Physics I: Class Structure, In-Class Assignments, and Average Speed vs Velocity

Course Logistics and Grading

• The course includes three tests and a final exam.
• In-class assignments are worth 20% of the final course grade.
• The final exam contributes to the final grade (the transcript mentions a 30% final grade component, implying the final exam weight is part of the total). The exact breakdown is listed in the syllabus.
• The syllabus and dates for the three tests are posted on Canvas under course resources.
• The dates for tests are specified in the syllabus and Canvas resources; students should refer there for exact dates.
• The instructor emphasizes that the final grade is not based on attendance; it is based on performance and effort on assigned problems.

In-Class Participation and Problem Solving Expectations

• Reasonable attempt to solve each problem shown in class is part of the grade; getting the right answer is indicative but not the sole measure.
• Not getting the right answer is not necessarily a failure if students make honest effort and learn from the attempt.
• A student’s participation is about engagement and effort, not merely being present while others struggle.
• The class philosophy: understanding science benefits everyone; helping peers understand the material improves overall learning.
• Students are encouraged to explain their reasoning on whiteboards, not just present final answers.

In-Class Assignments: Process and Submission via Gradescope

• For in-class assignments, groups will work on whiteboards during class.
• Students should take pictures of their whiteboard work to Gradescope, showing both the problem-solving process and the final answer when possible.
• If a problem isn’t finished, students should upload what they did, including partial solutions.
• Initially, this was a group assignment, but in the near term, students may upload their own versions (each student uploads their own photo).
• The deadline for submission is around noon or midnight (the exact time is stated in the course platform).
• Students are encouraged to discuss and compare solutions, ensuring that everyone understands the method, not just the final result.
• There is guidance on how to structure the submission: have one person perform calculations, others record the results on the whiteboard, and then upload the image(s).
• Sharing pictures after class is acceptable and encouraged; late submissions are allowed with no penalty for lack of finish on the day.
• The goal is to capture the reasoning and approach, not merely the final numerical answer.

Canvas, Gradescope, and Technology for Assessments

• The Gradescope link is accessible through Canvas, under Gradescope for the course.
• Each problem on Gradescope may have multiple parts (e.g., question 1, question 2); students should show the steps and reasoning.
• For group work, the plan is to have each student upload their own version of the work, at least initially, to clearly attribute contributions.
• If there are issues with group assignments or group membership, students should follow up with the instructor for clarifications.

Example Problem Discussion: Average Speed vs Velocity in a Circular Orbit

• Scenario: Earth is treated as moving in a circular orbit around the Sun with radius r = 1 AU (astronomical unit).
• Distance traveled in one complete orbit (one year):
  • The circumference of a circle: $C = 2\pi r$
  • With r = 1 AU, the distance traveled in one year is $D = 2\pi \times 1\text{ AU} = 2\pi\ \text{AU}$
• Time interval for one orbit: one year, so $\Delta t = 1\ \text{yr}$
• Average speed over the year:
  • Definition: $v_{\text{avg}} = \frac{D}{\Delta t}$
  • Substitution: $v_{\text{avg}} = \frac{2\pi\ \text{AU}}{1\ \text{yr}}$
• Average velocity over the year:
  • Definition: $\vec{v}_{\text{avg}} = \frac{\Delta \vec{r}}{\Delta t}$
  • After one complete orbit, the net displacement is zero: $\Delta \vec{r} = 0$
  • Therefore, $\vec{v}_{\text{avg}} = \frac{0}{1\ \text{yr}} = 0$ (magnitude 0, direction undefined for a closed loop over the full period)
• Distinguishing distance vs displacement:
  • Distance is the total path length traveled along the orbit: $D = 2\pi r = 2\pi\ \text{AU}$
  • Displacement is the straight-line vector from start to end point: for one full orbit, displacement is zero: $|\Delta \vec{r}| = 0$
• Important symbols:
  • Distance: typically denoted as D (a scalar)
  • Displacement: vector quantity, denoted as $\Delta \vec{r}$ or sometimes $\Delta x$ (scalar form is used in some contexts)
  • Time interval: $\Delta t$
  • Radius: $r$; in this example, $r = \text{AU}$
• Units and definitions:
  • An astronomical unit (AU) is a unit of distance defined as the average distance from the Earth to the Sun.
  • You can keep the units symbolic (AU and yr) for the sake of the problem, or convert to meters and seconds if needed.
• Key takeaway:
  • For a closed circular orbit over one full period, the average speed is nonzero (distance/time), but the average velocity is zero (net displacement over the period).
• Concept connections:
  • Demonstrates the difference between scalar distance and vector displacement.
  • Illustrates the definitions of average speed and average velocity in a real-world context (orbital motion).

Foundational and Conceptual Links

• Distance vs displacement: Distance is a scalar that accumulates along a path; displacement is a vector that depends only on the initial and final positions.
• Average speed vs average velocity: speed uses total distance over total time; velocity uses net displacement over total time.
• In circular motion, end position after one full loop equals the start position, so displacement is zero, but the object has traveled a finite distance along the path.
• The example reinforces the idea that understanding vectors and scalars is essential for kinematics.

Practical and Ethical Implications inLearning

• Collaboration: Working on in-class problems with peers supports collective understanding; however, all students are encouraged to demonstrate their own reasoning clearly when submitting work.
• Transparency: Uploading the reasoning process (not just the final answer) helps instructors assess conceptual understanding.
• Accessibility: Using digital tools (whiteboards, photos, Gradescope) requires students to be proficient with the platforms and mindful of deadlines.
• Growth mindset: The instructor emphasizes that struggle is part of learning and that low-stakes practice helps prepare for high-stakes tests.

Quick Reference: Notation and Formulas

• Distance traveled (circular path): $D = 2\pi r$
• Circumference for a circle with radius r: $C = 2\pi r$
• In our Earth example: $r = 1\ \text{AU}$, so $D = 2\pi\ \text{AU}$
• Time interval for one loop: $\Delta t = 1\ \text{yr}$
• Average speed: $v_{\text{avg}} = \frac{D}{\Delta t} = \frac{2\pi\ \text{AU}}{1\ \text{yr}}$
• Displacement after one full orbit: $\Delta \vec{r} = 0$
• Average velocity: $\vec{v}_{\text{avg}} = \frac{\Delta \vec{r}}{\Delta t} = 0$
• Distance vs Displacement: distance is path length; displacement is straight-line vector from start to end.

Notes on Language and Expression from the Session

• The instructor uses active, student-centered language to encourage engagement and understanding.
• The class emphasizes that the final grade reflects understanding and effort rather than mere attendance or the ability to memorize answers.
• The material highlights practical application of kinematics concepts to real-world contexts (orbital motion) and reinforces the separation between scalar and vector quantities.