##
* *Reflection: Checks for Understanding
Mass vs. Weight - Section 2: Free Body Diagram Rally Coach

As I graded these rally coach activities, I found that a lot of students had one minor mistake on their free body diagrams and that in turn made all of the answers to their questions wrong. Their mistake was not having the normal force perpendicular to the surface which caused them not to note that friction and part of the normal force would cancel out and the weight and part of the normal force would cancel out, providing a state of equilibrium and not net force. I think that it was an eye-opener to students because they were able to see what happens when they are not careful in reading the situation, as seen in these student examples (Rally Coach Student Work, Rally Coach Student Work (2)).

*Checks for Understanding: All or Nothing*

# Mass vs. Weight

Lesson 6 of 9

## Objective: Students will be able to identify the difference between mass and weight and will be able to convert between mass and weight.

*70 minutes*

#### Carousel Whiteboard Session

*20 min*

The goal of this lesson is to finish up on free body diagrams and to differentiate between mass and weight. Students will use the models of free body diagrams as well as mathematical and computational thinking. To start off class, I ask students to take out their packets and open them to Worksheet #2 Free Body Diagrams that they finished for homework from the previous lesson.

To go over Worksheet #2, I have the students work together with their tables to create a whiteboard for a problem on the worksheet. To assign the problems on the worksheet, I ask one student from each table to pick a playing card that I have picked out to represent each problem. When all of the problems are taken there is one remaining that I will complete. I give students about 3-4 minutes to create their whiteboards. The whiteboards turn out like this (WS #2 Whiteboard, WS #2 Whiteboard (2), WS#2 Whiteboard (3)).

When they are done with their whiteboards, I have them set up the whiteboards around the room so that they can do a carousel with the whiteboards. During the carousel, I give students 1 minute at each whiteboard to check their answers and write a question on their page if they don't agree. Once the students have made it to every whiteboard, I ask if there are any questions on problems #1-3, then #4-6, then #7-9 and we address and concerns students have or mistakes groups made on their whiteboards. I use the carousel to review the problems because it gives students time to process on their own by checking their work with what other students have done as well as time to create a question to ask if they don't agree with the whiteboard. After they are done students are able to ask questions about ones they don't agree with or don't understand.

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When students have returned to their seats after the whiteboard carousel, I ask them to work with the person sitting next to them to complete the FBD Rally Coach. To complete the rally coach activity, each partner writes his or her name on the top of one column and completes the problems in that column. When that student finishes, the partner checks his or her work before they switch roles on the next column. I do this activity toward the end of the free body diagram activities because students should have enough experience with the material that it should be quick. This activity also holds students accountable to each other since they both receive the same grade. To grade this activity, I give 5 points for each problem: 2 for the free body diagram and 3 points for the questions.

#### Resources

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#### End of Discussion Checkpoint

*10 min*

After students complete the rally coach activity, I ask them to put everything away for an End of Discussion Checkpoint #2. This is a formative assessment to show me how much they understand about how to create free body diagrams. There are three questions and I try to make 2 at an average level, meaning similar situations to what we have experienced, and one at a little higher level, meaning a situation they have not yet seen anything like it before, to stretch some students. You can see the results of the students in EOD #2 Student Work. At this point in the unit students have had ample practice drawing and analyzing free body diagrams through 2 worksheets, an exit slip and the rally coach activity so they should be able to complete these on their own.

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#### Mass vs. Weight Guided Notes

*10 min*

After all of the students have turned in their end of discussion checkpoints, I ask them to turn to their Mass v Weight Guided Notes. They have previously read about mass and weight during their guided reading activity at the beginning of the unit. Since they have a little bit of knowledge about mass and weight, I ask them to name characteristics of mass or weight to put on the graphic organizer. We complete this as a whole class activity with my notes on the board as a reference for students of our discussion. As we list different characteristics, I make sure to keep the similar characteristics in the same horizontal line so that the students can see the relationships more easily, as shown in Mass vs. Weight Notes. We discuss ideas like dependance on location, units, and definitions. I like to use the graphic organizer, especially for some of my visual learners, to help student have a picture of how mass and weight are different.

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After students have learned the properties of mass and weight and the equation (Weight = mass x acceleration due to gravity) they can use to convert between mass and weight, I ask students to complete the Mass vs. Weight worksheet (Concept Development Practice Page 3-1 from the Conceptual Physics textbook). I allow students to work with their table groups and use the remaining class time to finish the worksheet. I like to use this worksheet because it helps students to recall what they just learned about the major differences between mass and weight. I also like that it gives students some practice with converting between mass and weight. Students work on this worksheet with their groups until the end of the period and we go over it as a class in the next lesson.

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- LESSON 1: Intro to Newton's First Law of Motion
- LESSON 2: Inertia Day
- LESSON 3: Inertia Demo Day
- LESSON 4: Free Body Diagram, Day #1
- LESSON 5: Free Body Diagrams, Day #2
- LESSON 6: Mass vs. Weight
- LESSON 7: Newton's 3rd Law, Day 1
- LESSON 8: Newton's 3rd Law, Day 2
- LESSON 9: Unit 4 Test: Inertia and Interactions