8/31/11. the distance it travelled. The slope of the tangent to a curve in the position vs time graph for a particles motion gives:

Transcription

1 Physics 101 Tuesday Class 2 Chaper 2 Secions Displacemen and disance Velociy and speed acceleraion Reading Quiz The slope of he angen o a curve in he posiion vs ime graph for a paricles moion gives: A: The paricles speed B: The paricles acceleraion C: The paricles average velociy D: he paricles insananeous velociy E: wha are you alking abou, his wasnʼ par of he reading assignmen Eric Mazur, Peer Insrucion, 1997 Displacemen versus Disance, Quesion 2 An objec goes from one poin in space o anoher. Afer i arrives a is desinaion, is displacemen is: A) eiher greaer han or equal o B) always greaer han C) always equal o D) always smaller han or equal o E) eiher smaller or larger he disance i ravelled Displacemen versus Disance, Quesion 3 Does he displacemen of an objec depend on he specific locaion of he origin of he coordinae sysem? A) Yes B) No C) I depends on he coordinae sysem Follow up wha does your car odomeer measure? Eric Mazur, Peer Insrucion,

2 Displacemen versus Disance, Worked example 1 A person iniially a poin P in he graph below says here for a momen hen moves slowly along he axis o Q and says here for a momen. She hen runs quickly o R, says here for a momen, he srolls back o P. Draw a posiion vs ime graph ha describes his process. Q 1 m R 1 m Calculae he Disance raveled and he final displacemen P Eric Mazur, Peer Insrucion, 1997 Displacemen versus Disance, Quesion 1 sar: x1 x3 x end: x4 +50 Seve is pacing back and forh in lecure. He sars a x =+10 (measured in dm from he edge of he bench), moves righ o x=+30, moves back lef o +20, hen finally moves righ o +50, as shown. Wha is he disance ravelled, and he displacemen? A: +40, and +40 (dm) B: +60, and +40 (dm) C: +40, and +60 (dm) D: +60, and +60 (dm) E: Somehing else, none of he above. x Universiy of Colorado, 2004 Velociy and Speed Quesion 1 If he posiion of a car is zero, does is speed have o be zero? Velociy and speed quesion 2 The graph of posiion vs ime is shown below? Wha can you say abou he velociy of he car over ime A) Yes B) No X A) I speeds up all he ime B) I slows down all he ime C) Someimes i speeds up, someimes i slows down D) none of he above 2

3 Velociy and Speed Quesion 3 A person iniially a poin 3 on he x-axis says here for a lile while and hen srolls along he x-axis o poin 1, says here for a momen and hen runs o poin 2 and remains here. Velociy and Speed Quesion 4 As I walk, wha is my ypical speed? Which of he following graphs represens ha: A: 0.2 m/s B: 2.0 m/s C: 20 m/s D: Impossible - I need a calculaor... Velociy and speed quesion 5 The posiion vs ime graph for a car is shown below, which graph represens a car speeding up, hen slowing down and going backwards? A) x B) x C) x D) x Graphing posiion and velociy quesion 1 The graph shows posiion as a funcion of ime for wo rains running on parallel racks. Which is rue: x A b B A) a b, boh rains have he same velociy B) Boh rains speed up all he ime C) Boh rains have he same velociy a some ime before b D) Somewhere on he graph boh rains have he same acceleraion. 3

4 Graphing velociy and speed Quesion 2 Velociy and Speed Quesion 1 A person sars in Miami, drives o Pompano Beach, 50 km away, in 1 hours, surfs in Pompano Beach for 1 hour, hen speeds back o Miami in 30 minues. sar finish 50 km in 1 hour 50 km in 1/2 hour Pompano Beach Denver. (Wai 1 hour) Wha is he average speed of his complee rip (including sop)? A: zero B: 67 km/hr C: 40 km/hr D: 75 km/hr E: None of hese. Calculaing Velociy and Speed Quesion 1 A person sars in Miami, drives o Pompano Beach, 50 km away, in 1 hours, surfs in Pompano Beach for 1 hour, hen speeds back o Miami in 30 minues. sar finish 50 km in 1 hour 50 km in 1/2 hour Wha is he average velociy of his complee rip (including sop)? A: zero B: 67 km/hr C: 40 km/hr D: 75 km/hr Pompano Beach Denver. (Wai 1 hour) Calculaing Velociy and Speed Worked example 2 On your wedding day you leave for church 30 minues before he ceremony, which should be good as he church is only 10.0 miles away. On he way here is a consrucion sie, and you have o sop for awhile. Thus for he firs 15 minues you only average 5 miles/hour. Wha average speed do you need for he res of he rip o ge you o church on ime? E: None of hese. 4

5 Acceleraion Quesion 2 Acceleraion worked example 3 A je makes a landing raveling due Eas wih a speed of 100 m/s. If i comes o res in 10.0 s, wha is he magniude and direcion of i s average acceleraion? Acceleraion quesion 3 Acceleraion Quesion 4 A car is raveling due norh a 20.0 m/s. The velociy of he car afer 8 s if i s average acceleraion is 2 m/s 2 due souh is: A) 4 m/s Norh C) 8 m/s Souh B) 36 m/s Norh D) 12 m/s Norh Running a 10 m/s, a horse has an average acceleraion of -2.0 m/s 2. How long does i ake o reduce i s velociy o 4 m/s? A) 5 s B) 3 s C) 8 s D) never happens 5

6 Anonymous quesion Now ha we have done one session, which syle did you enjoy more: A) Liked his syle B) Liked his syle (alhough could use improvemen). C) Liked he firs lecure beer D) really wish I weren here a all. E) would raher have my fingernails pulled ou han aend eiher syle. 6

7

8

9