Transcript 8th Grade Science Review

8th Grade Science Review
What We Have
Learned This Year
Standard 1
Motion
The velocity of an object
is the rate of change of
its position.
Standard 1
Motion
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To determine if motion is occurring compare
the object to a reference point.
Speed= distance
time
Velocity shows speed and direction.
Acceleration is a change in velocity (speed or
direction).
Graph showing Speed
2.5
1.5
1
0.5
0
10
20
30
meters
40
seconds
2
Bob
Jane
Question 1
An athlete can run 9 kilometers in 1 hour. If the
athlete runs at that same average speed for 30
minutes, how far will the athlete travel?
a. 18 kilometers
b. 9 kilometers
c. 4.5 kilometers
d. 3.3 kilometers
Question 2
How much time is required for a bicycle to
travel a distance of 100m at an average
speed of 2 m/s?
a. 0.02 s
b. 50 s
c. 100 s
d. 200 s
Question 3
Which of the following represents the velocity
of a moving object?
a. 40
b. 40 m north
c. 40 m/s
d. 40 m/s north
Question 4
The graph shows the speed of a vehicle over time.
How far did the vehicle travel during the first two
seconds?
a.
b.
c.
d.
0.2
5m
10 m
20 m
Question 5
The graph shows how the position of an object
changes over time.
What is the speed of the object during the time interval
from 4 seconds to 10 seconds?
a.
b.
c.
d.
2 m/s
3 m/s
8 m/s
16 m/s
Standard 2
Forces
Unbalanced forces
cause changes in
velocity.
Standard 2
Forces
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A push or pull
A force has magnitude and direction.
When forces are unbalanced, the object will
move.
When forces are balanced an object will not
move.
The greater the mass of an object, the more
force will be needed to move it.
Standard 2
Forces
Question 1
A force is acting on each of the objects.
What can be concluded about these forces?
a. They are the same because they point
toward the objects.
b. They are the same because they have the
same magnitude.
c. They are different because they have
different magnitudes.
d. They are different because they have
different directions.
Question 2
The students are pushing a cart as shown. The
cart will move as if it were acted on by a
single force with a magnitude of
a. 50 N
b. 150 N
c. 200 N
d. 350 N
Question 3
A ball is dropped from the top of a tall building.
As the ball falls, the upward force of air
resistance becomes equal to the downward
pull of gravity. When these two forces
become equal in magnitude, the ball will
a.
b.
c.
d.
flatten due to the forces.
fall at a constant speed.
continue to speed up.
slow to a stop.
Question 4
Four forces are acting on a box as shown. This
box will increase in speed
a. downward and to the left.
b. downward and to the right.
c. upward and to the left.
d. upward and to the right.
Question 5
A force of 5 N is required to increase the speed of a
box to a rate of 1.0 m/s to 3.0 m/s within 5 s along a
level surface. What change would most likely require
additional force to produce the same results?
a.
b.
c.
d.
reduce the mass of the box
increase the mass of the box
make the surfaces of the box smooth
make the surfaces of the floor smooth
Standard 8
Density and Buoyancy
All objects experience a
buoyant force when
immersed in liquid.
Standard 8
Density and Buoyancy
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Density = mass
volume
The buoyant force on an object in a fluid is
an upward force equal to the weight of the
fluid it has displaced.
Standard 8
Density and Buoyancy
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Know how to measure mass and volume to
calculate density.
An object will float in water if the density is
less than 1.0 g/ml.
Standard 8
Density and Buoyancy
Question 1
What is the density of a 64 g iron cube that
displaces 8 ml of water?
a. 512 g/ml
b. 32 g/ml
c. 8 g/ml
d. 4 g/ml
Question 2
A piece of pine wood floats on the surface of a lake
because the water exerts
a. an upward force equal to the weight of the wood.
b. a downward force equal to the weight of the
wood.
c. an upward force equal to the weight of the
displacement water.
d. a downward force equal to the weight of the
displacement water.
Question 3
The following table shows properties of four
different sample materials. One of these
materials is cork, a type of wood that floats in
water.
Given that the density of water is 1 g/ml, which
of the samples is most likely cork?
a. 1
b. 2
c. 3
d. 4
Question 4
The densities of four different woods are
shown.
Which wood will sink when placed in a fluid
with a density of 1.14 g/cm3
a. African teakwood
b. balsa
c. cedar
d. ironwood
Standard 9
Investigation and Experimentation
Scientific progress is made
by asking meaningful
questions and conducting
careful investigations.
Standard 9
Investigation and Experimentation
Step of the Scientific Method
 Step 1 – State the problem
 Step 2 – Gather Information
 Step 3 – Form a hypothesis
 Step 4 – Conduct an experiment
 Step 5 – Form a conclusion
 Step 6 – Share results
Standard 9
Investigation and Experimentation
Question 1
The graph below shows the movement of an
object at several points in time.
What is the average speed of the object?
a. 0.5 meters/minute
b. 2 meters/minute
c. 25 meters/minute
d. 50 meters/minute
Question 2
Data from an experiment are presented.
The slope of the graph represents what
characteristic of an object?
a. displacement
b. force
c. speed
d. inertia
Question 3
A spring scale is pulled downward and
readings are recorded.
If the spring scale is pulled 3.5 cm, the spring
scale should read
a. 12 N.
b. 13 N.
c. 14 N.
d. 15 N.
Question 4
A student records the mass and volume of a lump of clay, x. Next,
a second lumps of clay, y, is added to lump x, and the
combined (x + y) mass and volume are recorded. Finally, a
third lump of clay, z, is added to the combined (x + y) mixture
and the final (x + y + z) mass and volume are recorded, as
shown.
What is the most logical conclusion about the clay used in this
investigation?
a. Lump z has the greatest mass.
b. Lump z has the lowest density.
c. Lump y has the lowest density.
d. Lump y has the greatest mass.
Question 5
Red-clay bricks have a density of
approximately 200 kg/m3. Air has a density of
1 kg/m3. Which of the following has the
lowest mass?
a. 2 m3 of bricks
b. 4 m3 of bricks
c. 6000 m3 of air
d. 10,000 m3 of air