Transcript Standard EPS Shell Presentation

Foundations of Physical
Science
Workshop: The Loop Track
The Loop Track
CPO Science
Key Questions
 Why does a
roller coaster
stay on the
track when it
is upside
down on a
loop?
Roller Coasters
www.rcdb.com
The CPO Loop Track
Investigate Motion of Marble
 Drop the marble from different heights
and observe whether or not it
successfully completes the loop.
 Where on the track is the lowest point
the marble can be released from and
makes it all the way around
SUCCESSFULLY?
 What is the criteria for judging whether
or not the marble stays on the track?
Release Height and Success
 In your own words describe the
relationship between the marble
making it all the way around the
loop and release height
 Can you propose an explanation
for the relationship?
How fast does the marble
need to be moving?
 Drop the marble from the
lowest point on the track that
still makes it all the way around
the loop SUCCESSFULLY
 Measure the speed of the
marble at the top of the loop
Investigate Motion of Marble
 How would you calculate the
speed?
CPO Timer or Data Collector
 Setup
 Photogates
Collect Data
 Use the CPO Timer or Data
Collector with a photogate to see
how long it takes the marble to
break the light beam at the top of
the loop
 Calculate the minimum speed
required to make it all the way
around the loop
Does MASS make a
difference?
 State your hypothesis
 Propose and perform an
experiment to test your hypothesis
 Compare the speeds of the plastic
and the steel marble
Movement Around the Loop
 The force that causes an object to move
in a circle is called a centripetal force
 Any type of physical force can be a
centripetal force if it results in circular
motion
 The centripetal force is
always directed toward
the center of the circle
that the object’s motion
follows
Centripetal Force
Consider Three Cases
Case number 1: If the weight is greater than
the required centripetal force, the ball moves
in a tighter circle. The tighter circle takes the
ball off the track and it does not catch cleanly.
Case number 2: If the weight is exactly equal
to the required centripetal force, the ball
follows the track perfectly and catches cleanly
in the catcher.
Case number 3: If the weight is less than the
required centripetal force, the ball would
move in a larger circle than the track if it
could. Instead, the track restrains the ball by
exerting a normal force back on the ball,
forcing it to follow the circle of the track
tightly and the ball catches cleanly in the
catcher.
What determines if the
marble makes it around?
 The weight must be less than or
equal to the centripetal force
required to make the ball go all
the way around
Using the Formula
 Challenge – Calculate the minimum
speed required for the marble to
stay on the track
 What happens to mass (m) in the
equation?
Mass
 Step 1- Divide both
sides of the equation
by the mass
 Mass does not seem
to be important
 Does this match our
observations?
Radius
 Step 2- Multiply both
sides of the equation
by the radius
 Take the square root
of both sides
 The velocity depends
on the radius
Using the Formula…Again
 The radius of the
loop is 10 cm, or
.1 meters.
 Use 9.8 m/sec2
for g
Compare
Calculations With
Observation
 How does this speed compare to what you
observed about the minimum speed required?
 What is the % error of your observed minimum
and our calculated minimum speed?
 What could account for this difference?
Clothoid Loop
 What is different about this shape?
 How would this
affect the
Centripetal force
of the coaster?
(Hint-think about
the radius of the
loop)
 Why would this be
useful?