Inroducion o LoggerPro Sr/Sop collecion Define zero Se d collecion prmeers Auoscle D Browser Open file Sensor seup window To sr d collecion, click he green Collec buon on he ool br. There is dely of second or wo before d collecion srs, so don ry o ime clicking he buon wih your cions. Mny prmeers in he sofwre re djusble, like he smple collecion ime. Adjusing hem is done hrough he menus, bu some common commnds nd prmeers re ilble hrough he oolbr. For emple, click he clock icon o chnge he smple re or ime. Ofen you will be old o lod/open file. Such files will se ll he relen prmeers for he eperimen. Grph prmeers cn be chnged by clicking on he grph o selec i nd using he menus, or by righ-clicking on he grph. Common grph commnds include zoom nd uoscle. If you cn see your d (he grphs pper blnk) or he d is fl line zero you probbly need o djus he grph scling. Sr wih Auoscle from 0, hen zoom-in or djus he es. If he collec buon is gry nd cn be clicked hen here my be problem wih he sensor hrdwre. Mke sure he cble o he sensor is snpped in plce nd likewise wih he cbles going o he inerfce bo. (The cble from he sensor goes o he inerfce bo; jus follow i.) If he buon is sill gry, he problem migh be he sofwre. Qui ou of LoggerPro nd resr i. If ll else fils, sk your lb insrucor for help. ii
Eperimen I 1-D Kinemics The d collecion for his nd mny oher lbs use LoggerPro sofwre opering riey of sensors conneced o LbPro inerfce. This week s sensor is Vernier Moion Deecor 2. I mesures posiion by emiing pulses of sound nd mesuring he ime unil he refleced sound reurns (like rdr bu wih sound wes). You will her clicking sound when d collecion begins. The deecion zone eends bou 15-20 o eiher side of he is of he bem s cenerline. If some oher objec or body pr ges inside his cone i will be deeced insed of he rge. A shrp chnge in he posiion d my be due o his. The posiion deecor cn mesure n objec only wihin he rnge 15 cm - 6 m. The deecor folds open so h he deecor cn be imed. Opening he deecor reels sensiiiy swich wih cr nd norml (person/bll) seings. Selecing he pproprie seing will gie beer d. The deful is for he posiion deecor o be he origin or he zero poin of n is wih he posiie direcion wy from he deecor. The only hing h is direcly mesured is posiion wih respec o he deecor s funcion of ime; he LoggerPro sofwre clcules he elociy nd ccelerion from he posiion d. This increses he noise in deried lues like ccelerion. Aciiy 1 Pu he deecor ino he firs seup: mesuring he cr on he rck. Open he file 1-D Kinemics #1 ; his file will iniilize some prmeers nd prepre grphs. Leel he rck so h he cr remins moionless or nerly moionless on he rck. Try undersnding he grphs for some smple moions. In priculr, mke sure you cn eplin he feures of he () grph nd how i reles o he () nd () grphs. The following re emples of siuions you cn ry: The cr ress moionless some disnce from he deecor. Afer d collecion srs, p he cr so h i moes slowly wy from he deecor. Cn you idenify when he p sred nd when i ended? Push he cr sedily o ge roughly consn ccelerion (difficul). Push he cr bck nd forh o ge oscillory moion. Cn you idenify he sign of he ccelerion s i chnges simply by looking ()? A ()? 1-D Kinemics I - 1
Aciiy 2 For ech cse below, (1) skech your bes guess for he cr s moion on he grphs, hen (2) perform he eperimen, idelly recording he eperimenl resuls in differen color nd (3) reconcile ny differences. 1. Rise one end of he rck o be bou 6 cm boe he oher. Plce he deecor he lower end nd he cr ner he higher end nd relese he cr. 2. Pu he deecor he higher end, wih he cr lso ner he higher end, nd relese he cr. 3. Wih he deecor he higher end, sr wih he cr ner he lower end nd p i so h i rolls owrds he deecor, sops before hiing he deecor nd hen rolls bck. You my need o prcice few imes before performing he mesuremen. (1) (2) (3) 1-D Kinemics I - 2
Aciiy 3 Predic he moion of he dropped bskebll. The posiion deecor will mesure he bll s moion fer you drop he bll. The bll will fll nd bounce firs ime nd hen bounce second ime while sill under he deecor. Your job is o predic he moion sring immediely fer he firs bounce nd coninuing unil jus before he second. Open he file 1-D Kinemics #2. Hold he deecor oer he floor, poining downwrd. Which wy is he posiie direcion? Mke your predicion on he lefmos grphs. Once you re redy o do he eperimen, wi for your insrucor. Do no drop he bskebll wih he compuer king d unil you he your insrucor s enion. Skech he resuls using he middle grphs below. Skech only he porion of he moion beween he firs nd second bounces. Predicion Mesured Use hese grphs for scrch work. 1 s bounce 2 nd bounce Insrucor Iniils: De: 1-D Kinemics I - 3
1-D Kinemics (1) Consider he grphs below. Fill in he ble wheher is posiie or negie nd wheher he objec is speeding up or slowing down. < 0 #1 #2 > 0 #3 #4 Poin Sign of Sign of #1 - + #2 - - #3 + - #4 + + Speeding up or slowing down? (2) You cn use he sign of he ccelerion lone o deermine if pricle is speeding up or slowing down. Using he ble h you jus filled ou, deelop rule o deermine if pricle is speeding up? (3) In fron of you re ril sloping upwrds nd cr. Le s use he coordine sysem shown in he figure. Tp he cr so h i rolls mos of he wy up before rolling bck down. To nswer hese ne wo quesions, use wh you see before you bu, lso, use he rule h you esblished boe. During he upwrd journey, wh is he sign of he elociy nd he ccelerion? How bou he downwrd journey? Workshees 1
(4) The posiion-ersus-ime grph shows he moion of objecs A nd B moing long he sme is. ) A = 1s is he speed of A greer hn, less hn or equl o he speed of B? (mm) 6 5 4 3 A A = 5s? b) A = 4s is he ccelerion of B negie, zero or posiie? 2 1 0 0 1 2 3 4 5 6 7 B (s) A = 6 s? c) A wh ime (roughly) re hey closes o ech oher? d) Does A eer urn round (reerse direcion)? Does B? (5) Ech of he following pirs of grphs shows kinemicl quniy ( or or ) ersus ime on he op grph. Skech plo of he indiced kinemicl quniy ersus ime on he boom grph. The dshed lines re gien for your conenience o help you line up imporn feures in he grphs. Workshees 2
(6) A mining cr srs from res he op of hill, rolls down he hill, oer shor fl secion, hen bck up noher hill, s shown in he digrm. Assume h he fricion beween he wheels nd he rils is negligible. Sign conenion: For ech secion of rck, le he direcion shown in he figure boe be ken s posiie. ) Which grph below bes represens he posiion-ersus-ime grph? b) Which grph bes represens he insnneous elociy-ersus-ime grph? c) Which grph bes represens he insnneous ccelerion-ersus-ime grph? Workshees 3
(7) Imgine rocke ship h moes in one dimension long he -is ccording o he equion: () = -6.0 + 1.5 + 0.50 2 = 1 s -8-7 -6-5 -4-3 -2-1 0 = 3 s 1 2 3 4 5 (cm) Here () is gien in cm nd is in seconds. All equions mus obey cerin rules or hey re meningless. Two imporn rules regrding unis re [1] boh sides of n equion mus he he sme unis (i mkes no sense o sy 2 meers = 4 seconds) nd [2] ny wo erms h re dded ogeher mus he he sme unis (i mkes no sense o elue 2 meers + 4 seconds). ) These rules ell us h, for he boe equion o mke sense, he numbers in i re no pure numbers bu re physicl quniies wih unis. Find he unis: -6.0 1.5 0.50 Noe h if, for emple, =, hen here is n implied 1 muliplying he h hs unis. b) Skech he grph of he posiion of he rocke ship beween = -3 s nd = 3 s. c) Find he displcemen of he rocke ship beween = 1 s nd = 3 s. Workshees 4
d) Find he erge elociy beween = 1 s nd = 3 s. We do no define e = ( i + f )/2. This equion migh yield he sme resul for he erge elociy s he one boe, bu in generl i does no. e) Find he elociy () = d/d ime = 1 s. Physiciss he precise definiion for he word speed h migh be differen from wh you he in mind. speed = erge speed = he mgniude (or bsolue lue) of he elociy ol disnce reled diided by ime inerl If you run o he lef nd hen bck o he righ, sopping where you sred, your erge speed is non-zero nd posiie, bu your erge elociy is zero. f) Find he speed ime = -1 s. g) Find he erge elociy beween = -3 s nd = 0 s. h) Find he erge speed beween = -3 s nd = 0 s. i) Find he ccelerion ime = -1 s. Workshees 5