Interview Protocol

**Consent**: Hello! Thank you for agreeing to be interviewed today. Today I will be asking you about some common physics problems introductory students are asked. Before I explain the procedure of the interview, do you consent to being video recorded for the duration of this interview?

**Introduction**: Thank you! We will be video recording though out the interview. I’m also going to ask you to use this pen during the interview. It has a microphone in it to better pick up your voice and it will record everything you write down. As I said, I will be asking you about some common introductory physics problems. I’m particularly interested in how your initial “gut” response compares to your final answer. Because of this, there will be a timed portion and untimed portion of the interview. During the time portion, I will give you 4 problems to answer. You will have 30 seconds to answer each problem. I will also ask you to rate how certain you are of your answer on a scale of 1 to 7: 1 being “guessing” and 7 being “absolutely certain”. After you have completed all 4 problems, I will then ask you about each problem individually. During this portion of the interview, you will have as much time as you like to work through the problems. I ask that you talk through your thought process, like a “think-a-loud”, during this portion of the interview. Do you have any questions before we begin? [If they do have questions, just keep following up with “Anything else?” until they say no.]

**Timed Portion:** Great! Let’s begin. As I said, I will be giving you 30 seconds to answer each problem and rate how certain you are of that answer on the scale below the problem. Once all 4 questions are done, we will continue to the untimed portion of the interview. I do not need you to think-aloud for this portion. Are you ready to begin? [Give the questions individually so the interviewee cannot move on to without completing the previous question. Plan for the interviewee to use all 30 seconds but if they finish early it’s okay to continue. Give both screening questions then both target questions.]

**Questions (in order given)**

**Untimed Portion**

[Before the untimed portion look at the confidence levels of each questions. If they are all within +-1 of each other, ask the questions in the order the interviewee answered them. If not, ask about questions in the order of rising confidence.]

First questions for all problems: Can you tell me what you think the question is asking in your own words?

Second question for all problems: Now that you have more time to think about the question. Can you spend some more time thinking about the question? Please think aloud. It’s okay to change your answer if you want just to talk through your thought process. [All other questions are specific to the given problem.]

**Magnet Screening-Target**

Screening:

- Can you explain
your reasoning for your (initial) answer?
- [If the interviewee changed their answer:] Can you explain your reasoning for your final answer?

- [If they answer
but don’t mention Newton’s 2
^{nd}law. If they do, skip to 2a-c.] What physics principles did you use to come to your answer?- [If they don’t
mention what forces they consider for Newton’s 2
^{nd}law.] Can you talk about how you used Newton’s 2^{nd}law? What forces were you thinking about?

- [If they don’t mention how forces impact motion but mention them summing to zero.] You mentioned that “__________” [use interviewee words about forces summing to zero]. Why is that important? What would happen if it weren’t true?

- [If they don’t mention how forces impact motion and don’t mention them summing to zero]. So, you mentioned all these forces. Can you talk about how they work?

- [If they don’t
mention what forces they consider for Newton’s 2
- [If they say not
enough information]. What information would you need to solve this problem?
- [If they mention normal force] Well, the question says the table pushes up with 30 N. With that, could you solve the problem?

- [If they mention weight] Well, the question says the block weight 50 N. With that, could you solve the problem?

Target:

- Can you explain your reasoning for your (initial) answer?
- [If the interviewee changed their answer:] Can you explain your reasoning for your final answer?

- [If they answer and don’t mention Newton’s 2
^{nd}law. If they do, skip to 2a-c.] What physics principles did you use to come to your answer?- [If they don’t mention what forces they consider for Newton’s 2
^{nd}law.] Can you talk about how you used Newton’s 2^{nd}law? What forces were you thinking about?

- [If they don’t mention how forces impact motion but mention them summing to zero.] You mentioned that “__________” [use interviewee words about forces summing to zero]. Why is that important? What would happen if it weren’t true?

- [If they don’t mention how forces impact motion and don’t mention them summing to zero]. So, you mentioned all these forces. Can you talk about how they work?

- [If they don’t mention what forces they consider for Newton’s 2
- [After they’ve mentioned the friction force.] So, you’ve mentioned “________” [use the interviewee’s words about friction]. Would you mind explaining what you know about friction? How does it work?
- [If they say friction points up.] Can you explain why you think friction points upward?

- [If they say friction points down.] Can you explain why you think friction points downward? (Slap 1)
- [If they don’t catch that friction should be pointing up.] Can you do Newton’s 2
^{nd}law explicitly for me? (Slap 2)

- [If they don’t catch that friction should be pointing up.] If the magnet is at rest, what should the sum of the forces be? What would that mean for the friction? (Slap 3)

- [If they don’t catch that friction should be pointing up.] Because the magnet is at rest, the sum of the forces should 0. What would this mean for the friction? (Slap 4)

- [If they don’t catch that friction should be pointing up.] Is there any situation where the friction could be pointing up? (Slap 5)
- [If they say yes.] Is it possible that the friction is pointing up in this situation?

- [If they say no.] What if I told you the friction is pointing upward? How would you reconcile that with Newton’s 2
^{nd}law? (Slap 6)

- [If they don’t catch that friction should be pointing up.] Can you do Newton’s 2

- [If they say not enough information] What information would you need to solve this problem?
- [If they mention weight]. Well the problem says the magnet weight 10 N. With that, could you answer the question?

- [If they mention force of the hand] Well the problem says the hand pushes with 6 N. With that, could you answer the question?

- [If they mention coefficient of friction] Is there any way to find the force of friction without the coefficient of friction?
- [If they say no] If the magnet is going to stay still, what does that mean about the forces? (Slap 1)

- [If they don’t get to Newton’s 2
^{nd}law] Could you use Newton’s 2^{nd}law to solve this problem? (Slap 2) (Go to Newton’s law protocol 2b)

**Incline Screening-Target**

Screening:

- [Ask this for both the normal and friction force. Ask 1(a), then 2, then 1(a), then 3.] Can you explain your reasoning for your (initial) (first/second) answer?
- [If the interviewee changed their answer:] Can you explain your reasoning for your final (first/second) answer?

- [For the normal force question: If they don’t mention Newton’s 2
^{nd}law. If they do, skip to 2a-c.] What physics principles did you use to come to your answer?- [If they don’t mention what forces they consider for Newton’s 2
^{nd}law.] Can you talk about how you used Newton’s 2^{nd}law? What forces were you thinking about? - [If they don’t mention how forces impact motion but mention them summing to zero in the y-direction.] You mentioned that “__________” [use interviewee words about forces summing to zero]. Why is that important? What would happen if it weren’t true?
- [If they don’t mention how forces impact motion and don’t mention them summing to zero in the y-direction]. So, you mentioned “_________” [use interviewee’s words about forces in y-direction]. Can you talk about how they work?

- [If they don’t mention what forces they consider for Newton’s 2
- [For the friction force questions: If they don’t mention the friction equation. If they do, skip to 3a-b.] What physics principles did you use to come to your answer?
- [If they say f
_{1}> f_{2}] Can you explain why the friction in Case 1 is greater than the friction in Case 2? - [IF they say f
_{1}= f_{2}] Can you explain why the friction is the same in both cases? (Slap 1)- [If they don’t catch that f
_{1}> f_{2}.] Can you compare the frictions explicitly for me? (Slap 2) - [If they don’t catch that f
_{1}> f_{2}.] According to the equation you wrote, friction depends on the normal force. How does the normal force change from Case 1 to Case 2? How does this impact friction? (Slap 3) - [If they don’t catch that f
_{1}> f_{2}.] The normal force decreases from Case 1 to Case 2. What does that mean for the friction forces? (Slap 4) - [If they don’t catch that f
_{1}> f_{2}.] Is there any way for the friction forces to not be equal? (Slap 5)- [If they say yes but focus on the surface.] Is there a way for the forces to be different without changing the box and surface?
- [If they say yes and focus on the normal force]. Is it possible that the friction forces are not equal in this situation?
- [If they say no.] What if I told you f
_{1}> f_{2}? How would you reconcile that with the friction equation? (Slap 6)

- [If they don’t catch that f

- [If they say f
- [If they say not enough information] What would you need to answer this question?
- [If they mention normal force] Well, even without the numerical values is there a way you can compare the normal forces?
- [If they mention coefficient of friction] Would the coefficient of friction matter here?
- [If they say yes] So, it’s the same box on the same surface. Would the coefficient of friction change?

Target:

- Can you explain your reasoning for your (initial) answer?
- [If the interviewee changed their answer:] Can you explain your reasoning for your final answer?

- [If they don’t mention the friction equation. If they do, skip to 2a-c.] What physics principles did you use to come to your answer?
- [If they say decreases]. Can you explain why the friction decreases as the angle increases?
- [If they say remains the same]. Can you explain why the friction remains the same as the angle increases? (Slap 1)
- [If they don’t catch that friction should decrease.] Can you compare the friction explicitly for me? (Slap 2)
- [If they don’t catch that friction should decrease.] According to the equation you wrote friction depends on the normal force. How does the normal force change as the angle increases? (Slap 3)
- [If they don’t catch that friction should decrease.] The normal force is decreasing as the angle increases. What does that mean for the friction force? (Slap 4)
- [If they don’t catch that friction should decrease.] Is there a way for the friction to not remain the same?
- [If they say yes but focus on the surface.] Is there a way for the forces to be different without changing the block and surface?
- [If they say yes and focus on the normal force]. Is it possible that the friction force does not remain the same as the angle increases then?
- [If they say no.] What if I told you the friction decrease as the angle increases? How would you reconcile that with the friction equation? (Slap 6)

- [If they say increases.] Can you explain why the friction increases as the angle increases? (Slap 1)
- [If they don’t catch that friction should decrease.] Can you compare the friction explicitly for me? (Slap 2)
- [If they don’t catch that friction should decrease.] According to the equation you wrote friction depends on the normal force. How does the normal force change as the angle increases? (Slap 3)
- [If they don’t catch that friction should decrease.] The normal force is decreasing as the angle increases. What does that mean for the friction force? (Slap 4)
- [If they don’t catch that friction should decrease.] Is there a way for the friction to not increase as the angle increases?
- [If they say yes but focus on the surface.] Is there a way for the forces to be different without changing the block and surface?
- [If they say yes and focus on the normal force]. Is it possible that the friction force does not remain the same as the angle increases then?
- [If they say no.] What if I told you the friction decrease as the angle increases? How would you reconcile that with the friction equation? (Slap 6)

- [If they say not enough information] What would you need to answer this question?
- [If they mention normal force] Well, even without the numerical values is there a way you can compare the normal forces?
- [If they mention coefficient of friction] Would the coefficient of friction matter here?
- [If they say yes] So, it’s the same box on the same surface. Would the coefficient of friction change?