No captions Captions Stop the video above first if it is playing.
No captions Captions Stop the video above first if it is playing.
Mary and Claire revisit their thinking from the first episode. They consider what else you would need to know to determine the angle of rotation, if you know that length of the arc the object traces out while traveling along a circular path.
Episode Supports
Students’ Conceptual Challenges
Mary claims that you need to know both the circumference and the radius of the circle in order to find the angle of rotation, given an arc length [1:15]. However, knowing only one of those pieces of information is sufficient. Check with your students to see if they think similarly as Mary, and if so, encourage them to talk about why they would need both the radius and the circumference. Look for opportunities for students to share why knowing only either the radius or the circumference is sufficient.
Focus Questions
For use in a classroom, pause the video and ask this question:
[Pause the video at 1:30] What do you think Claire means when she says you’d have to find the fraction of the arc compared to the rest of the circumference? How would that help you find the angle of rotation?
Supporting Dialogue
[Pause the video at 1:45] Mary has claimed that you need to know both the circumference and the radius of the circle in order to find the angle of rotation, given an arc length. Talk with a partner about this – do you agree or disagree? Explain your reasoning.
Captions
