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Newtonia An Introduction to Net Force and Changes in Motion

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1 Newtonia An Introduction to Net Force and Changes in Motion
tinyurl.com/newtonia

2 Newtonia: What TEKS?: 6.8B identify and describe the changes in position, direction, and speed of an object when acted upon by unbalanced forces 6.8D  measure and graph changes in motion; 6.8D Students will investigate the relationship between force and motion using a variety of means, including calculations and measurements 8.6A Demonstrate and calculate how balanced forces change the speed or direction of an object's motion 8.6B Differentiate between speed, velocity, and acceleration 8.6C Investigate and describe applications of Newton's law of inertia, law of force and acceleration, and the law of action-reaction such as vehicle restraints, sports activities, amusement park rides, Earth's tectonic activities, and rocket launches.

3 Table of Contents What is it?: An introductory lesson sequence for Newton’s Laws Using a Computer Simulation (Url: tinyurl.com/Newtonia) What is needed?: Best if each student or pair of students have a computer with ability to connect to internet & copies of handouts (or respond in notebook). Can be done with just a teacher machine running simulation. Doc camera can be useful for sharing student results and discussing patterns. Pages 3&4 and pages 6&7 can be printed front-and-back to hand out to students. Additional copies of 6&7 can be used for still more challenges. Browser: Use Firefox or Explorer (not Chrome) Introductory Questions (To be completed before activity) for handout, print 4 to a page or use pdf pages Activity – Introductory notes/observation followed by a shared challenge and possible additional challenges. Revisit Selected Introductory Questions plus Additional Questions (could be homework or used in class). Additional Resource – Acceleration Assessment Items (& Key) – Released TAKS Item and Non-Dichotomous Multiple Choice Item

4 (b) Which color (red or blue) goes with which directions? N/S vs. E/W?
[1] Velocity (How Fast) Graphs – Press Go and experiment with the N S E and W buttons to see what they do. Press Go again to pause the simulation. What do the lines on this graph represent? A higher line (above or below zero) means what? Where is zero for both lines? (b) Which color (red or blue) goes with which directions? N/S vs. E/W? (c) If you don’t press a button (don’t apply a Net Force) describe the motion: Name: Period: START PAUSE Note: You must press the Go button to start the simulation. To pause, press the Go button again.

5 2 Objective - PART A: __Get the Donut to Move Diagonally Up and to the Right_______ Sketch the velocity graphs for Part A (use dashes for blue line). The end of the sketch is the most important. N (+) S (-) E (+) W(-) Tally Marks Totals +/- VERTICAL (i) combine HORIZONTAL combine Objective - PART B: ___Now get the Donut to Move Horizontally to the Right ______ Sketch the velocity graphs for Part B (use dashes for blue line). The end of the sketch is the most important. N (+) S (-) E (+) W (-) Additional Tally Marks Additional Totals +/- VERTICAL (ii) combine HORIZONTAL combine Could you end up with these same totals but with different values for (i) & (ii)? Explain: N (+) S (-) E (+) W (-) Overall Totals for Each Direction: The # from (i) + the # from (ii) +/- VERTICAL combine HORIZONTAL Name: Period: Partner(s): combine

6 Discussion and Other Possible Newtonia Objectives
Group 1 Results Group 2 Results [1] Use document camera or copy selected tables on white board to share results from different groups. [2] In addition to individual solutions, what patterns emerge in terms of part (a) getting the donut to move diagonally, (b) then horizontally and then the totals from (I + ii ) after it is moving horizontally? [3] A way of clarifying the patterns is to ask how could we tell if a result would NOT work? Hinting at the possibility of additional forces, if an object is moving horizontally but later is observed to be moving downward (gravity) or slowing (friction) what additional forces are present? Discuss in terms of NET force ≠ 0 causing an acceleration (≠ 0) or a change in motion. What patterns do we notice in (a), (b) and then in the totals? What other Two-Part Objectives might we try? Examples of Additional Two-Part Objectives (use to fill in blanks) Objective 2: (a) Move and then stop (b) Move again and then stop Objective 3: Start off moving at a constant velocity in one direction and then: (a) Change the direction and speed of the object (b) Return to the original velocity (original direction and speed) Objective 4: Turn on Friction by dragging (or clicking) slider to 1. Then: Get the object to move at a relatively constant velocity Now get the object to stop How are the patterns from others likely to be the SAME and also DIFFERENT from what you got? (relatively constant)

7 Objective - PART A: _____________________________________________________
Sketch the velocity graphs for Part A (use dashes for blue line). The end of the sketch is the most important. N (+) S (-) E (+) W(-) Tally Marks Totals +/- VERTICAL (i) HORIZONTAL Objective - PART B: _____________________________________________________ Sketch the velocity graphs for Part B (use dashes for blue line). The end of the sketch is the most important. N (+) S (-) E (+) W (-) Additional Tally Marks Additional Totals +/- VERTICAL (ii) HORIZONTAL Could you end up with these same totals but with different values for (i) & (ii)? Explain: N (+) S (-) E (+) W (-) Overall Totals for Each Direction: The # from (i) + the # from (ii) +/- VERTICAL HORIZONTAL Name: Period: Partner(s):

8 Objective - PART A: _____________________________________________________
Sketch the velocity graphs for Part A (use dashes for blue line). The end of the sketch is the most important. N (+) S (-) E (+) W(-) Tally Marks Totals +/- VERTICAL (i) HORIZONTAL Objective - PART B: _____________________________________________________ Sketch the velocity graphs for Part B (use dashes for blue line). The end of the sketch is the most important. N (+) S (-) E (+) W (-) Additional Tally Marks Additional Totals +/- VERTICAL (ii) HORIZONTAL Could you end up with these same totals but with different values for (i) & (ii)? Explain: N (+) S (-) E (+) W (-) Overall Totals for Each Direction: The # from (i) + the # from (ii) +/- VERTICAL HORIZONTAL Name: Period: Partner(s):

9 Summary Name: ___________________________ Period: ________
[1] For Newton, a NET FORCE (imbalanced force or Net Force ≠ 0) causes a CHANGE IN MOTION (change in velocity) or ACCELERATION. (a) How can you tell from just looking at the velocity graph which button you pressed? (be sure to mention color and direction +/-) N: S: W: E: (b) Using the SUMMARY, consider your answers to these questions. For each scenario write if there is a non-zero NET force (Hint: Is there a change in motion?): (ii) Which results in a change in motion (velocity) (ii) An acceleration (≠ 0) Name: ___________________________ Period: ________ (i) A Net Force (≠ 0) N causes Summary Net Force (≠ 0) ? (Y/)N) How do you know? Net Force (≠ 0) ? (Y/)N) How do you know? Net Force (≠ 0) ? (Y/)N) How do you know?

10 [5] Circle response for each section of graph
Velocity increasing :: decreasing :: constant Acceleration positive :: negative :: zero Net Force positive :: negative :: zero (b) Velocity increasing :: decreasing :: constant (c) Velocity increasing :: decreasing :: constant (d) Velocity increasing :: decreasing :: constant (e) Velocity increasing :: decreasing :: constant c d e b a [6] (a) Create a story about an object and state explicitly where the object experiences a net positive (+), a net negative (-) and a net zero (0) force. Be sure to say how the object starts off moving. (b) Draw a graph for this story and label the corresponding parts with +/-/0. Be sure to say how the object starts off moving.

11 Introductory Questions

12 Newtonia - Intro Questions
© generative design center at utaustin

13 Name _________________________
[1] [i] The rocket wants to move in the direction shown. Which direction should the rocket be fired? [a] [b] rocket in space & far from any other object [ii] In terms of causing movement this process is most like [a] throwing a watermelon off the back of a canoe [b] an oil refinery burning off excess natural gas [c] bouncing on a trampoline [d] blowing pieces of paper off a desk [iii] Briefly explain your answer to [ii]

14 [2] A rocket is moving in the direction shown. Later it is observed moving horizontally. In which direction(s) must the rocket have been pushed. [a] [b] [c] both & [d] none of these

15 [b] zero TOTAL (net) pushes [c] [d] b&c [e] none of these
[3] A rocket is stopped. Later it is stopped in another location. Which of the following pushes could have happened? [a] no pushes [b] zero TOTAL (net) pushes [c] [d] b&c [e] none of these

16 [4] A rocket is moving at a constant speed in the direction shown. Later it is moving the same direction & speed. Which of the following pushes could have happened? [a] no pushes [b] zero TOTAL (net) pushes [c] [d] a, b &c [e] none of these

17 [a] about one time every three seconds
[5] The rockets on Rocket Randi’s sled fire for one second at a time. To move at an average speed of 20 cm/sec Randi fires the rockets about one time every three seconds. Randi then gets the sled to move at 40 cm/sec on the same surface. To stay at this new speed, Randi would have to fire the rockets: [a] about one time every three seconds [b] close to two times every three seconds [c] more than two times every three seconds [d] between one and two times every three seconds [e] none of these

18 [a] The net force on the sled is zero.
[6] Rocket Randi’s sled is observed to be moving to the right. Circle all responses that could be true at the moment the observation is made: [a] The net force on the sled is zero. [b] The net force on the sled is to the right. [c] The net force on the sled is to the left. [d] The momentum (inertia) is to the right

19 Key for Introductory Questions
[1] (a) Watermelon off canoe – We push on melon, melon pushes back [what is mean by “equal and opposite” phrase] causing canoe to move (Gas fired from rocket is like watermelon being thrown; Like releasing an inflated balloon). May want to discussion [1] prior to activity. Others can be discussed at greater length during/after activity. [2] (a) need to cancel upward part so only (a) “MUST” be the case. Yes, (c) would work but the horizontal push is NOT required. [3] (d) b and c if located in a new position. [4] (d) a, b & c [5] (a) Force needed is same for any constant velocity (not including air resistance … the speeds given are relatively slow so air resistance should be very small). [6] All four responses are correct. On tests “inertia” has a meaning similar to what we call “motion”.

20 Extension ACCELERATION

21 [1] Acceleration (change in How Fast) Graphs – Press Start Over, move the donut to the middle of the screen (click and drag to move). Wait for count-down (or click white square). [2] Press Go to start the simulation. Then press N/S/E/W buttons a number of times. Press Go again Pause. [3] Move Force slider to 1.5 and repeat [2]. [4] Move slider to 0.5 and repeat [2]. [5] Return slider to 1.0 (ii) Which results in a change in motion For Newton, a NET FORCE (imbalanced force) causes a CHANGE IN MOTION (change in velocity) or ACCELERATION. In the simulation every time you press the N/S/E/W buttons you apply a NET FORCE. When you do this, what happens to the acceleration graph? (b) How can you tell from just looking at the acceleration graph which button you pressed? (be sure to mention color and direction +/-) N: S: W: E: (ii) An accleration (i) A Net Force causes

22 (i) A Net Force (≠ 0) N causes
[6] For Newton, a NET FORCE (imbalanced force or Net Force ≠ 0) causes a CHANGE IN MOTION (change in velocity) or ACCELERATION. (a) How can you tell from just looking at the acceleration graph which button you pressed? (be sure to mention color and direction +/-) N: S: W: E: (b) Using this SUMMARY, consider your answers to these questions. For each scenario write if there is a non-zero NET force (Hint: Is there a change in motion?): (ii) Which results in a change in motion (ii) An acceleration (i) A Net Force (≠ 0) N causes Net Force (≠ 0) ? (Y/)N) How do you know? Net Force (≠ 0) ? (Y/)N) How do you know? Net Force (≠ 0) ? (Y/)N) How do you know?

23 Assessment TWO RELATED ITEMS

24 1. 2. Name: _______________________ Class Period: __________
This question may have more than one correct answer. Select all correct responses. A child jumps on a trampoline, as shown above. Which of the following causes the child to rise in the air. A Inertia B Mass C A reaction force D A gravitational force An elevator is moving upward. Which of the following statements could be true: A There is a net Force downward on the elevator. B There is a net Force upward on the elevator. C The net Force on the elevator is 0 Newtons. D The elevator has no weight.

25 ANSWER KEY 1. 2. Set gravity to 1 Illustrate with Newtonia – All 3 scenarios could be true TAKS Item This question may have more than one correct answer. Select all correct responses. A child jumps on a trampoline, as shown above. Which of the following causes the child to rise in the air. A Inertia B Mass C A reaction force D A gravitational force An elevator is moving upward. Which of the following statements could be true: A There is a net Force downward on the elevator. B There is a net Force upward on the elevator. C The net Force on the elevator is 0 Newtons. D The elevator has no weight Motion a better word for “Inertia” Moving upward but Net Force down (gravity winning) Applied force equal to OR greater than gravity (Net Force ≥ 0). Unfortunately this is an “action – reaction” question (see watermelon response in intro) Applied force equal to gravity (Net Force = 0). With gravitation, if an object has mass it DOES have weight


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