Name: Dae: AP Physics Per. Uni Homework. A car is driven km wes in hour and hen 7 km eas in hour. Eas is he posiive direcion. a) Wha is he average velociy and average speed of he car in km/hr? x km 3.3km/ hr 3hr b) If he car drives km wes a km/hr and hen drives 7 km eas a 3. km/h, wha is he average velociy of he car for he enire rip? x km? We need he ime aken for each par of he rip: Par Par 7 km/ hr 3.km/ hr. Examine he posiion-ime graph a righ.hr x km km 3.3km/ hr ( ) 3hr x (m) d 5km s av 5km/ hr 3hr A B C.hr D E F 5 5 5 3 35 Time (s) a. How far does he objec ravel beween and 3 s? oal ground covered in 3s is 7m b. How far does i ravel beween 3 s and 35 s? oal ground covered in 3-35s is 5m c. Wha is he displacemen of he objec beween 3 s and 35 s? x 3o35s = x 35s -x 3s = 3-5 = -m d. A which poins is he velociy posiive? Velociy is he slope of he x- graph. V is posiive a A, B, F, when he slope of he x- is posiive
e. A which poins is he velociy negaive? Velociy is he slope of he x- graph. V is negaive a E, when he slope of he x- is negaive f. A which poins is he velociy abou zero? Velociy is he slope of he x- graph. V is abou zero a C, D, when he slope of he x- is abou zero g. Wha is he average velociy of he objec for he firs 3 s h. Wha is he average speed of he objec for he firs 3 s i. A which poins is he acceleraion posiive? Acceleraion is in he direcion of v. To deermine if v is + or a each poin, look a v (he slope) righ before and righ afer he poin and evaluae wheher he change in he slope is + or -. Check wih cheerio bowl. a is posiive a B, D, and F j. A which poins is he acceleraion negaive? A and C k. A which poins is he acceleraion abou zero? E (inflecion poin) x 5 m m/ s 3s s d 7m av 3 s 3. walker and a runner leave your fron door a he same ime. They move in he same direcion a consan velociies. Describe he posiion-ime graphs of each. A ime, boh graphs sar a posiion (home). Boh x- graphs are linear wih posiive slopes, bu he runners has a seeper slope (larger velociy)
v (m/s) x (m). The following graphs represen he moions of wo bicycliss. Wih which of he saemens abou he moions do you agree? Explain your choice. 5. Bike A Bike B a) Bike A sared moving a consan posiive velociy. Disagree, velociy is increasing a b) Bike B climbed over a fla hill. No enough info. Graph only shows -d moion c) Bike A sopped wice during he rip. Disagree, oher han a he sar, v = only once d) Bike B sopped wice during he rip. AGREE, in he horizonal pars, posiion is no changing e) The las par of he rip bike A was no moving. Disagree, he velociy is consan and negaive, i is NOT zero f) The las par of he rip bike B was moving a consan speed in he negaive direcion. Disagree, for he very las par, he posiion is no changing, i remains a one negaive posiion g) The las par of he rip bike A was moving a consan speed in he negaive direcion. AGREE h) When we sared observing Bike B i was moving a consan posiive velociy. AGREE, slope (velociy) is posiive and consan. i) When we sared observing bike A i was moving a increasing velociy in he posiive direcion, hen i reached some consan velociy (posiive) and coninued moving for a while, hen is velociy sared decreasing and i some poin i became zero. The i coninued o increased in he negaive direcion unil i reached some new velociy which i mainained for a while. AGREE j) When we sared observing bike B i was moving a consan velociy in he posiive direcion, hen i sopped for a while, hen i sared going back o he origin and hen in he negaive direcion. Finally i sopped AGREE
Posiion (m) Velociy (m/s) 5. - - - - Blue Car: Posiion vs. Time Time (s) Red Car: Velociy vs. Time - - - - Time (s) The wo graphs above may look similar, bu hey acually represen wo very differen moion paerns. Calculae he answers o he following for boh he Red car and he Blue car: velociy a = 3 seconds average velociy from = s o = s velociy a = 5 seconds average velociy from = s o = s maximum speed for he whole rip In which inerval(s) was he car s velociy negaive displacemen during he firs seconds displacemen during he firs seconds During which ime inerval(s) was he car s velociy zero During which inervals was he car s acceleraion zero A wha ime(s) did he car change direcion? BLUE CAR m/s (slope of x- a 3s) m/s (slope of x- beween -s) m/s (same as slope of -s region) -3 m/s (slope of x- beween -s) 3 m/s (max magniude of slope of x-) -s (where x and slope are negaive) m (x-x) m (x-x) -s (where slope of x- is zero) All inervals (all inervals are sraigh lines, consan velociy) A s, -s RED CAR m/s (face value) m/s (average of v and v OR x/) m/s (face value) m/s (average of v and v OR x/ ) m/s (max absolue value of v) -s (where v is negaive) m (area beween -s) m (area beween -s) A s and a s (face value) -s, -s (where slope of v- is zero) s (where v goes from + o -)
v (m/s). Refer o he following v- graph of an objec s moion. Plo he corresponding posiion-ime and acceleraion-ime graphs. - - - - - - - - - Shade or check he ime inervals ha apply for he v- graph given above -3s 3-5s 5-s -s -9s 9-3s 3-5 none Moving in + direcion Moving in - direcion A res Speeding Up A sec Slowing Down Consan speed Greaes disance Leas disance Negaive acceleraion Posiive acceleraion Greaes acceleraion (magniude) When does he objec change direcion? A sec Wha is he acceleraion a s?.7m/s (same as he slope of he enire -3s region) a s? m/s (same as he slope of he enire 3-5s region) a 7 s? -m/s a s? m/s Wha is he average velociy for he firs 3 sec? x/ = m/3s = 7.m/s OR since acceleraion is consan for firs 3s, is jus he average value of ini and final velociy (+)/
a (m /s) v (m/s) x=9 x (m) Using he same v- graph, plo he corresponding posiion-ime and acceleraion-ime graphs (place he horizonal axis appropriaely, scale appropriaely). Check your answers above (in he able and quesions) wih he x- and a- graphs 9 5 5 - - - - - - - - - - - - - x= x= x= - x= - x= - - - - - -
Wha is he average velociy for he firs sec? x/ = m/s = 7.75m/s Can ge x from he area under he v- graph or direcly from he x- graph Wha is he average velociy beween and s? x/ = 3m/s =.5m/s Can ge x from he area under he v- graph or direcly from he x- graph Wha is he average speed for he firs sec?? d/ = / = 7.75m/s Can ge d from he absolue value of he area under he v- graph or direcly from he x- graph