Unit I Review Worksheet Key

Transcription

1 Unit I Review Workheet Key 1. Which of the following tatement about vector and calar are TRUE? Anwer: CD a. Fale - Thi would never be the cae. Vector imply are direction-conciou, path-independent quantitie which depend olely upon the initial and final tate of an object. Vector are alway expreed fully by ue of a magnitude and a direction. b. Fale - Both calar and vector quantitie have a magnitude or ize expreed with a given unit; additionally, a vector quantity require a direction in order to fully expre the quantity. c. True - Vector are fully decribed by magnitude AND direction; calar are not decribed with a direction. d. True - Scalar uch a ditance would depend upon the path taken from initial to final location. If you run around the track one complete time, your ditance will be different than if you take a tep forward and a tep backward. The path MATTERS; ditance (like all calar) depend upon it. On the other hand, the diplacement (a vector quantity) i the ame for both path. e. Fale - Vector are the type of quantitie which depend only upon initial and final tate of the object. For intance, the vector quantity diplacement depend only upon the tarting and final location. f. Fale - Thi i certainly not a peed quantity; though the unit i appropriate for peed, the tatement of the direction i inconitent with peed a a calar quantity. 2. Which of the following tatement about ditance and/or diplacement are TRUE? Anwer: BDF a. Fale - Ditance i the calar and diplacement i the vector. Know thi one! b. True - Diplacement i the change in poition of an object. An object which finihe where it tarted i not diplaced; it i at the ame place a it tarted and a uch ha a zero diplacement. On the other hand, the ditance i the amount of ground which i covered. If it wa truly a journey, then there i definitely a ditance. c. Fale - Thi would only be the cae if the peron walked along a beeline path from A to B. But if the peron make a turn and veer left, then right and then..., then the peron ha a ditance which i greater than the length of the path from A to B. Ditance refer to the amount of ground which i covered. d. True - If a peron never change direction and maintain the ame heading away from the initial poition, then every tep contribute to a change in poition in the ame original direction. A 1 m tep will increae the diplacement (read a out of place-ne) by 1 meter and contribute one more meter to the total ditance which i walked.

2 Unit I Review Workheet Key Page 2 e. Fale - Ditance i a calar and i ignorant of direction. The "Northwet" on thi quantity would lead one to believe that thi i a diplacement (a vector quantity) rather than a ditance. f. True - The unit i an appropriate diplacement unit (length unit) and the direction i tated. Since there i both magnitude and direction expreed, one would believe that thi i likely a diplacement. g. Fale - The ditance from A to B i 35 yd; from B to C i 2 yd; and from C to D i 35 yd. The total ditance moved i 9 yd. h. Fale (a rather picky FALSE) - Technically, thi i not a diplacement ince diplacement i a vector and fully decribed by both magnitude and direction. The real expreion of diplacement i 5 yd, left (or Wet or -) 3. Olympic gold medalit Michael Johnon run one time around the track - 4 meter - in 38 econd. What i hi diplacement? _ meter _ What i hi average velocity? m/ Michael finihe where he tarted, o he i not "out of place." Hi diplacement i meter. Since average velocity i diplacement over time, hi average velocity i alo m/. 4. Which one of the following quantitie i NOT a vector? a. 1 mi/hr, Eat b. 1 mi/ec, Wet c. 35 m/, North d. 2 m/ A vector ha both magnitude and direction. Only choice d doe not how a direction; it mut be a calar. 5. The average peed of an object which move 1 kilometer (km) in 3 minute i _. a. 1 km/hr b. 2 km/hr c. 3 km/hr d. more than 3 km/hr The average peed i ditance/time. In thi cae the ditance i 1 km and the time i.5 hr (3 minute). Thu average peed = (1 km)/(.5 hr) = 2 km/hr 6. Which one of the following quantitie i NOT a peed? a. 1 mi/hr b. 1 mi c. 35 m/ d. 2 m/ You can often tell a quantity by it unit. 1 mi i a ditance. The quantity peed ha unit of ditance/time.

3 Unit I Review Workheet Key Page 3 7. Which of the following tatement about velocity and/or peed are TRUE? Anwer: ADEGI a. True - Ye! Speed i a calar and velocity i the vector. Know thi one! b. Fale - Speed refer to how fat an object i moving; but velocity refer to the rate at which one' motion put an object away from it original poition. A peron can move very fat (and thu have a large peed); but if every other tep lead in oppoite direction, then that peron would not have a large velocity. c. Fale - Peron Y ha one-half the peed of Peron X. If peron Y require twice the time to do the ame ditance, then peron Y i moving half a fat. d. True - Ye! That i exactly the definition of velocity - the rate at which velocity change. e. True - An Indy Race car driver i a good example of thi. Such a driver i obviouly moving very fat but by the end of the race the average velocity i eentially m/. f. Fale - The preence of the direction "Wet" in thi expreion rule it out a a peed expreion. Speed i a calar quantity and direction i not a part of it. g. True - For a round trip journey, there i no ultimate change in poition. A uch, the average velocity i m/t econd. Regardle of the time, the average velocity will be m/. h. Fale - The direction of the velocity vector depend only upon the direction that the object i moving. A wetward moving object ha a wetward velocity. i. True - A dicued in #2g, the ditance traveled i 9 meter. When divided by time (8 minute), the average peed i yd/min. j. Fale - The average velocity would be yd/min only if the peron return to the initial tarting poition. In thi cae, the average velocity i 5 yd/8 min, wet (6.25 yd/min, Wet). 8. Which of the following tatement about poition-time graph are TRUE? Anwer: ACD a. True - A traight diagonal line i a line of contant lope. And if the lope i contant, then o i the velocity. b. Fale - Not necearily true. If the object i at ret, then the line on a p-t graph will indeed be horizontal. However, it will not necearily be located upon the time axi. c. True - Since lope on a poition v. time graph repreent the velocity, a poitive lope will repreent a poitive velocity. d. True - Since lope on a poition v. time graph repreent the velocity, a negative lope will repreent a negative velocity.

4 Unit I Review Workheet Key Page 4 9. Determine the magnitude of the diplacement (in meter) of an object which a. move from Hither to Yon (with an average peed of 28. m/) and then back to Hither (with an average peed of 28. m/) if both the forward and the return trip take 46 minute each. The diplacement of an object i it change in poition. Since in thi cae the object tart in Hither and end in Hither, the total diplacement of the object i m. b. move at a contant peed of 8.3 m/ in a traight line for 15. econd. Since the velocity (peed and direction) i contant, the diplacement i equal to the velocity time the time. x vt x 8.3m 15. x 125 m 3 ig fig 1. Conider the poition v. time graph at right. a. Determine the average velocity of the object. Average velocity i the diplacement divided by the time. x v t 5. m v 6. v 8.3m 2 ig fig b. Write a mathematical model to decribe the motion of the object. Be ure to ue appropriate variable and unit! x (m) t () x 8.3m t 1. m

5 Unit I Review Workheet Key Page 5 v m 11. Shown at right i a velocity v. time graph for an object. 4 a. Decribe the motion of the object. The object move to the right at 4 m/ for 2, 2 the move back to the left at 3 m/ for 1, and then top for 2. t () b. Draw the correponding poition v. time graph. Aume x m. -2 x (m) t () -4 c. Uing the graph above, how far did the object travel in the interval t 1 tot 2? Diplacement i the area under the curve of a graph of velocity v. time a hown on the graph above. x 4m x 4 m 1 d. What i the total diplacement? Explain or how how you got the anwer. Total diplacement would be the total area under the curve of the velocity v. time graph above. 4 m 2 3m 1 x x 5 m The total diplacement could alo be found uing the poition time graph above. x x xo x 5 m m x 5 m e. Draw a motion map for the object. x

6 Unit I Review Workheet Key Page Johnny drive from Arizona to Wiconin (192 mile) in 32 hour. He return to Arizona by the ame route in 4. hour. a. Determine hi average peed. b. Determine hi average velocity. total ditance v diplacement x total time v total time t mile v 2 32 hour 4. hour v 2 32 hour 4. hour v 53m m v 13. Conider the v v. t graph below. v m t () c. Draw a motion map that model the behavior of the object. a. Decribe the behavior of the object depicted in the graph. The object move to the right at 3. m/ for 4. then top for 2. then move to the left at 2. m/ for 4.. b. Draw the correponding poition v. time graph. Aume it tart at the origin. x (m) x t () 14. A racecar travel at a peed of 95 m. How far doe it travel in 12.5? Ue the appropriate mathematical model and how how unit cancel. (Keep the proper number of ignificant figure.) d vt d 95m m 2 ig. d fig.