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).
  • 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.