Foundations of Physical Science

Foundations of Physical ScienceWorkshop: The Loop Track

The Loop TrackCPO Science

Key QuestionsWhy does a roller coaster stay on the track when it is upside down on a loop?

Roller Coasterswww.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?

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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 CasesCase 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?