Welcome to Kinematics!

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1 Welcome to Kinematics! Classical Mechanics Mechanics Lecture 1, Slide 1

2 Modus Operandi FlipItPhysics Protocol! Online Prelectures (animated textbook, before lecture)! Online Checkpoints (check knowledge, before lecture)! Lectures (very interac?ve)! Online Homework (first deadline Sunday night, 80% credit for late online homework up to one week late) Mechanics Lecture 1, Slide 2

3 Mechanics Lecture 1, Slide 3

4 Q: What are the benefits of par?cipa?ng? A: You learn more 30 Viewer Non-Viewer Exam Score Students who Exam 1 average Viewed pre-lectures 80% Blew through pre-lectures 73% Mechanics Lecture 1, Slide 7

5 Clicker Question 1 Do you have your i>clicker with you today? A) Yes B) No C) Maybe D) I like pudding Mechanics Lecture 1, Slide 4

6 Clicker Question 2 Which of the following best describes your high-school physics class? A) Great B) Pretty good C) So-so D) Not so good E) Awful Mechanics Lecture 1, Slide 5

7 Classical Mechanics Lecture 1 Today's Concepts: a) Displacement, Velocity, Accelera?on b) 1-D Kinema?cs with constant accelera?on Mechanics Lecture 1, Slide 8

8 graphical representation Your Comments how to idennfy and unlize integrals in formulas and quesnons, just the whole concept. Start by visualizing the graphical representation Can you give me more quesnons to pracnce and not be marked, just pracnce quesnon with right answers and explain. thanks so much. Textbooks are a good source Text the part explaining how distance was related to velocity regardless of Nme went a bit too fast Use the controls to repeat. the most difficult thing is when we look at the v-t graph,then ask what we know about the x-t or a-t graph,especially it is not a constant speed. Perhaps the introducnon of the calculus concept is sexng us up for later in the course? You betcha

9 Formal Problem Solving Formal Problem Solving For the next several assignments while you are working with Unit 4 and the next unit you will be doing a set of kinemancs problems. These help you learn about the elements of formal problem solving. Part 1: Diagrams and Graphs Part 2: Tables and EquaNons Part 3: Algebra and SubsNtuNon Part 4: Checks: ComputaNon and Units This approach was developed by Bob Morse a

10 Formal Problem Solving An example of how to work a typical kinemancs problem is the SAMPLE CONSTANT ACCELERATION PROBLEM. Then there is a packet of 5 problems. Each problem is printed at the top of a sheet enntled CONSTANT ACCELERATION PROBLEM WORKSHEET. You are to do parts of each of the 5 problems during the next few assignments unnl all the parts are completed. This approach was developed by Bob Morse, a teacher at St. Albans School in Washington DC.

11 Displacement and Velocity in One Dimension Displacement Time taken Mechanics Lecture 1, Slide 11

12 Displacement and Velocity in One Dimension The v(t) vs. t plot is just the slope of the x(t) vs. t plot DefiniNon: Speed = v(t) Mechanics Lecture 1, Slide 12

$the le\ correctly related A) YES B) NO Mechanics Lecture 1, Slide$

13 Displacement and Velocity in One Dimension Are the plots shown at the le\ correctly related A) YES B) NO Mechanics Lecture 1, Slide 13

14 Clicker Question The velocity vs.?me plot of some object is shown to the right. Which diagram below could be the Displacement vs.?me plot for the same object? A B C Mechanics Lecture 1, Slide 14

15 Acceleration Mechanics Lecture 1, Slide 15

16 Checkpoint 1 For the Displacement and Velocity curves shown on the le\, which is the correct plot of accelera?on vs.?me? A B Mechanics Lecture 1, Slide 16

Clicker Question 4 Vote again A B A B Typical A answer

time graph. Thus, the answer should be the first graph.

positive value and then decreases to about zero before

Since the velocity graph curves first down then up,

17 Clicker Question 4 Vote again A B A B Typical A answer Because a(t)= dv(t)/dt, according to the graph of velocity vs. time, acceleration vs. time graph should be the slope of the velocity vs. time graph. Thus, the answer should be the first graph. Typical B answer The velocity starts at a high positive value and then decreases to about zero before increasing again. Since the velocity graph curves first down then up, the acceleration decreases and then increases instead of just increasing for the entire time. Mechanics Lecture 1, Slide 17

18 Constant Acceleration constant a(t) = a Mechanics Lecture 1, Slide 18

19 Clicker Question 5? 16ft 9ft 4ft 1ft At t = 0 a ball, ini?ally at rest, starts to roll down a ramp with constant accelera?on. Suppose it moves 1 ft between t = 0 sec and t = 1 sec. How far does it move between t = 1 sec and t = 2 sec? A) 1 \ B) 2 \ C) 3 \ D) 4 \ E) 6 \ Mechanics Lecture 1, Slide 20

20 Checkpoint 2 Responses 3 16ft 9ft 4ft 1ft A B D E Typical A answer If it moves 1h in 1 sec, using x=x o +vt, v=1/1 or 1m/s. Using v=v o +at, a=1/1 or 1h/s 2. So in the interval of 1 second, the ball will move 1 foot. Typical B answer For the first second, the velocity is 1 h/s. Therefore if acceleranon is constant, then velocity will have increased to 2 h/s at 2 seconds. Therefore, in the Nme interval between 2 and 1 seconds, the ball would have moved 2 feet. Typical C answer AcceleraNon is 1 h/s 2 and the velocity at the end of the first interval is 2h/s so at the second interval the distance is 3 h from the equanon d= v + 1/2 at 2 Mechanics Lecture 1, Slide 21

Checkpoint 2 Responses 3 16ft 9ft 4ft 1ft Typical D answer Since acceleranon is constant, we can solve for acceleranon using the formula x = v(ininal) * t + 0.5at 2.

21 Checkpoint 2 Responses 3 16ft 9ft 4ft 1ft Typical D answer Since acceleranon is constant, we can solve for acceleranon using the formula x = v(ininal) * t + 0.5at 2. Doing this we solve acceleranon for m/s 2, aher gexng this we can plug this in for total distance travelled and the answer comes out to 4h if calculated properly. A B C D E Question asks for distance from t=1 s to t=2. Typical E answer The equanon v f = v o + at will give us the final velocity and with that the final displacement. Given that v o = 1 foot/second, a = 4.9 (this is true due to the gravitanonal pull from the ramp assuming a 30 ramp) and t to be 1s. This calculates to the final an swer being approximately 5.9 m. g 9.8 ft/s 2 angle not necessarily 30 Mechanics Lecture 1, Slide 21

23 Measure posinon with ruler. EsNmate tenths of mm Convert to actual posinon in metres Note that t 0 is t=0 s but not x = 0 m.

24 acceleranons, <a i >, at the same Nmes Where to plot <v> and <a>?

Welcome to Kinematics!

Welcome to Kinematics! Classical Mechanics Mechanics Lecture 1, Slide 1 Modus Operandi SmartPhysics Protocol Online Prelectures (animated textbook, before lecture) Online Checkpoints (check knowledge,