Transcript 2B.1.1: Friction

Physical Science State
Assessment Review
S.HS.2B.1.1
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Newton’s First Law of Motion (law
of inertia) – an object in motion stays in
motion at a constant velocity and an
object at rest stays at rest unless acted
upon by an outside force
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This outside force is usually friction.
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friction – a force that acts between
two materials that are in contact with
each other as they move past one
another
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The more smooth a surface is, the less
friction it applies.
Only when friction is present do we need a
force to keep the object moving. Without
friction a moving object would never stop.
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Types of friction:
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sliding friction – when two surfaces slide
past each other
rolling friction – when a round object rolls
over a flat surface
fluid friction – friction between a fluid (any
liquid or gas) and the surface of an object
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Air resistance is a type of fluid friction.
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Air Resistance:
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All objects, regardless of their size or mass,
accelerate toward the surface of the Earth at a
rate of 9.8 m/s/s.
Gravity is the force that causes this acceleration.
As objects fall they experience friction with the air
(fluid friction).
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This air resistance is a force that acts in the opposite
direction of gravity.
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terminal velocity - – the point at
which a falling object stops accelerating
because the force of air resistance
becomes equal to the force of gravity
Questions
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1. An object is pushed with a force and
begins to move across a frictionless surface.
Which best describes the object’s motion
after the force stops acting?
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A.
B.
C.
D.
constant velocity
increasing velocity
variable acceleration
decreasing acceleration
Questions

1. An object is pushed with a force and
begins to move across a frictionless surface.
Which best describes the object’s motion
after the force stops acting?
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A. constant velocity – correct answer
B. increasing velocity
C. variable acceleration
D. decreasing acceleration
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2. An object is pushed with a force and
experiences friction. Which best
describes the motion of this object after
the force stops acting?
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A.
B.
C.
D.
constant velocity
increasing velocity
variable acceleration
decreasing velocity
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2. An object is pushed with a force and
experiences friction. Which best
describes the motion of this object after
the force stops acting?




A.
B.
C.
D.
constant velocity
increasing velocity
variable acceleration
decreasing velocity – correct
answer
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3. Which of the following statements
best describes air resistance?
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A. The rolling friction experienced
between an object and the air.
B. A force of gravity.
C. The fluid friction experienced between
an object and the air as the object falls.
D. The sliding friction experienced
between an object and the air.
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3. Which of the following statements best
describes air resistance?
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A. The rolling friction experienced between an
object and the air.
B. A force of gravity.
C. The fluid friction experienced between
an object and the air as the object falls. –
correct answer
D. The sliding friction experienced between an
object and the air.
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4. Choose the surface or substance
that would apply the greatest amount
of friction.
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A.
B.
C.
D.
air
a tile floor
a carpeted floor
motor oil
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4. Choose the surface or substance
that would apply the greatest amount
of friction.
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A. air
B. a tile floor
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C. a carpeted floor – correct answer
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D. motor oil
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