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Chapter 10 Motion
Section 1: Measuring Motion
Observing Motion
•
___________ is an object’s change in position relative to a _____________________________.
• reference point = stationary object used to determine whether an object is moving
• most common reference point is Earth
• common reference directions include: N, S, E, W
•
__________________ is the change in the position of an object.
• ____________________ measures the path taken. (ACTUAL path of motion)
• Displacement is the ___________________________________. Displacement must
always indicate ____________________. (CHANGE in position of an object)
Speed and Velocity
•
_______________ is the distance traveled divided by the time interval during which the motion
occurred. Speed describes ________________________________________.
•
Speed measurements involve __________ and __________.
•
•
The SI units for speed are ________________________________________________.
When an object covers equal distances in equal amounts of time, it is moving at a
__________________________.
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Speed can be studied with graphs and equations.
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Speed can be determined from a distance-time graph. When an object’s motion is graphed by
plotting distance on the y-axis and time on the x-axis, the slope of the graph is speed.
•
Average speed is calculated as distance divided by time.
Equation for Average Speed
speed = ____________
•
v = ___
_____________________________________ is the speed at a given point in time.
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____________________ is the _________ of an object in a ______________________________.
•
Velocity describes both the speed and the direction.
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Combine velocities to determine the resultant velocity.
Math Example- Velocity
Metal stakes are sometimes placed in glaciers to help measure a glacier’s movement. For several days in
1936, Alaska’s Black Rapids glacier surged as swiftly as 89 meters per day down the valley. Find the
glacier’s velocity in m/s. Remember to include direction.
A. Given:
B. Unknown:
C. Conversion factors? we want time in seconds!!!!
1 day = 24 hrs
1 hr = 60 min
1 min = 60 sec
D. Solve: write correct formula then plug in numbers, circle answer with units.
Determining Speed with a Graph
*Independent Variable = ______________ = placed on _____________
*Dependent Variable = _______________ = placed on _____________
*Speed = slope = ∆y/∆x = ∆distance/ ∆time = d/t
∆ = “change”
Section 2: Acceleration
Acceleration and Motion
• ______________________________ is the rate at which velocity changes over time.
•
An object accelerates if its _______, ____________________, or both change.
•
Acceleration can be a change in __________.
•
Acceleration can be a change in ____________________.
•
Uniform circular motion is constant acceleration.
Calculating Acceleration
• Acceleration is the rate at which velocity changes.
• Acceleration Equation (for straight-line motion)
acceleration = ________________________________
OR
a = Vf - Vi
t
• In SI units, acceleration is measured in meters per second per second (_______) or _________.
Calculating Acceleration:
A flowerpot falls off a second-story windowsill. The flowerpot starts from rest and hits the sidewalk 1.5 s
later with a velocity of 14.7 m/s. Find the average acceleration of the flowerpot.
A. Given :
B. Unknown:
C. Conversion Factors? None
D. Solve: write correct formula then plug in numbers, circle answer with units.
Section 3: Motion and Force
Balanced and Unbalanced Forces
•
_______________is an action exerted on a body in order to change the body’s state of rest or
motion. Force has magnitude and direction.
• The _________________________ is the combination of all forces acting on an object.
•
Objects subjected to ______________________ either do ____________ or move at
___________________.
•
An ________________________ must be present to cause any change in an object’s state of
motion or rest.
The force of Friction
• _______________________ is a force that opposes motion between two surfaces that are in
contact.
•
Friction ____________________________________________________________.
•
_____________________________ resists the initiation of sliding motion between two surfaces
that are in contact and at rest.
•
_____________________________ opposes the movement of two surfaces that are in contact and
are sliding over each other.
•
Static friction is greater than kinetic friction.
• There are many different types of kinetic friction, such as sliding friction and rolling
friction.
• Fluid friction, such as air resistance, also opposes motion.
Friction and Motion
• Friction can be ____________________ or ______________________.
• Friction is necessary to roll a vehicle or hold an object.
• However, friction can also cause excessive heating or wear of moving parts.
•
Harmful friction can be ________________.
•
Helpful friction can be _________________.