## Reflection: Checks for Understanding Playing "A-Round" with Circular Motion - Section 4: Circular Motion Activity Debrief and Lecture

The variety of student answers to the questions are amazing. Students put in things such as gravity or friction being the cause of circular motion for the mable on the plate. My response to an incorrect answer is, "if I removed that force, would the marble not go in a circle?"  I lead students to the correct answer of the normal force through a process of elimination.

For many of the common mistakes on the sheets, I am able to catch during the activity itself. However, looking at Student Work - Circular Motion Activity, we can see that a few still remain. For instance, question two asks students what direction the force is in. In this case, I am looking for "inward" or "toward the center". On future sheets, I will give choices so that we can avoid answers like up or left.

Also worth carefully correcting with the students is the velocity vector. Many students like to draw a curved arrow that shows the path of the object. It is important to communicate that the vectors must be straight lines and that they show the velocity at a particular moment. A strategy I like to use is called, "my favorite no" where I show an incorrect answer such as the curved arrows on the second Student Work - Circular Motion Activity example. This answer makes a lot of sense to many students as it does show the path of the ball. But if we discuss what happens to the ball when the centripetal force is removed, it makes more sense to them that the velocity vector must be straight and tangent to the circle at that point.

Checks for Understanding: Reflection on Student Work

# Playing "A-Round" with Circular Motion

Unit 2: Forces in Two Dimensions
Lesson 6 of 16

## Big Idea: Uniform circular motion on an object happens when there is a net force acting towards the center of the circle.

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Standards:
Subject(s):
Circular Motion, Science, Physical Science, Newton's Laws, centripetal force, physics, Forces
50 minutes

### Jameson Parker

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