Chapter 8: Average Velocity Section 8.1 - The Language of Motion Direction Measuring motion: - Scalar quantity (scalar)- describes the size of a measurement or the amount (number) being counted, a factor knows as magnitude. Only includes magnitude but no direction. Example: you walk 4km/h - Vector quantity (vector)- has both magnitude and direction. Example: You walk 4km/h [E] Distance and Position Distance: - Is a scalar quantity that describes the length of a path between two points or location (d). - The SI unit for distance is meters, m and it is scalar. 47
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Chapter 8: Average Velocity
Section 8.1- The Language of Motion
Direction Measuring motion:
- Scalar quantity (scalar)- describes the size of a measurement or the
amount (number) being counted, a factor knows as magnitude. Only
includes magnitude but no direction.
Example: you walk 4km/h
- Vector quantity (vector)- has both magnitude and direction.
Example: You walk 4km/h [E]
Distance and Position Distance:
- Is a scalar quantity that describes the length of a path between two
points or location (d).
- The SI unit for distance is meters, m and it is scalar.
Example: If you skateboard 10km [E] of your home, you travelled a
distance of 10km.
Position:
- Is a vector quantity that describes a specific point relative to a
reference point.
- The objects location as seen by an observer from a particular
viewpoint.
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Example: If you skateboard 10km [E] and return home in a straight line
along the same route, your position upon returning is 0km because
you are back at your point of origin.
Time and Time Interval Time:
- When an event occurs.
- The SI init is s or h.
Time Interval ∆t:- The duration of an event.
- Final time minus the initial time.
- Scalar quaintly and the SI unit is s or h.
- To calculate: ∆t= tf – ti
Displacement and Distance Displacement ∆d:
- The straight-line distance and direction from one point to another.
- Final position minus the initial position.
∆d = df – di
- How much an object’s position has changed
- The SI unit for displacement is m.
Directions:
- Are designed as positive or negative using vectors.
- North, east, up and right are positive (+).
- South, west, down and left are negative (-)
Uniform Motion Uniform motion:
- Travels equal displacements in equal time intervals.
- Will not speed up or slow down and they would not change direction.
A Motion Diagram:
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- Shows the object’s position at given times and allows us to picture or
visualize motion.
- You can identify the position of the ball at corresponding time intervals.
Position time graph:
- When you plot the time data on the horizontal axis (x) and the position
data on the horizontal axis (y).
- Uniform motion is representing by a straight line on a position-time
graph.
Best-fit line:
- A smooth curve or straight line that most closely fits the general shape
outline by the points, to graph real motion.
- Positions and times not given as data can be estimated by finding the
location corresponding to a specific time and position on a best-fit line.
Slope Slope:
- A slope of a graph refers to whether a lone is horizontal or goes up or
down at an angle.
Positive:
- Slants up to the right indicating that an object’s position, from the origin
is increasing with respect to time.
Zero:
- A zero slope is a straight, horizontal line.
- It represents an object at rest.
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Negative:
- A negative slope slants down to the right, indication an object is
mobbing in a negative direction- left, down, west or south.
Section 8.2- Average Velocity
Speed and Velocity Speed v:
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- The distance an object travels during a given time interval divided by
the time interval.
- Speed is a scalar quantity.
- The SI unit for speed is meters per second m/s.
Velocity:
- The displacement of an object during a time interval divided by the
time interval.
- Velocity describes how fast an object’s position is changing.
- The SI init for velocity is meters per second m/s.
Same Speed, Different Velocities:
- Objects travelling at the same speed can have different velocities.
- Imagine two escalators travelling at the same speed, one going up and
the other going down.
- Because they are travelling in opposite directions, one of the directions
has a negative sign (which means different velocities.)
Slope:
- Velocity can be determined from the slope of a position-time graph,
- Slope is calculated- Slope= rise/run or ∆d/∆t
Average Velocity Average Velocity:
- The rate of change in position for a time interval.
- It is almost impossible for an object to move at a perfectly uniform rate
because of many factors like wind or uneven surface,
- Is a vector and includes a direction.
Position-time Graph and Average Velocity:
- if moving away from the origin it’s considered positive.
- A positive slope represents the average velocity of the object moving
away from the origin.
- A horizontal line, which has zero slope, represents an object at rest.
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- A negative slope, represents the average velocity of the object moving
back toward the origin.
Chapter 9: Acceleration
Section 9.1- Describing Acceleration
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Changes in Velocity Change in Velocity:
- occurs when the speed of an object changes, or its direction of motion
changes or both.
- To find changes in velocity, subtract the initial velocity from the final
velocity. ∆v = vf – vi
Acceleration Acceleration:
- The rate at which an object changes its velocity.
- When talking about acceleration, we need to include the magnitude of
the change in velocity of the moving object and need to indicate the
change in direction of the object’s velocity.
Positive and Negative Acceleration:
- When something’s speed is increasing, it has a positive acceleration.
- When something’s speed is decreasing, it has a negative acceleration.
Declaration:
- Acceleration that is opposite to the direction of motion.
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Direction
Factor Velocity Acceleration Increase in speed while travelling