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STANDARD 2a
• Students know a force has both
direction and magnitude
FORCES
• A force is a push or a pull
• Force is a vector with a magnitude
(strength) and a direction in which it is
exerted
• Arrows are used to represent force
• SI unit for the magnitude of a force is
the newton (N)
• A spring scale is used to measure the
amount of force on an object
FORCES
104. 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
ANSWER: D
STANDARD 2b
• Students know when an object is
subject to two or more forces at
once, the result is the cumulative
effect of all the forces
FORCES
• The combination of all the
forces acting on an object is
called the net force
• When the combined forces act
in the same direction, add all
the forces to find the net force
• When forces act together in
opposite directions, subtract the
forces to find the net force
FORCES
107. Robin and Wes push on opposite
sides of a wheeled chair. Robin pushes
with a force of 80 N to the left. Wes
pushes with a force of 100 N to the
right. What is the resulting force on the
chair?
A 20 N to the left
B 20 N to the right
C 180 N to the left
D 180 N to the right
ANSWER: B
FORCES
• Robin and Wes are now pushing the wheeled
chair in the same direction. Robin pushes
with a force of 80 N to the left and Wes pulls
with a force of 120 N to the left. What is the
resulting force on the chair?
A 40 N to the left
B 40 N to the right
C 200 N to the left
D 200 N to the right
ANSWER: C
STANDARD 2c
• Students know when the forces
on an object are balanced, the
motion of the object does not
change
FORCES
• Equal forces acting on
one object in opposite
directions are called
balanced forces
• For an object that is not
moving, the result of
balanced forces is no
motion
• For an object that is
moving, the result of
balanced forces is
constant velocity
FORCES and MOTION
FIRST LAW OF MOTION
An object will continue in
motion or remain at rest
when all forces acting on it
are equal in magnitude and
direction.
This is also called inertia,
the tendency of an object to
resist change in motion
FORCES
108. Two students on opposite sides of a box
apply forces to the box. What must be true if
the box does not accelerate?
A The forces are balanced
B The forces are unbalanced and in the
same
direction
C The forces are unbalanced and opposite,
with
the greater force to the left
D The forces are unbalanced and opposite,
with
the greater force to the right
ANSWER: A
FORCES
110. A person falls from a plane and reaches
terminal velocity. At this point the downward
force of gravity on the person is equal to the
upward force of air resistance on that person.
As the person falls he will
A slow down
B speed up
C fall at a constant speed
D None of the above
ANSWER: C
STANDARD 2d
• Students know how to identify
separately the two or more forces
that are acting on a single static
object, including gravity, elastic
forces due to tension or
compression in matter, and
friction
FORCES
• Types of Forces
– Gravity – an attractive force that objects
exert on each other.
– The force depends on the masses and
distances of the objects. More mass,
more gravity; greater distance, less gravity
FORCES
• Types of Forces
– Elastic – the force in an object that
resists tension (stretching) or
compression (pressing). Examples:
rubber band or a spring
FORCES
• Types of Forces
– Friction – a force
that resists the
motion between
two surfaces in
contact.
Examples: static,
sliding, rolling,
fluid (air or water
resistance)
FORCES
112. The diagram
shows a book sitting
on a table. The
force of the table
pushing up on the
book is called
A gravity
B tension
C compression
D static friction
ANSWER: C
FORCES
114. Suppose the wheels on
the cart in the diagram are
locked in place. If the
force applied by the girl is
balanced, so that the cart
does not move, what is the
cause of the balanced
force?
A static friction
B sliding friction
C rolling friction
D fluid friction
ANSWER: A
FORCES
115. Emma wants to determine the
strength of the force of gravity between
two objects. What should she
measure?
A the mass of each object and the
distance
between them
B the size and weight of each object
C the electrical charge of each object
D the weight of each object and the
distance between them
ANSWER: A
FORCES
116. A yo-yo hangs from a string and
does not move. What forces act on the
yo-yo?
A gravity only
B tension only
C gravity and tension
D no forces act on the yo-yo
ANSWER: C
STANDARD 2e
• Students know that when the
forces on an object are
unbalanced, the object will
change its velocity (that is, it will
speed up, slow down, or change
direction)
FORCES
• SECOND LAW OF MOTION
–When the forces on an object
are unbalanced (not equal),
the object will change its
velocity, that is, it will speed
up, slow down, or change
direction.
STANDARD 2f
• Students know the greater the
mass of an object, the more force
is needed to achieve the same
rate of change in motion
FORCES
• SECOND LAW OF MOTION
– Force = mass x acceleration
–Acceleration = Force / Mass
–The greater the mass of an object
the more force is needed to
achieve the same rate of
acceleration
FORCES and MOTION
THIRD LAW OF MOTION
For every action force there is an equal
and opposite reaction force
Identify the action/reaction pairs?
FORCES
Centripetal force is any force that
causes an object to move in a circular
path
• Bernoulli’s Principle states that the
faster a fluid moves, the less pressure
the fluid exerts.
• An airplane wing is designed so that the
air above the wing moves faster than
the air below the wing. The air pressure
below the wing becomes greater than
the air pressure above the wing. This
creates unbalanced forces above and
below the wing and helps produce lift,
FORCES and MOTION
What forces are acting on this object?
gravity & air resistance
FORCES and MOTION
117. What conclusion can you draw by looking
at the diagram?
A Air resistance in front of the balloon
pushes it
backwards
B Gravity forces air out of the balloon’s open
end
C The force of the air leaving the balloon
causes it to accelerate forward
D Friction causes the balloon’s acceleration
to decrease
ANSWER: C
FORCES
119. What force keeps the moon in orbit
around the Earth?
A inertia
B gravitational force
C net force
D centripetal force
ANSWER: B
FORCES
120. If the net force on a chair is 6 N to
the right, what will occur?
A The chair will accelerate to the right
B The chair will accelerate to the left
C The chair will have no velocity
D The chair will not move
ANSWER: A
FORCES
122. The two skaters push
against each other’s hands.
Both skaters move backward.
What do you know about the
forces acting on the skaters?
A Skater X applied greater
force than Skater Y
B Skater Y applied greater
force than Skater X
C The forces on the skaters
were balanced
D The forces on the skaters
were unbalanced
ANSWER: D
FORCES
123. If an equal force is applied to four
different objects, which will accelerate
the most?
A the one with the least acceleration
B the one with the least density
C the one with the least mass
D the one with the least velocity
ANSWER:
C
FORCES
124. Four objects roll across a smooth
floor at the same speed. The objects
have different masses and diameters.
Which object will require the greatest
force to increase its speed by 1 m/s?
A the object with the greatest diameter
B the object with the least diameter
C the object with the greatest mass
D the object with the least mass
ANSWER:
C
STANDARD 2g
• Students know the role of gravity
in forming and maintaining the
shapes of planets, stars, and the
solar system
FORCES
• The force of gravity caused matter to come
together to form the first stars.
• Gravity caused stars to gather together to
form galaxies
• Gravity pulled clouds of gas and dust
together to form the sun and the planets
• Gravity is the force that keeps the planets and
other bodies in the solar system in orbit
around the sun
• The sun is stable because the forces within it
are balanced. Pressure caused by nuclear
fusion in the sun’s center pushes the sun’s
matter outward, while gravity provides an
equal and opposite force pulling the sun’s
matter inward
FORCES
126. The sun was formed when
A the big bang blew up the solar
system
B gravity pulled matter into the center
of a
spinning cloud of gas and dust
C fluid friction caused several planets
to come together
D two stars collided in the center of a
cloud of gas and dust
ANSWER:
B
STANDARD 8a
• Students know density is mass
per unit volume
Density
• Density - the amount of mass in a given
volume
Mass
Density 
Volume
Density Units
g/cm3 for solids
g/mL for liquids
1cm3 = 1mL
Low Density
High Density
DENSITY
127. When
a sample of liquid is
divided in half, its density
A is half as much
B stays the same
C is two times greater
D is four times greater
ANSWER: B
DENSITY
128. Density is used to determine all
of the following except
A the force of gravity
B the buoyancy of an object
C the purity of a substance
D the identity of an unknown
substance
ANSWER: A
DENSITY
129. Which unit is used to express the
density of a substance?
A m/kg3
B g/cm3
C mL/cm3
D kg/cm
ANSWER: B
STANDARD 8b
• Students know how to calculate
the density of substances (regular
and irregular solids and liquids)
from the measurements of mass
and volume
DENSITY
• Mass of a substance is measured
on a balance
• Volume of a liquid is measured
with a graduated cylinder
• Volume of a regular solid =
length x width x height
• Volume of an irregular solid is
measured using water
displacement method
DENSITY
130. A scientist has a beaker with 150 mL
of gasoline. The mass of the gasoline is
108 g. What is the gasoline’s density?
A 0.72 g/mL
B 1.1 g/mL
C 1.4 g/mL
D 1.5 g/mL
ANSWER: A
DENSITY
131. Pure copper has a density of 8.9
g/cm3. What is the mass of a 10-cm
cube of copper?
A 8.9 g
B 89 g
C 890 g
D 8,900 g
ANSWER:
B
DENSITY
134. The rock in
the diagram has
a mass of 58.8 g.
What is the
rock’s density?
A 1.3 g/mL
B 2.0 g/mL
C 2.6 g/mL
D 2.8 g/mL
ANSWER: D
DENSITY
135. Which of the following substances is
a gas?
Substance
Density (g/cm3)
A
.15
B
.04
C
.000018
D
2.1
ANSWER: C
STANDARD 8c
• Students know the buoyant force
on an object in a fluid is an
upward force equal to the weight
of the fluid the object has
displaced
BUOYANCY
Buoyancy –
upward force a
fluid (liquid or
gas) exerts on
any object in
the fluid
Buoyancy
• The buoyant force on
an object is equal to
the weight of the
volume of fluid
displaced by the
object
• Buoyant force exists
because there is
more pressure on
bottom of object than
on top (pressure
increases as depth
increases)
BUOYANCY
136. A beach ball pops out of water
because the buoyant force is
A greater than the ball’s weight
B equal to the ball’s weight
C less than the ball’s weight
D greater than the ball’s buoyant force
ANSWER:
A
BUOYANCY
137. Why does a ship float, when a solid
block of steel of equal weight sinks?
A the ship has less buoyant force
B the steel block has more buoyant
force
C the ship displaces more water
D the steel block displaces more water
ANSWER:
C
BUOYANCY
138. An air-filled balloon falls to the
ground because
A air cannot hold up objects
B it weighs more than the weight of the
air it displaces
C the buoyant force of the balloon is
greater than the buoyant force of air
D the balloon has less surface area
than air
ANSWER: B
BUOYANCY
139. The buoyant force in
container A is
A greater than the buoyant
force in container B
B the same as the buoyant
force in container B
C less than the buoyant
force
in container B
D zero
ANSWER: A
BUOYANCY
140. In each container, the
buoyant force equals
A the density of the
object
B the force of gravity on
the object
C the mass of the object
D the weight of the
displaced fluid
ANSWER: D
STANDARD 8d
• Students know how to predict
whether an object will float or sink
BUOYANCY
• An object will float
if its weight is less
than the buoyant
force acting on it
• An object will sink
if its weight is
greater than the
buoyant force
acting on it
BUOYANCY
• An object will float
if its density is
less than the
density of the fluid
• An object will sink
if its density is
greater than the
density of the fluid
BUOYANCY
141. Will this object float in water?
A No, because it is more dense than
water
B No, because it is less dense than
water
C Yes, because it is more dense than
water
D Yes, because it is less dense than
water
ANSWER: D
BUOYANCY
142. Which item(s) in the table sink in gasoline?
A maple wood
B graphite and seawater
C paper, graphite, and seawater
D paper, graphite, seawater, and maple
wood
ANSWER: C
BUOYANCY
144. A canoe floats at the edge of a pond.
If the volume of pond water displaced
by the canoe weighs 90 N, what is the
buoyant force of the water on the
canoe?
A 45 N
B 90 N
C 135 N
D 180 N
ANSWER: B