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