8.4: Procedures
- Page ID
- 29159
You will analyze three systems involving circular motion.
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Draw a table in which to record your circular motion data and observations. Do not fill in data until you have read the instructions for obtaining that data.
System |
Mass (grams) |
Radius of Path (centimeters) |
Centripetal Force |
Push or Pull |
Centripetal Force Direction |
---|---|---|---|---|---|
Marble & Pie Tin |
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Ball & Rope |
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Spaceship & Earth |
Marble around the Pie Tin
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Predict the path the marble will take as it leaves the opening in the pie tin. Will it continue in a circular path or will it travel in a straight line when it leaves the pie tin? Describe or sketch your prediction.
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Place the pie tin on the table, and start the marble traveling along the inside edge of the pie tin. You will need to give the marble a good, fast start with your hand; the pie tin should remain on the table for this. Describe or sketch the path of the marble after it leaves the pie tin through the opening.

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Name or describe the centripetal force that kept the marble traveling in a circle while it was in the pie tin. Record whether the marble was pushed or pulled into a circular path, and the direction of the push or pull that kept the marble circling while it was in the pie tin.
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Measure the mass of the marble, and the radius of the pie tin. Enter these values in your data table.
Orbiting Object
Warnings
- Be careful that no one is impacted by your orbiting object, and do not let go of it.
- Impact safety glasses are recommended while circling the object on the rope.
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Predict whether it will be more difficult to hold onto the rope when the object is circling with a slow or fast speed. Record your prediction.
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Hold the rope firmly and circle the object at a steady rate. Then increase the speed at which your object is circling. In which case is more force required to hold onto the circling object, when it has a slow orbital speed or a fast orbital speed? Record your answer.

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Name or describe the centripetal force that kept the object on the rope traveling in a circle. Record whether the object on the rope was pushed or pulled into a circular path, and the direction of the push or pull that kept the ball and rope circling.
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Measure mass of the object and rope, and the radius of the system (length of the rope). Enter the mass and radius values in your data table.
Space Ship
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A spaceship is in orbit 300 km above the surface of the Earth (r = 6.378 x 106 meters). Assume the spaceship is the USS Enterprise from Star Trek, with a mass of 9.6 x 107 kg. Record the mass of the ship and the radius of the orbit in your data table.


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Name or describe centripetal force that keeps the spaceship orbiting the Earth. Record whether the ship is pushed or pulled into a circular path, and the direction of the push or pull that keeps the ship circling.