Title:

Figure Skating and the Conservation of Angular Momentum

Grade Level:

6,7

Subject:

Science

Author:

nbclearn

Time:

55 minutes

Lesson Plan Type:

Video,Interactive Instruction

Keywords:

Figure Skating, Conservation of Angular Momentum, Rotational Speed, Centripetal Force

Brief Description:

Students will create an apparatus which will enable them to whirl a stopper on a string and while simultaneously reducing the radius of the circular motion. Using this apparatus, students will investigate concepts of conservation of angular momentum and centripetal force. Students will then describe and explain other situations, both in sports and elsewhere, where the conservation of angular momentum can be observed.

 

California State Standards Addressed:

Science/8/Focus on Physical Science)1.0,2.0

Related Links:

Link 1:
Link 2:

Goal(s):

Students will conduct a qualitative investigation of the relationship between the radius and the rotational speed of a stopper that is tied to a string and whirling in a circle. The students will make a hypothesis, conclusion, and present their findings to their peers. Through discussion, they will formalize an understanding of the conservation of angular momentum. They will apply the concepts they develop in this activity to other situations they have witnessed.

Specific Objectives:

Students will be able to:

1. Formulate a hypothesis.
2. Describe their investigation using words and pictures.
3. Record observations about the relationship between rotational speed and radius.
4. Interpret their observations to form a conclusion.

Required Materials:

Per group:
1 rubber stopper with hole (other soft/blunt object can be used if it there is a way to securely fasten them to a string), 4 feet of string or fishing line, the barrel/tube from a ball point pen, safety glasses for each student

Optional: Rotating office chair

Anticipatory Set (Lead-in):

Ask if any students have ever watched Olympic figure skating or Olympic diving. Ask if anyone can guess how these sports are similar to water swirling down into a bathtub drain. Discuss with them briefly that circular or rotational motion is involved in all these cases. Tell them that they are going to watch a short video on the science of figure skating and then do a short activity to learn some details about circular motion and angular momentum.

Lesson Plan Procedure:

Note: This lesson assumes prior knowledge of inertia and the conservation of momentum. If necessary, these should be briefly reviewed before the video.

1. Before showing the video, mention that in addition to learning about the science of figure skating, the students also will see in this video that it is possible to be an athlete and a scholar (the skater, Rachel Flatt, is also an AP Physics Student.)
2. Show students the NBC Learn Video: Figuring out Figure Skating
3. Hand out the activity “worksheet: Whirling Stopper”. Go over the task and the equipment. Clarify the terms radius of curvature and rotational speed.
4. Give students approximately 15 minutes to complete the activity and the worksheet questions 1-4. They can also do question 5 in class or for homework.
5. Ask students to share their answer to question 4, the relationship between radius of curvature and rotational speed.

Closure (Reflect Anticipatory Set):

If time and equipment permit, you can use a swiveling office chair to perform the same demonstration of angular momentum that was shown in the video. Also, you can ask a student to describe more specifically how this relates to diving, and specifically why do divers tuck?

Another closure option is to watch a slow motion video of a figure skating “quad” jump which involves four turns in one jump. The students can watch and clearly see the arms and legs go in to increase rotational speed and then go out to slow down the rotational speed upon landing.

Plan for Independent Practice:

Have student think of an example not discussed in class and answer question 5.

Assessment Based on Objectives:

The activity worksheet can be used as an assessment.

Possible Connections to Other Subjects:

Language Arts: Students can research and write about how the law of conservation of angular momentum helps explain rotations in the solar system.

Adaptations and Extensions:

Students can explore and write about the role of centripetal force in this experiment. They can also discuss the path the stopper would take if the string were to break.

Additional Notes:

Depending upon your curriculum and objectives, the relationship can be expressed in various forms: inversely related, indirectly related, inversely proportional, they react oppositely, etc.