# 3 October Science 7 Acceleration; “All motion is relative”–what does that mean?

1. Mindful moment.
2. Review previous DSN. (We previewed trees–to get ready for WOW and to start longterm observation. We have more to learn about motion and energy this semester, so we will continue with that topic, too.)
3. Preview today’s blogpost.
4. Create DSN entry for today.
5. Questions.
• * * * *

A. Make a new group of 3. These should be students you have not worked with before (or have worked with the fewest number of times). Update your collaboration chart / document. Names, topics, activities, dates, links (relevant blogposts, DSN entries, group documents and data)

You will receive a pullback car. Explore its operation. Do not overstretch the spring, but do find the point that gives maximum acceleration and distance. Do a trial run without measuring. Each student separately make a sketch graph (distance vs. time) of how you think the motion would look. Discuss with your group your ideas using your sketch graph to illustrate your point. Make sure you have a rich entry for the section “what we talked about” in your DSN entry.

Design a track (frame of reference) to evaluate how the speed changes. This will be very similar to your tumble buggy procedure. Find the times to reach various distances. Make a distance vs. time graph to display your results. Calculate the average speed for zero meters to the maximum distance you measure. Can you find average speeds for other segments, like from 0-1, 1-2, and 2-3? Be prepared to share your findings with the rest of the class.

***All students: Reply to today’s blogpost. Describe how you think the pullback car works. What  do you think makes the car changes its speed from 0 m/s to the other speeds you observe during a trip? What is the mechanism do you think? Make a sketch of your imagined mechanism and add link to blog–with sharing so that anyone with the link can view. Be sure the response that you submit on the blog is also copied into your DSN entry for the day.

Reply to another student’s comment. Ask a clarifying question about their sketch and the mechanism they have proposed.

B. Thought problem. Answer with a sketch graph (distance vs. time) and description. If a cart is pulled with a constant force, what motion do you think will result?

C. We shall watch and discuss in detail the motion examples presented in: Frames of Reference < https://www.youtube.com/watch?v=bJMYoj4hHqU >. What is your understanding of the statement, “All motion is relative?” If we do not have time to watch this as a class, watch on your own. Have your questions ready. Be prepared for a quiz in an upcoming class.