IB Physics, Bell Work, Jan 16 19, 2017

Transcription

1 IB Physics, Bell Work, Jan 16 19, 2017 IB Physics: Scientific thinking, 5% rule, linearization, relationships, proportionality, interpreting graphs, period, amplitude, pendulum, conversions

2 IB Physics Bell Work, Monday, Jan What does negligible mean? A negligible means insignificant (doesn t matter). A negligible quantity can be ignored and set to a value of zero. 2. Is the y-intercept of this graph insignificant (negligible) or significant? Why or why not? Sketch the graph & copy the data Thing on y axis x y y = x Thing on x axis (5, 75)

3 Something on y axis IB Physics Bell Work, Monday, Jan Is the y-intercept insignificant? Why or why not? If b < = 5% of y max then b is insignificant and b can be = 0 If b > 5% of y max then b is significant and b can not be = 0 Y max = largest value of y in a data set. x y max = 75 5% of 75 = 3.75 b = - 5, b = 5 b > y max because 5 > 3.75 y y = x something on x axis (5, 75) Thus the y-intercept is significant (not negligible) and can not be set to 0.

4 IB Physics Bell Work, Tuesday, Jan Sketch each graph. Describe the relationship between the variables x & y for each graph. Write an equation that will express each graph in linear form. Sketch the graphs. a a. Y is directly proportional to x, linear y α x, x bigger, y bigger by same amount. y= mx + b b. Y is inversely proportional to x. b y α 1 x reciprocal of x. x bigger, y smaller by the y = m 1 x + b

5 Physics Bell Work, Tuesday, Jan 17 c c. Y is proportional to the square of x. y α x 2 y= mx 2 + b e d d. The square of y is proportional to x. y 2 α x y 2 = mx + b e. As x increases, y remains the same. There is no relationship between the variables. y = b Or y is constant

6 IB Physics Bell Work, Tuesday, Jan 17 f. Y is not proportional to x, because the line does not go through the origin. Y is linearly and negatively related to x. As x increases, y decreases. y= - mx + b Y is not proportional to x, because the line does not go through the origin. Y is linearly and positively related to x. As x increases, y increases. y= mx + b

7 Something on y axis IB Physics Bell Work, Wednesday, Jan Is the y-intercept insignificant? Why or why not? Can b = 0? y max = 75 Use the absolute value of b b = -3 = y = x Another thing on x axis (5, 75) if b y max x100 5 then b is insignificant (b can be set = 0) if b then b is significant (b cannot y max x100 > 5 equal to zero) b ymax x 100 = 3/ = 4 so b /y max < 5 b is insignificant, thus b is negligible so b can be set to 0

8 Snoberknockers IB Physics Bell Work, Wednesday, Jan y = -2x Rigmaroles 2. Is the y-intercept of this line significant? Why? Yes the y intercept is significant. Y-intercepts of lines with negative slopes are almost always significant.

9 Physics Bell Work, Wednesday, Jan 18, How many m are equivalent to 3 cm? 3 cm? m Relationship: How many m = how many cm? cm 100 = m 1 3 cm Should our answer be a number bigger or smaller than 3? Should we multiply 3 by 100? Or divide 3 by 100? _3_cm = m? To get a smaller number for an answer, divide or multiply by whole number? 100 m = 0.03 m Given Relationship # Answer Small unit big unit = smaller answer Big unit small unit = bigger answer X

10 Cost ($) Physics Bell Work, Thursday, Jan What does the slope of this graph tell you? 2. What are the units for the slope of this graph? 3. What could the y-intercept mean in this situation? 4. Write a model equation for this graph Sketch the graph. Slope = 20 y-intercept = 7.50 Online Shoe Store Shoes (pairs)

11 Physics Bell Work, Thursday, Jan What does the slope of this graph tell you? The average cost of one pair of shoes in dollars. 2. What are the units for the slope of this graph? dollars pairs 3. What could the y-intercept could mean in this situation? The shipping cost for the order. 4. Write a model equation for this graph. Cost = 20 dollars pairs shoes dollars

12 IB Physics Bell Work, Thursday, Jan For a swinging pendulum, what is amplitude (A)? It is a measure as an angle or a distance from the rest point of the swing bob. 3. What is the period (T) of a pendulum? The period of a pendulum (T) is the amount of time in seconds it takes the pendulum to make a complete swing forward and back to The starting point. If you are out of room on your Bell Work sheet, write this on your study guide.