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STAAR Reporting Category 2
Force, Motion, & Energy
Middle School Science
Science STAAR Need to Know
Science STAAR Need to Know
1
Journal Entry
2
3
Problem:
In which position does the ball have
the greatest kinetic energy and least
potential energy?
4
Claim:
5
Scientific Explanation: Position 2
The closer the ball is to the ground, the
greater is its kinetic energy and the least
is its potential energy.
The further away the ball is from the
ground, the greater is its potential
energy and the less is its kinetic energy.
6
Force is a push or pull.
7
PCES
A teenager pulls a rope to the left with a
force of 12 N. A child pulls on the other
end of the rope with a force of 7 N.
The child’s friend adds a force of 8 N,
also pulling to the right. What will
happen?
A.The net force will be 3 N to the right.
B.The net force will be 15 N to the left.
C.The net force will be 12 N to the right.
D.The net force will be 27 N to the left.
8
Problem:
12N
7N
8N
What is the magnitude of the force, and in which direction will
it move?
9
Claim:
10
Scientific Explanation: A
12N
15N
Answer is
3N
11
PCES
Which of the following always
causes change in speed?
A.balanced forces
B.unbalanced forces
C.either balanced or unbalanced
forces
D.any combination of forces
12
Problem:
What type of force
indicates a change
in speed?
13
Claim:
14
Scientific Explanation: B
When an object
increases or decreases
in speed, then the forces
acting on the object are
unbalanced.
15
Journal Entry – Case One
A commentator has described an
athlete as running northwest at 5
m/s. Which attribute of the athlete
has the commentator described?
A. force
B. speed
C. velocity
D. acceleration
16
Problem: Which
attribute of an
athlete is described
in running
northwest at 5m/s.
17
Claim:
18
Scientific Explanation:
Velocity = distance with direction
time
v = d with direction
t
v = d (meters)
with direction
t (seconds)
19
Journal Entry Case Two
Acceleration is also described as the rate at which
velocity changes. Based on the data table below,
what is the acceleration of the ball in m/s2.
Note: The unit for acceleration is m/s2.
20
Problem:
What is the rate of change in velocity
of the ball?
21
Claim:
22
Scientific Explanation:
Rate of change in velocity is called
acceleration.
acceleration = change in velocity
time
= 19.6 m/s - 9.8 m/s = 9.8 m/s
2s
2s
= 4.9 m/s2
23
Problem Solving
Speed, Velocity and
Acceleration Problems
1. A cat ran 50 meters
north of the shopping
center at a velocity of 6
m/s. How long did the
cat run?
d
50 m
s
t
6 m/s
?
north
velocity = 6m/s north
distance = 50 m
time = ?
t = d = 50m = 8.33s
s 6m/s
2. Calculate the velocity
of a car that went a
distance of
135 kilometers north
in 2 hours time.
d
135 km
v
? m/s
north
t
2 hours
velocity = ? north
distance = 135 kilometers
time = 2 hours
v= d =135 km
t
2h
= 67.5 km/h north
3. A ball is thrown a
distance of 20 meters.
What is its speed if it
takes 0.4 seconds to cover
the distance?
d
20 m
s
t
? m/s 0.4 s
speed = ?
distance = 20 meters
time = 0.5 seconds
s = d = 20 m = 50m = 50 m/s
t 0.4 s
s
4. A car is travelling at a
velocity of 500 km/h
for 4 hours south of Arkansas.
What is the total distance
traveled?
d
?
v
500 km/h
south
t
4 hours
velocity = 500 km/h
distance = ?
time = 4 hours
d= v x t = 500km/h x 4 h
= 2000 km
5. What is the
acceleration of a 50 kg
object pushed with a
force of 500 newtons?
F
m
500N
50kg
a
a
F = a
m
2
m/s
500 N= 500 kg.
50kg
50kg
=
2
10m/s
6. If it takes Juan 4 seconds to
run from the batters box to
first base at an average
speed of 6.8 m/s, what is the
distance she covers in that
time?
d
?
s
6.8 m/s
t
4s
speed = 6.8m/s
distance = ?
time = 4 seconds
d = s x t = 6.8m/s x 4s
= 27.2 m
7. A force of 250 N is
applied to an object
that accelerates at a
2
rate of 5 m/s . What is
the mass of the
object?
F
m
250N
m
2
5m/s
a
F = m
a
2
250N = 50N = 10kg.m/s
2
2
2
5m/s
5m/s m/s
= 10kg
8. John ran 50 meters north of
Arlington at a velocity of
6 m/s. How long did he run?
d
50 m
s
t
6 m/s
?
north
velocity = 6m/s north
distance = 50 m
time = ?
t = d = 50m = 8.33s
s 6m/s
Density Problems
1. Calculate the
density of
vegetable oil if
35ml of the oil
weighs 65g.
m
D
65g
D
35ml
v
D = m = 65g
v
35ml
D = 1.85g = 1.85g/ml
ml
2. Find the mass of
250 ml of benzene.
The density of
benzene is 0.82g/ml.
m
D
m
0.82g/ml 250ml
v
m=Dxv =
= 0.82g x 250ml
ml
= 205g
3. What volume of
silver metal will
weigh exactly 250g.
The density of
3
silver is 10.5 g/cm
m
D
250g
3
10.5g/cm
v
v
v = m = 250g
3
D 10.5g/cm
v = 23.80g =
3
g/cm
3
23.80cm
4. 28.5 g of iron is added
to a graduated cylinder
containing 45.5 ml of
water. The water level
rises to the 49.1 ml mark,
From this information,
calculate the density of
iron.
m
D
28.5g
D
49.1ml –
45.5ml
v
m
D
28.5g
D
3.6ml
v
D = m = 28.5g
v
3.6ml
D = 7.91g = 7.91g/ml
ml
Work Problem
Case One
Case Two
Calculate the work done in case one and
case two. Draw a triangle for each case and
show working with units.
Case One
W
W
200N 1 m
F
d
W = F.d
= 200N x 1m
= 200 N.m
= 200 J
Case Two
W
W
400N 0m
F
d
W = F.d
= 400N x 0m
= 0 N.m
=0J
No work has been done.
Identifying Newton’s
Laws of Motion
Which Newton’s Laws
of Motion does each
of the conditions
apply to? Explain
your answer briefly.
1. A person’s body is
thrown forward as a car
comes to a sudden stop.
Newton’s First Law
All objects resist
change in their state
of motion.
2. A picture is hanging
on a wall and does not
move.
st
1
Newton’s
Law
An object at rest will
stay at rest unless
acted by an
unbalanced force.
3. A person not wearing a
seatbelt flies through a car
window when someone
slams on the breaks
because the person’s body
wants to remain in
continuous motion even
when the car stops.
st
1
Newton’s
Law
Due to inertia, the
person wants to
continue to be in a state
of motion even after
brakes are applied.
4.Pushing a child on a
swing is easier than
pushing an adult on
the same swing,
because the adult
has more inertia.
nd
2
Newton’s
Law
Heavier objects
require more force to
move the same
distance as lighter
objects.
5. A soccer ball
accelerates more
than a bowling ball
when thrown with
the same force.
nd
2
Newton’s
Law
The greater the mass
of the object, the
greater the amount of
force needed to
accelerate the object.
6. A soccer player
kicks a ball. The
ball eventually
stops because of
friction.
st
1
Newton’s
Law
An object in motion
will keep moving
unless acted upon
by an unbalanced
force.
7. A student leaves a
pencil on a desk and
the pencil stays in the
same spot until
another student picks
it up.
st
1
Newton’s
Law
An object at rest will
stay at rest unless
acted upon by an
unbalanced force.
8. Two students are in a
baseball game. The first
student hits a ball very
hard and it has a greater
acceleration than the
second student who
bunts the ball lightly.
Newton’s 2nd Law
A greater force applied on an
object of the same mass will
cause it to accelerate faster.
PCES
Problem:
What is the difference between
speed and velocity?
Claim:
Scientific Explanation: G
s=d
t
v=d
t
with direction
PCES
Problem:
What is velocity?
Scientific Explanation: C
velocity = distance with direction
time
=
meters
second
with direction
Journal Entry – Case One
Select the correct answer and explain.
If it takes Juan 4 seconds to run from
the batters box to first base at an
average speed of 6.8 m/s, what is the
distance he covers in that time?
Record your answer and fill in the
bubbles in your answer document.
Problem:
speed = 6.8 m/s
time = 4 s
distance = ?
d
?
s
6.8 m/s
t
4s
time = 4 s
speed = 6.8 m/s
distance = ?
d=sxt
= 6.8 m/s x 4s
= 27.2 m
Case Two
John ran 50 meters north of
Arlington at a velocity of
6 m/s. How long did he run?
Record your answer and fill in
the bubbles in your answer
document.
Problem:
distance = 50 m north
velocity = 6 m/s
time = ?
d
50 m north
v
t
6 m/s
?
velocity = 6 m/s
distance = 50 m north
time = ?
t = d = 50m = 8.33 s
v 6 m/s
PCES
Problem:
When does the marble
experience
unbalanced forces?
Claim:
Scientific Explanation: G
The marble experiences
unbalanced forces when
the speed is increasing or
decreasing.
PCES
Problem:
When will the sled
experience unbalanced
force?
Claim
Scientific Explanation: C
The sled will experience an
unbalanced force when its speed is
increasing in section 2 and
decreasing in section 4.
Journal Entry – Case One
Problem:
Trial 1
time = 4 s
distance = 5.6 m
speed = ?
Trial 1
d
5.6 m
s
t
?
4s
s = d = 5.6 m = 1.4 m
t
4s
s
= 1.4 m/s
Problem:
Trial 2
time = 4 s
distance = 5.6 m
speed = ?
Trial 2
d
7m
s
t
?
5s
s = d = 7 m = 1.4 m
t
5s
s
= 1.4 m/s
average speed
during the two trials
is 1.4 m/s
Case Two
Problem:
What will happen if the force
applied on the car increases from
25 N to 35 N?
H. When force
applied on the car
increases, then the
speed of the car will
increase.
Problem:
Which cart will have the
greatest change in speed
if the same amount of
force is applied?
Claim:
Scientific Explanation: A
Same amount of force is
applied to all the carts.
The cart with 10 g mass is
the lightest. It will have the
greatest change in speed
when pushed.
PCES
Problem:
How does the surface of
the ramp affect the speed
of a car?
Claim
Scientific Explanation: A
The type of material used on
the surface of the ramp
affects the speed of the car.
Journal Entry – Case One
Problem:
How does the mass of the car
affect its stopping time when
brakes are applied?
Scientific Explanation: Both
cars are traveling at the same
speed. The car with less
mass will need less force to
stop it.
Case Two
Problem:
mass = 0.025 kg
force = 5 N
accleration = ?
F
m
5N
0.025kg ?
a
a= F =
5N
m
0.025 kg
2
kg.m/s
a = 200 N = 200
kg
kg
2
a = 200 m/s
Problem:
Which unknown substance
has a density of 2.27
3
g/cm ?
Claim:
Density = mass
volume
m
D
v
Density = mass
volume
4.54g
D
3
2cm
= 4.54
2
3
= 2.27 g/cm
Scientific Explanation: B
Substance 2 has density
3
of 2.27 g/cm .
Carbon has a density of
3
2.27 g/cm .
PCES
Density = mass
volume
m
D
v
Density = mass
volume
14.7g
D
2.2
= 14.7
2.2
= 6.7 g/cm3
3
cm
The answer is J.
Journal Entry – Case One
Problem:
How can we describe
the direction of the
train and its speed?
Scientific Explanation:
The train will move to the left
with increasing speed.
The force will be 3N to the left.
Problem:
Which student did not do
any work on the
container?
W = F. d
W
F
d
Work = Force x distance
Claim:
W
?
F
300 N
d
0m
Scientific Explanation:
Helper Z did not do any
work.
W = F. d
= 300 N x 0 m
= 0 N.m = 0 J
PCES
Problem:
Which example shows that
work is being done?
W = F. d
W
F
d
Work = Force x distance
Claim:
W
?
F
lifting the
small box
d
0.5 m
Scientific Explanation:
Force is applied in
lifting the box, and the
box moves a distance
of 0.5 m from floor to
table. Therefore, work
is done.
Case One
What is the speed of a
ball if it takes 0.6 s to
cover a distance of 30
meters?
d
30 m
s
t
? m/s 0.6 s
speed = ?
distance = 30 meters
time = 0.6 seconds
s = d
t
= 30 m = 50m = 50 m/s
0.6 s
s
Case Two
2 km in 30 minutes
4 km in 60 minutes.
4 km/hour
Energy
The ability to do
work or to cause
change
Science STAAR Need to Know
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Chemical Energy –
Energy transformations
Chemical energy – when light energy from the sun is converted to the
energy in the bonds of the sugar molecules formed in photosynthesis.
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207
Chemical Energy
Examples of chemical
energy changing into
heat energy:
Lighting a match
Burning a wood fire
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208
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209
Electrical energyEnergy transformations
Electrical energy- flow of electrons (a current)
Other ways of generating electricity:
•Water flowing through a dam in a river to move
turbines
•Wind generators that use the energy of moving
wind & operate a generator
•Nuclear power plants convert atomic energy into
heat. Heat boils water to form steam & then
follows the same energy transformations as coal
210
power plantsScience STAAR Need to Know
Many energy transformations…
Electrical to mechanical:
Electricity used to spin the CD (Spinning CD has mechanical energy due to its
position or motion)
Electrical to sound:
A laser converts the digital information on the CD into electrical energy and this
energy goes to the headphones as a vibration- this transmits Sound!
Chemical to electrical:
Batteries store chemical compounds that react when they are used to power
something. This produces a flow of electrons which is electricity!!
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211
Sound energyEnergy transformations
Sound – consists of mechanical
energy waves created by vibrations.
Sound must travel through
something (called “medium” or
“media”) such as air, water, or a
solid.
The medium carries the energy of
the wave from one place to another.
Example: Air transmits the energy
of the vibrating material in the
headphones to your eardrums.
A vacuum is a space that contains little or no matter. Sound
can’t travel through a vacuum since there are no particles to
squeeze together (compression) or spread apart (rarefaction)
Science STAAR Need to Know
212
Light waves do not
need a medium to
transmit energy! They
can even travel through
empty space.
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213
A wave is a disturbance that
transfers energy from one
place to another.
Water waves
are a form of a
wave that
transmits
mechanical
energy across
the surface of
water.
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Seismic waves are caused
by earthquakes that
transmit mechanical energy
through the Earth’s layers.
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216
Potential (PE)
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217
Kinetic Energy (KE)
Energy due to
motion of an
object
Did you know that
the gas burned in
a car engine is
chemical energy
being turned into
Kinetic Energy?
Rubber band
flying through
the air has
kinetic energy
Science STAAR Need to Know
Speed & mass affect
kinetic energy–
Faster/heavier…mor
e Kinetic Energy
218
Potential Energy
Before the yo-yo begins its fall it has stored energy due to its
position. At the top it has its maximum potential energy. As it
starts to fall the potential energy begins to be changed into
kinetic energy. At the bottom its potential energy has been
converted into kinetic energy so that it now has its maximum
kinetic energy
A waterfall has both potential and
kinetic energy. The water at the
top of Bridal Veil Falls has stored
potential energy. When the water
begins to fall, its potential energy
is changed into kinetic energy.
This change in energy also
happens at Niagara Falls where it
is used to provide electricity from
the transformation of mechanical
and electromagnetic energy.
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220
Energy Transformations
Potential energy
A rock sitting at the
top of a cliff
Roller coaster car at
the top peak of a
hill
A swimmer posed to
dive off the end of
a diving board
NO MOTION !!
Kinetic energy
A bouncing ball
A moving roller
coaster
A track star
running
A girl skiing
MOTION is the
key!!!!
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222
A book resting on a desk illustrates balanced forces. However, a book
dropped from a desk illustrates unbalanced forces. In this case,
gravity has overcome the balance of forces.
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223
GRAVITY
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224
You use force to move your body
When you bend your arm,
your muscles contract,
which applies force to your
arm bones. Your arm
responds to this force by
moving.
During breathing, muscles
contract (use force) to move
air in and out of the lungs.
The heart contracts
(uses force) to
pump blood through
the blood vessels,
carrying oxygen to
the muscles.
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225
All living things use force to move
Emerging seedlings
exert force on the
surrounding soil.
This force pushes
the stem of the
plant out of the
ground.
Plants exert
force to open
flower petals,
curl & uncurl
leaves & push
roots through
the soil.
Force is used
to move
materials in &
out of cells.
Science STAAR Need to Know
Fish exert force to
swim by pushing
against the water.226
In order for a force to move something, it must
be an unbalanced force. This means that a
force is stronger in one direction than the
forces in the opposite direction.
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Balanced & Unbalanced Forces
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228
Speed
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Velocity
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Data can be
displayed &
interpreted in many
ways
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231
ACCELERATION
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232
Force & motion are related
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233
ST
1
NEWTON’S
LAW OF
MOTION
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234
ND
2
NEWTON’S
LAW OF
MOTION
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235
RD
3
NEWTON’S
LAW OF
MOTION
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236
Work
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238
A lever is a bar that rests on a support
called a fulcrum which lifts or moves
loads.
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239
Types of levers
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240
This pulley has
1 wheel, so it
changes the
direction of pull
1 time. The
input force is
the same as the
weight using
the pulley.
A pulley is a
simple
machine that
uses grooved
wheels and a
rope to raise,
lower or move
a load. When
a rope passes
over a wheel,
it changes the
direction of
effort (pull)
needed to
move the
load.
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Wedge
A wedge is an object with at least
one slanting side ending in a sharp
edge, which cuts material apart.
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242
An inclined plane is a ramp used to reduce the effort
needed to raise or lower an object over a vertical
height.
It is easier to climb stairs to get to a second floor
than to climb straight up a rope. It is easier to walk
up a long, gentle hill than to climb up a short,
steep hill.
Examples of inclined planes:
Loading ramp; Stairs or wheelchair ramp
Mountain road; Threaded screw.
The ancient Egyptians used inclined planes, or
ramps, to move huge blocks of stone to build the
pyramids.
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A screw is an inclined plane
wrapped around a pole
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244
Wheel & axle
A wheel with a rod,
called an axle, through
its center lifts or moves
loads.
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