Class Notes for Accelerated Physics

1
Class Notes for Accelerated Physics
Uniform Circular Motion Review

• Mr. Lyzinski
• CRHS-South

2
What could be on the test?

• Using the velocity, period, frequency,
  acceleration equations to find either v, T,
  f, or ac.
• 2) Drawing full FBDs of car traveling around a
  flat, frictionless circular turn
• car traveling around a flat, circular turn w/
  friction
• car/plane traveling around a banked,
  frictionless turn
• a simple swing ride (conical pendulum)
• a ball on a string in a Horizontal OR
  Vertical circle
• a bike/car/plane doing a loop-de-loop
• a bike/car doing a woop-de-doo (dip and/or
  bump)
• a miscellaneous object traveling in a
  circular path
• 3) Questions like What is supplying the
  centripetal force in ______ situation?

Skip for accelerated physics
3
What could be on the test? (continued)

• 4) Using the centripetal force equation in each
  of the following situations
• - car traveling around a flat, frictionless
  circular turn
• - car traveling around a flat, circular turn w/
  friction
• - car traveling around a banked, frictionless
  turn
• - a simple swing ride (conical pendulum)
• - a ball on a string in a Horizontal OR
  Vertical circle
• - a bike/car/plane doing a loop-de-loop
• - a bike/car doing a woop-de-doo (dip and/or
  bump)
• - a miscellaneous object traveling in a
  circular path
• - a plane pulling a banked, circular turn
• - finding the critical speed necessary to
  complete a vertical loop.
• Finding the tension in the rope (or the normal
  force on the track) at the top and bottom of a
  vertical loop.

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What could be on the test? (continued, again)

• Finding the apparent weight (otherwise known as
  FN) at the bottom of a vertical loop.
• Calculating the of Gs pulled at the bottom of
  a circular loop
• 9) Basic knowledge of the terms Period,
  Frequency, etc.
• 10) Finding the maximum speed that you can go
  before losing contact with the ground on a
  woop-de-doo bump.
• The difference b/w Centripetal and
  Centrifugal
• Finding the maximum velocity that a ball on a
  string can swing at, and finding the minimum
  velocity needed to complete a circular loop.

Skip for accelerated physics
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Knowing the basic equations

• Period the time needed to complete 1 full
  revolution.
• Frequency the of revolutions completed in 1
  second.
• Velocity Constant in magnitude for circular
  motion, but the change in its directions causes
  the centripetal acceleration.
• Centripetal Acceleration Always directed
  inward!!!
• Centripetal Force The force that keeps an
  object (which wants to move in a straight line
  due to inertia) in circular motion. If an object
  is moving in a circle, SOMETHING must be
  supplying the centripetal force.

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Centripetal vs. Centrifugal
Imagine swinging a rock on a rope. A moving
object tends to remain in motion and move in a
straight line (Newtons 1st Law!!!!). In order to
make the rock move out of a straight line into a
circle, you have to keep pulling on the rope.
The inward pulling force is the "centripetal"
force.But your hand feels the rope pulling it
outward. This outward pulling force is called
the "centrifugal" force. HOWEVER, the
centrifugal force doesnt really exist. It is
simply the result of the object wanting to remain
in motion on its original path (due to inertia).
NEVER, EVER use the term or the notion of
centrifugal force. Centripetal force is always
directed toward the center of the curve. If
centrifugal force did exist (which it doesnt),
it would always be directed away from the center.
Note Centrifugal means " to flee the center"
and Centripetal means "to seek the center"
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Ball on a string swinging in a horizontal circle
A car traveling around a flat circular turn.
What supplies the centripetal acceleration in
each case????
A car traveling around a banked, FRICTIONLESS
circular turn
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A car traveling around a banked, circular turn
(and wanting to slide down the turn)
A car traveling around a banked, circular turn
(and wanting to slide up the turn)
What supplies the centripetal acceleration in
each case????
9
A simple swing ride (conical pendulum)
Ball on a string swinging in a vertical circle
What supplies the centripetal acceleration in
each case????
10
Bike or a car doing a loop-de-loop
Airplane doing a loop-de-loop
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Bike or a car doing a woop-de-doo
SKIP FOR ACCELERATED PHYSICS
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For each of the previous FBDs, make sure you can
do the following

• answer the question what is supplying the
  centripetal force.
• 2) write the equation Fc mac and be able to
  appropriately fill in the Fc term.

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Key Equations to know (Horizontal)
Horizontal circles
Fc Ff (mFN) Fc Tension Fc force of
adhesion Fc force of attraction between 2
objects
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Key Equations to know (Vertical)
Can you derive each of these equations????
Car doing Loop-de-loop
Plane doing Loop-de-loop
Ball on String
Pilot doing Loop-de-loop
At top At Bottom At Side Critical Speed
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Ill re-derive one set of equations for you ?
Ball on a string traveling in a vertical circle
v
mg
T
Assuming a constant speed
R
At top
T
At bottom
Forces pointing in are positive.
At side
mg
If moving too slow, the tension will become zero
at the top (the ball will fall ?)
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HOMEWORK

• Uniform Circular Motion Review Packet
• (all 11 problems)
• Solutions will be posted online