Acceleration
Objects moving with constant acceleration
What is acceleration?
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Acceleration is ANY change in an object’s
velocity.
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This can mean the object is:
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Speeding up
Slowing down
Changing direction
In all cases the VELOCITY is changing!
Forward or Backward?
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Acceleration can happen when a object is
moving forward OR backward.
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For now, we will only consider objects
moving forward.
Review---Velocity
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Average velocity: velocity over a given time
interval.
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Instantaneous velocity: velocity right now.
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Think of the speedometer in your car.
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This shows instantaneous velocity.
Acceleration
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Is acceleration a scalar or a vector?
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Hint: Vectors have direction---scalars do not.
It’s a Vector!!
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Acceleration is a vector…. Because it
includes a direction!!!
Some examples of acceleration…
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A car is sitting motionless at a stoplight, then
the driver hits the gas.
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A plane lands on a runway traveling 150 mph
and then comes to a complete stop.
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A student is walking slowly to class but then
hears the 2 min bell and starts to run.
What types of objects can accelerate?
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Describe at least 2 situations in which an
object is accelerating other than the examples
provided.
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You will be asked to provide one of them as
part of your exit pass today.
What makes things accelerate?
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A force (any push or pull)
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Or Gravity!! Objects accelerate when they
are falling.
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We will discuss this in detail during the next unit.
“Seeing” Acceleration
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Which car or cars (red, green, and/or blue) are undergoing an
acceleration?
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Study each car individually in order to determine the answer.
Red, Green or Blue?
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Now that you've answered the first question correctly….(it
was just the green and blue cars)
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Try this one: which car experiences the greatest acceleration?
Blue!
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The BLUE car has greater acceleration,
because its velocity is changing at a greater
rate!!
Red, Green or Blue?
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As a final test of your understanding, consider the positiontime graph at the right. Each one of the three lines on the
position-time graph corresponds to the motion of one of the
three cars. Match the appropriate line to the particular color
of car.
Which one is which?
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RED- Moving with
constant velocity---so it
must be B.
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BLUE- is A ---greatest
change in velocity.
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GREEN- is C---smaller
change in velocity.
Hot Wheels Track
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Describe when the car is accelerating. Hint: there are multiple times this
happens.
Exit Pass: Use complete sentences!
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How is instantaneous velocity different from
average velocity?
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Define acceleration.
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Give a real life example of a situation when
an object is accelerating.