Investigating Rotational Inertial Using Tops
Summary
In this inquiry or guided inquiry (depending on grade level) investigation, students will examine factors affecting rotational inertia. Students will keep a science journal of their investigation.
Learning Goals
Students will develop testable questions related to rotational inertia. The students will identify the factors involved in rotational inertia. This activity will develop thinking skills, inquiry skills regarding rotational inertia, and enhance their understanding of the scientific method in determining their outcomes. Students will then share their findings with the rest of the class and formulate a hypothesis on conditions affecting rotational inertia.
Vocabulary:
Cause and effect
Variables
Controlled variables
Rotational motion
Rotational inertia
Mass
Hypothesis
Vocabulary:
Cause and effect
Variables
Controlled variables
Rotational motion
Rotational inertia
Mass
Hypothesis
Context for Use
This is a hands-on, lab lesson to be used in a classroom setting (grades 9-12)
The "hands-on" part of the investigation will be completed in 2-3 days of 20-30 minute class times. This investigation can be teacher-demonstrated entirely, OR all student-performed, OR a combination of both depending on supplies available, time allotted, and grade level. Discussion prior to this activity on rotational inertia can take place, or it can be a discovery activity. Some time is needed to comprise testable questions regarding rotational inertia and additional time to perform each aspect of the investigations. A final day is needed to "wind up" the discussion and to come up with a hypothesis regarding each factor that affects rotational inertia.
No special equipment is needed other than the supplies listed.
The "hands-on" part of the investigation will be completed in 2-3 days of 20-30 minute class times. This investigation can be teacher-demonstrated entirely, OR all student-performed, OR a combination of both depending on supplies available, time allotted, and grade level. Discussion prior to this activity on rotational inertia can take place, or it can be a discovery activity. Some time is needed to comprise testable questions regarding rotational inertia and additional time to perform each aspect of the investigations. A final day is needed to "wind up" the discussion and to come up with a hypothesis regarding each factor that affects rotational inertia.
No special equipment is needed other than the supplies listed.
Description and Teaching Materials
This activity is adapted from Teaching Physics with Toys, Beverley A.P. Taylor, Dwight J. Portman, Susan Gertz, Lynn Hogue, Miami University, Terrific Science Press, 2005
Items needed:
Paperboard (enough for an 8-cm disk per group)
* Cereal box cardboard can be used instead
Scissors
Compass (optional)
Protractor (optional)
Parts A and B, per group:
Pencil (hexagonal) (about 10-12 cm long) with a blunt point
Piece of paper
8-cm prepared disk
Ruler
2 small rubber bands
Stopwatch
6 small paper clips
6 pennies
Tape or glue stick
Part C, per group:
Small tops or material to make a top
Assorted pencils, cardboard, poster board, unwanted CDs, tape, pennies,
paper clips, washers, and small rubber bands
Ruler
Stopwatch
Scissors (optional)
For the Assessment, per group:
2 sticks
Paperboard/Cardboard (enough to make 2 disks)
4 small rubber bands
12 washers with hole large enough to fit the sticks through
Begin investigation with a discussion on what rotational inertia is and what factors (things) could affect it. How could we test these "things". (Students, hopefully, will come up with factors like mass and location. This can be teacher guided or not. Have several tops to demonstrate their spin and discuss the factors and attributes of each top and how it spins.
Make a template of an 8 cm diameter round disk for students to copy or older students can make their own as follows:
Use compass and protractors to make an 8 cm disk with marked divisions every 60 degrees.
Poke a small starter hole, approximately 2 mm in diameter, in the center of each circle.
Procedure:
Part A
1. Put the point of a pencil down on the table or floor and spin it like a top (paper under the pencil will prevent marks).
Observe what happens. (Discuss what would help the pencil to spin better and longer).
2. Make a top by poking the pencil through the starter hole in the paperboard disk without tearing the hole any bigger than necessary. The disk should sit about 2.5 cm above the tip of the pencil. Prevent the disk from sliding by putting a rubber band around the pencil below the disk and another around the pencil above the disk.
3. Spin the top by twirling the pencil with your fingers. Practice until you get the top to spin on most tries.
(Discuss the difference in spinning between #1 and #3)
Make a chart and record the spin time (before the disk touches)
Do this 9 times (count only legitimate spins) and record the tries and an average.
Part B: Does Mass Matter?
Discuss what would happen if you added mass to the disk and then spun
the top.
1. Add six paper clips at the 60 degree pencil marks on the disk.
2. Spin the top 9 times and record the tries and the average on the chart.
(Discuss which top (with or without paperclips) has the longer spin
time and which took more push from your fingers.
3. Remove the paperclips and hold them in one hand with 6 pennies in the
other hand. Which has the greater mass?
(Discuss which would have a greater effect on the spin and why)
4. Tape or glue the six pennies on the disk at the 60 degree marks.
5. Measure the spin time of the top nine times and average. Record your
results on the chart.
(Discuss which needs a bigger push from you fingers to start
spinning, the top with the pennies or the paper clips. Which has a
longer spin time? How does mass affect the spin?)
Part C: Design your own top.
1. Try moving the disk to three different heights from the tip of the pencil and note the results.
2. Try 3 different disk diameters. What are the results? Is there a pattern?
Assessment:
Make two identical pencil and disk tops. On one stack 6 washers over the pencil on top of the disk. On the other place six washers around the disk perimeter. Make a prediction as to which top will average the longest spin time. Record your answer before you actually attempt the spins. Explain your answer/prediction. Spin the tops three times and record the results and the average. Which has the longest/shortest spin time? How does your results match you prediction. Explain any differences.
Prior to each of these activities solicit questions and or answers for what is about
to happen.
After each activity, solicit reasons for the behavior of the materials and encourage
additional questions regarding what has happened.
Closure/Evaluation:
Discuss the results of the investigation and students can write their own conclusions to the investigation in their science journals.
Items needed:
Paperboard (enough for an 8-cm disk per group)
* Cereal box cardboard can be used instead
Scissors
Compass (optional)
Protractor (optional)
Parts A and B, per group:
Pencil (hexagonal) (about 10-12 cm long) with a blunt point
Piece of paper
8-cm prepared disk
Ruler
2 small rubber bands
Stopwatch
6 small paper clips
6 pennies
Tape or glue stick
Part C, per group:
Small tops or material to make a top
Assorted pencils, cardboard, poster board, unwanted CDs, tape, pennies,
paper clips, washers, and small rubber bands
Ruler
Stopwatch
Scissors (optional)
For the Assessment, per group:
2 sticks
Paperboard/Cardboard (enough to make 2 disks)
4 small rubber bands
12 washers with hole large enough to fit the sticks through
Begin investigation with a discussion on what rotational inertia is and what factors (things) could affect it. How could we test these "things". (Students, hopefully, will come up with factors like mass and location. This can be teacher guided or not. Have several tops to demonstrate their spin and discuss the factors and attributes of each top and how it spins.
Make a template of an 8 cm diameter round disk for students to copy or older students can make their own as follows:
Use compass and protractors to make an 8 cm disk with marked divisions every 60 degrees.
Poke a small starter hole, approximately 2 mm in diameter, in the center of each circle.
Procedure:
Part A
1. Put the point of a pencil down on the table or floor and spin it like a top (paper under the pencil will prevent marks).
Observe what happens. (Discuss what would help the pencil to spin better and longer).
2. Make a top by poking the pencil through the starter hole in the paperboard disk without tearing the hole any bigger than necessary. The disk should sit about 2.5 cm above the tip of the pencil. Prevent the disk from sliding by putting a rubber band around the pencil below the disk and another around the pencil above the disk.
3. Spin the top by twirling the pencil with your fingers. Practice until you get the top to spin on most tries.
(Discuss the difference in spinning between #1 and #3)
Make a chart and record the spin time (before the disk touches)
Do this 9 times (count only legitimate spins) and record the tries and an average.
Part B: Does Mass Matter?
Discuss what would happen if you added mass to the disk and then spun
the top.
1. Add six paper clips at the 60 degree pencil marks on the disk.
2. Spin the top 9 times and record the tries and the average on the chart.
(Discuss which top (with or without paperclips) has the longer spin
time and which took more push from your fingers.
3. Remove the paperclips and hold them in one hand with 6 pennies in the
other hand. Which has the greater mass?
(Discuss which would have a greater effect on the spin and why)
4. Tape or glue the six pennies on the disk at the 60 degree marks.
5. Measure the spin time of the top nine times and average. Record your
results on the chart.
(Discuss which needs a bigger push from you fingers to start
spinning, the top with the pennies or the paper clips. Which has a
longer spin time? How does mass affect the spin?)
Part C: Design your own top.
1. Try moving the disk to three different heights from the tip of the pencil and note the results.
2. Try 3 different disk diameters. What are the results? Is there a pattern?
Assessment:
Make two identical pencil and disk tops. On one stack 6 washers over the pencil on top of the disk. On the other place six washers around the disk perimeter. Make a prediction as to which top will average the longest spin time. Record your answer before you actually attempt the spins. Explain your answer/prediction. Spin the tops three times and record the results and the average. Which has the longest/shortest spin time? How does your results match you prediction. Explain any differences.
Prior to each of these activities solicit questions and or answers for what is about
to happen.
After each activity, solicit reasons for the behavior of the materials and encourage
additional questions regarding what has happened.
Closure/Evaluation:
Discuss the results of the investigation and students can write their own conclusions to the investigation in their science journals.
Teaching Notes and Tips
This activity can be done in groups or teacher demonstrated. If done in groups (which I like better), each group can report on things they "discovered" in their investigation. Also, they can discuss what additional investigations/questions they thought of. The students in one group can meet with other groups to compare their findings.
If you want to speed up the investigation, groups can be assigned different aspects of the investigation and then share their results and conclusions. These conclusions then can then be evaluated by the other groups and discussed.
Some prior discussion on inertia and specifically rotational inertia can and should take place.
In the past, I have lectured about the aspects of rotational inertia. I have demonstrated tops before, but I have not done a lab regarding it. Most of the questions I have received regarding the concept of rotational inertia are investigated in this activity. In this exercise, students will receive first-hand experience with the factors involved in rotational inertia. I do not expect any unusual problems to arise.
If you want to speed up the investigation, groups can be assigned different aspects of the investigation and then share their results and conclusions. These conclusions then can then be evaluated by the other groups and discussed.
Some prior discussion on inertia and specifically rotational inertia can and should take place.
In the past, I have lectured about the aspects of rotational inertia. I have demonstrated tops before, but I have not done a lab regarding it. Most of the questions I have received regarding the concept of rotational inertia are investigated in this activity. In this exercise, students will receive first-hand experience with the factors involved in rotational inertia. I do not expect any unusual problems to arise.
Assessment
* Teacher observation of students participation in discussions, and questioning
activities.
* Students ability to write inquiring questions in their journal and then plan how
they will answer their questions.
* Students will hand in a worksheet (table) regarding various investigations of
rotational inertia and the factors affecting it.
* Informally assessing how student work in groups and interact with each other.
* Reviewing the results of their predictions regarding their assessment tops.
activities.
* Students ability to write inquiring questions in their journal and then plan how
they will answer their questions.
* Students will hand in a worksheet (table) regarding various investigations of
rotational inertia and the factors affecting it.
* Informally assessing how student work in groups and interact with each other.
* Reviewing the results of their predictions regarding their assessment tops.
Standards
9-12 I.B.1
9-12 I.B.2
9-12 II.E.2
9-12 I.B.2
9-12 II.E.2