
The amplitude of a wave refers to the
maximum amount of displacement of a
particle on the medium from its rest
position. The amount of energy carried by
a wave is related to the amplitude of the
wave.
A longitudinal wave is a wave in
which the particles of the medium are
displaced in a direction parallel to the
direction of energy transport.
• A compression is a point on a medium through
which a longitudinal wave is traveling which has
the maximum density. A region where the coils
are spread apart, thus maximizing the distance
between coils, is known as a rarefaction. A
rarefaction is a point on a medium through
which a longitudinal wave is traveling which has
the minimum density.
A tuning fork serves as a useful
illustration of how a vibrating object
can produce sound.
Characteristics of Waves:
Frequency – the number of complete waves
passing a point in space per second; depends
on the source
Wavelength – the distance from a point in a
wave to the next point that wave in the same
phase.
• Light waves will always travel
in a straight line until they hit
a barrier. So whether its
traveling through air, water,
glass, diamond, or any
substance (or none at all),
light travels in a straight
path, until it encounters a
different medium.
All visible objects either emit light or reflect light.
When an object either emits light or reflects it, the
light travels in all directions from the object. If
viewed through a pinhole the light rays
encounter no different medium so they travel
in a straight line.
Waves
• Sound is the movement of energy through
substances in longitudinal
(compression/rarefaction) waves. Sound is
produced when a force causes an object
or substance to vibrate––the energy is
transferred through the substance in a
wave.
Waves Checkpoint 4.6
In the diagram above, at which point are the sound waves being
generated?
A
B
C
D
R
S
T
V