Foundations of Physical Science

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Foundations of Physical Science - PowerPoint PPT 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?. www.rcdb.com. Roller Coasters. The CPO Loop Track. Investigate Motion of Marble.

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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?
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?
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?
• 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 acentripetal force if it results in circular motion
• The centripetal forceis always directed toward the center of the circle that the object’s motion follows
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?
• 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