Interactive Lecture Demonstration
Prediction Sheet—Rotational Motion
Directions:
Click here
to download the Prediction sheet. Write your name at the top to
record your presence and participation in these demonstrations. For
each demonstration below, write your prediction on this sheet before making any
observations. You may be asked to send this sheet to your instructor.
Only after you have made
your predictions, open the simulation Ladybug Revolution: https://phet.colorado.edu/sims/cheerpj/rotation/latest/rotation.html?simulation=rotation Drag
the ladybug to the outside edge. Use the slider to set the Angular
Velocity to about 60 rad/s. Observe the velocity and acceleration as the bug
passes through position 1 and position 2. Compare the two velocities to your predictions and
explain any differences. What is the direction of the acceleration relative
to the center of the disk? Click
here to see the vector subtraction. Compare the result
to your prediction. Describe the direction of the vector relative to the center of the disk. How does this
compare to the direction of the acceleration? Explain why. |
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Demonstration 2: For the motion of the turntable
described in Demonstration 1, sketch on the diagram on the right the net
force acting on the object at the edge of the turntable when it is at
position 1. What is the cause of this force? Only after you have made your prediction, click here to view the force. Compare the force to your prediction,
and explain why the force must be in this direction to cause the described
motion. |
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Only after you have made your predictions click here to see the two velocity vectors and the vector subtraction. Compare the two velocities to your predictions and explain any differences. Describe
the direction of the vector relative to the center of the turntable. Now use the same Ladybug Revolution
simulation. The ladybug should be on
the edge of the turntable in position 1. Place the cursor on the left edge of
the turntable, quickly rotate the turntable counterclockwise, and observe the
direction of the acceleration as the ladybug is accelerating towards position
2. Describe the direction of a and compare it to the direction of Explain what you observe. |
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Demonstration 4: For the motion of the disk
described in Demonstration 3, sketch on the diagram on the right the net
force acting on the object at the edge of the turntable when it is at
position 1. What is the cause of this force? Only after you have made your prediction, click here to view the force. Compare the force to your prediction,
and explain why the force must be in this direction to cause the described
motion. |
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Only after you have made your predictions click here to see the two velocity vectors and the vector subtraction. Compare the two velocities to your predictions and explain any differences. Describe the direction of the vector relative to the center of the turntable. Now use the same Ladybug
Revolution simulation. The ladybug
should be on the edge of the turntable in position 1. Place the cursor on the
left edge of the turntable, start rotating the turntable counterclockwise,
and observe the direction of the acceleration as you slow the turntable.
Be sure that you are observing a at a moment when it is slowing down. Describe
the direction of a and compare it to the direction of Explain what you observe. |
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Demonstration 6: For the motion of the disk
described in Demonstration 5, sketch on the diagram on the right the net
force acting on the object at the edge of the turntable when it is at
position 1. Only after you have made your prediction, click here to view the force. Compare the force to your prediction,
and explain why the force must be in this direction to cause the described
motion. |
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