Test Wed, Feb 8 th 7pm, G20 MING HSIEH Bring your calculator and #2 pencil with a good eraser! 20 Multiple choice questions from:

Transcription

1 Test Wed, Feb 8 th 7pm, G0 MING HSIEH Bring your calculator and # pencil with a good eraser! 0 Multiple choice questions from: Chapter 1 (except section 1. and 1.7): Unit conversions, estimating, trigonometry, scientific notation Chapter (all of it) Displacement, velocity, acceleration, free fall Chapter 3 (except section 3.5) Adding vectors, finding components of vectors, projectile motion

2 Estimates Make estimates based on your knowledge, convert numbers to order of magnitude (powers of 10) Estimate the number of breaths taken by a human being during an average lifetime. ~1 breath per second 3600 seconds per hour ~10 3 s/h 4 hours per day ~10 h/d 365 days per year ~10 d/y years ~ 10 y/lifetime (1 breath)(10 3 s/h)(10 h/d)(10 d/y)(10 y/lifetime) = 10 8 breaths

3 Conversions and Sig Figs A rectangular building lot measures 104 ft by 151 ft. Determine the area of this lot in square meters (m ).

4 Displacement, Velocity, Acceleration x x f x i v x t x t f f x t i i a v t f f v t i i v t

5 Motion at constant acceleration v v o at x v t o 1 at v vo ax

6 Use the Pro Tips! Pro Tip #1: Draw a picture Pro Tip #: Label Frame of Reference Pro Tip #3: List what you know in variable form

7 Position Time Graphs Summarized downward (\)

8 Velocity Time Graphs Summarized the slope of a velocity-time graph is the acceleration horizontal graph segments indicate that the object has constant velocity graph segments above the x-axis imply movement in the positive direction graph segments below the x-axis imply movement in the negative direction horizontal segments on the x-axis indicate no movement straight line graph segments indicate constant acceleration (--, / or \) a change of direction is indicated whenever the graph crosses the x-axis an increase in speed (magnitude of velocity) is indicated by graph segments moving away from the x-axis

9 Acceleration Time Graphs Summarized horizontal graph segments indicate that the object has constant acceleration a horizontal graph segment on the x-axis indicates that the object has constant velocity (no acceleration) graph segments above the x-axis imply positive acceleration graph segments below the x-axis imply negative acceleration no changes in direction may be inferred from these graphs

10 Free Fall Objects falling near Earth due to gravity Constant acceleration with g=9.8 m/s +y Define +y down: use a=+g Define +y up: use a= -g +y

11 Vector Arithmetic Components Components of a vector (commonly velocity) Recall for right triangles: These are formulas with three variables. If you know, you can solve for the other. sin cos tan opposite hypotenuse adjacent hypotenuse opposite adjacent adjacent (adj) a b opposite (opp) c Pythagorean Theorem

12 Adding vectors A force F 1 of magnitude 6.30 units acts on an object at the origin in a direction θ = 40.0 above the positive x-axis. (See the figure below.) A second force F of magnitude 5.00 units acts on the object in the direction of the positive y-axis. Find the magnitude and direction of the resultant force F 1 + F.

13 Motion in Two Dimensions With Constant Acceleration Separation of vectors into components allows separation of equations into components: v v a t x xo x x v t a t xo 1 x xo x v v a x x v v a t y yo y y v t a t yo 1 y yo y v v a y y

14 v x x x v o xo Projectile motion v xo t v y y v y o yo gt v yo t 1 gt v o o intial velocity vector initial direction of velocity vector or t v y = 0 at top of trajectory v x = v xo remains the same throughout trajectory because there is no acceleration along the x-direction

15 Two balls, one twice as massive as the other, roll off a horizontal table with the same v x0 when they leave the table. In this situation: a) The heavier ball hits the ground in half the time as the lighter one. b) The heavier ball hits the ground in twice the time as the lighter one. c) The heavier ball hits the ground in much less time than the lighter one, but not necessarily half the time. d) The heavier ball hits the ground in much more time than the lighter one, but not necessarily half the time. e) The balls hit the ground at the same time.

16 Two balls, one twice as massive as the other, roll off a horizontal table with the same v x0 when they leave the table. In this situation: a) The heavier ball hits the ground in half the time as the lighter one. b) The heavier ball hits the ground in twice the time as the lighter one. c) The heavier ball hits the ground in much less time than the lighter one, but not necessarily half the time. d) The heavier ball hits the ground in much more time than the lighter one, but not necessarily half the time. e) The balls hit the ground at the same time.

17

18

19

20

21