# 29 October Science 7 Force and acceleration resumed; Newton’s Laws

Welcome back from WOW.

a. Mindful moment. Close your eyes and think of the most beautiful or calming sight you saw during WOW. Focus on that for a few minutes while you practice your mindful breathing.

b. Look back at your DSN for the last class entries devoted to motion.

c. Preview today’s blog post.

d. Prepare your DSN entries for today. We will do some writing about WOW first–some of that writing will go into in your Biodiversity folder and the rest in your Motion folder.

e. Questions.

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For Today:

1. In your biodiversity folder, write an account of your sightings, thoughts, questions, reflections on the living things you noticed and observed during WOW (you can include scenes from the train and bus). Include sketches. Mention the various habitats where you saw the organisms. Reflect on how the living and non-living things in the environment interact and depend on one another.
2. In your motion folder, share some of the important experiences with motion. What did you notice while traveling, for example, on the train and bus? What about the zipline? What was your average speed? What was your maximum speed?  (Here is a video of Mr. M. can you use it to figure out speed? <https://www.facebook.com/kylemargenau/videos/10156147710904125/> The first part of the zipline is 400 meter. The return trip is 350 meters.What about the motion of the river? How did you explain the complex currents in the Ganga? What did you do to try to assess the velocity of the small river (Huel) at the Himalayan Bear Stream Camp? Did you notice the apparent motion of the sun during the day? What about the moon? The planets (Mars was quite visible every night)? The stars?
3. The next items are to be recorded in your DSN entry in your motion folder.
4. Review your understanding of motion: distance, time, frame of reference, speed, velocity, constant speed, constant velocity, inertia, changing speed, changing velocity, acceleration, distance vs. time graphs, speed calculations, units.
5. We defined force as a measurable push or pull that causes a change in the velocity of an object. A spring scale is used to measure force. The force being measured is compared to an equal and opposite force being exerted by the spring. A constant force produces a constant acceleration (not a constant speed). At this point, clarify for yourself what the difference is between speed and acceleration, between velocity and acceleration.
6. Look at the data and graphs below. They are selected from the trials completed with the big cart in periods 3 and 4. What do you notice about each case? Be sure to ask questions about anything you do not understand.
7. What is the difference between the results of a single push and of repeated (intermittent) pushes?
8. On a single distance vs. time graph, show the results of the cart’s motion with 8 lbs, 10 lbs, and 12 lbs of force. Reflect on the data from these three cases.
9. Thought experiment–draw what you think the result will be regarding the motion of an object being spun on a string around a central point after the string is released. Make a sketch of the path your expect. Explain why you expect this.
10. New concepts coming up: Momentum, Conservation of momentum, Circular motion, Centripetal acceleration, Gravity as a (rather mysterious) force that operates at a distance–no strings attached, Work, Energy, Conservation of Energy, Forms of Energy.
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Cart moving with one push before the starting line.

Time (seconds)  Distance (meters)

 0 0 0.42 1 1 2 1.48 3 1.91 4 2.67 5 3.24 6

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Cart pulled with 8 pound force (as constant as we could make it).

Time (seconds) Distance (meters)

 0 0 2.43 1 3.39 2 4.34 3 4.68 4 5.55 5 5.93 6

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Cart pulled with 10 pound force (as constant as we could make it)

Time (seconds) Distance (meters)

 0 0 2.21 1 2.97 2 3.74 3 4.43 4 5.05 5 5.54 6

Distance in meters vs. time in seconds for a cart being pulled with a constant force of 10 pounds

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Cart pulled with 12 pound force (as constant as we could make it)

Time (seconds)                                                     Distance (meters)

 0 0 1.75 1 3.14 2 3.64 3 4.26 4 4.77 5 5.01 6

Distance in meters vs. time in seconds for a cart being pulled with a constant force of 12 pounds.

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Cart moving with intermittent impulse delivered in the same direction and of equal magnitude (as best we could do).

Time (seconds)    Distance (meters)

 0 0 1.3 1 2.14 2 3.2 3 3.54 4 4 5 4.08 6

Distance in meters vs. Time in seconds for a cart receiving intermittent impulses of equal magnitude in the same direction as the direction of travel.

Remember