15210 RECORDING TIMER - AC STUDENT NAME:

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1 CONTENTS RECORDING TIMER - AC STUDENT NAME: REQUIRED ACCESSORIES o C-Clamps o Ruler or Meer Sick o Mass (200 g or larger) OPTIONAL ACCESSORIES o Ticker Tape Dispenser (#15225) o Consan Speed Vehicle ( #10-103) PURPOSE To produce a posiion versus ime record of moving objecs using a mechanical sriker and paper ape CONCEPT Timing evens is an essenial skill for many scienific invesigaions as well as oher pracical applicaions While many evens can be imed accuraely by using a sopwach, he recording imer provides capabiliies ha a sopwach canno achieve: The recording imer works in fixed ime inervals (1/60 or 1/50 second) The recording imer creaes a physical record of moion on a icker ape Analysis of recorded daa does no depend on hasily recorded values; daa from a icker ape can be measured and analyzed afer he compleion of an invesigaion In order o record imed evens successfully, pracice using he recording imer SAFETY This device runs on 110V, 60 Hz elecriciy from sandard household oules Observe normal safey precauions for any elecrical appliance To avoid elecrical shock, do no use near waer Do no use his device if i is damaged in any way Use appropriae eye proecion, as his device has rapidly vibraing pars ha can propel debris a high speeds Also, say clear of any areas where falling objecs may be used When invesigaing he acceleraion due o graviy, sand clear of he area direcly under he recording imer where weighs are being dropped Also, pick up weighs afer hey have been dropped, so ha hey do no presen a ripping hazard INTRODUCTION Recording he moion of a swifly moving objec cannon balls, falling rocks or flying birds, for example made some observaions very challenging for early scieniss During he 1600s Galileo observed and described he moion of falling objecs These observaions are essenial o undersanding physics, bu his accomplishmens were limied by he echnology of his day Galileo used simple pendulum-driven imers, his own pulse, and waer clocks o keep ime during his experimens The inabiliy o observe shor ime inervals also limied he observaions of Isaac Newon This difficuly, and problems of analyzing moion, led Newon o develop calculus of infiniesimals, a branch of mahemaics which focuses on infiniesimal inervals o calculae raes of change, as well as oher significan quaniies Wihou exremely accurae iming equipmen, modern advances such as communicaion saellies, air ravel, and global posiioning would be impossible Timing can now be accomplished using digial devices ha are accurae o millionhs of a second Phoogaes and oher auomaic riggers can sar and sop iming faser han a human can rip a sop wach SCIENCE FIRST Gene Lasserre Blvd, Yulee, FL wwwsciencefirscom info@sciencefirscom

2 This recording imer records inervals of 1/60 of a second (1/50 of a second in counries which use 50 Hz AC elecriciy) and provides a record of posiions on a paper ape For many lab projecs, he recording imer provides an easy-o-undersand record of moion wih far more deail han simple observaions can provide ASSEMBLY & SUGGESTIONS FOR USE Clamp he imer o a able op, ring sand, or oher sable suppor Place a carbon disc, carbon side down, over he pos in he base of he imer Slip he recording ape hrough he wo guides and under he sriker Make sure ha he paper ape ress under he carbon disc The ape should move freely hrough he recording imer The end of he paper ape can be aached o a variey of objecs o record he posiion of ha objec as a funcion of ime Velociy and acceleraion can be calculaed from his recorded daa Make sure he ape is drawn sraigh hrough he imer Avoid siuaions where he ape will be pulled o he side; his may cause he ape o cach or bind When he paper ape is properly loaded and a recording is abou o be made, urn he recording imer on by using he slide swich on he back of he uni, hen release he objec ha is o be imed The imer needs no calibraion, as i runs on 110V AC power The sriker will make a mark on he recording ape 60 imes each second (In counries ha use 50 Hz AC elecriciy, his imer will make a mark on he recording ape 50 imes a second In counries ha use AC elecriciy a a volage oher han 110V, a volage converer will be necessary #15210A is a recording imer which runs on 220V AC elecriciy) The clariy of he dos on he recording ape can be conrolled by adjusing he heigh of he sriker The cleares dos are obained when he sriker jus ouches he paper ape when in operaion To make his adjusmen, place he plasic feeler gauge beween he poin of he sriker and he base of he imer Loosen he wing-nus on he sriker and move hem up or down unil he sriker jus ouches he gauge Tighen he wing-nus afer calibraing he heigh of he sriker The posiion of he dos on he paper ape (from side o side) can be conrolled by loosening he wing-nus and sliding he sriker along he slo in he sriker arm When he desired locaion is reached, ighen he wing-nus This adjusmen will allow differen porions of he carbon disk o be used Afer iming an experimen, he recording ape provides a direc measure of posiion as a funcion of ime for a paricular objec Below is an example of a recording ape aken from an objec wih consan acceleraion In order o deermine he successive posiions of he objec, pick a saring poin on he recording ape o use as a reference (This is usually a poin near he beginning of he run Ofen, his reference poin is he firs poin ha can be clearly disinguished from he smudge ha he imer makes when i sars, bu he saring poin can be any arbirary posiion) Measure he disance from his reference poin o each poin marked on he ape by he recording imer If you are measuring many daa poins, you may wish o measure secions of 5, 10, or 20 inervals beween dos (I is ofen helpful o circle he poins on he ape ha are acually used for measuremen) Afer you have measured he disance from he reference poin o each seleced poin on he ape, record your posiion values (x 1, x 2, ec) in a daa able, such as he able shown on he nex page The ime for he saring poin is 0 = 0 The ime for each successive recorded poin is he number of spaces (n) beween ha poin and he saring poin divided by he frequency of your AC elecriciy (since he recording imer srikes he icker ape a he same frequency as your AC elecriciy) The velociy of he objec can be deermined by measuring he displacemen beween wo adjacen poins and dividing his displacemen by he ime inerval beween he wo poins (use he same ime inerval for all calculaions) Record hese values in he able in a column o he righ of he posiions The acceleraion of he objec can be deermined by calculaing he change in velociy beween wo adjacen able values and dividing his by he ime inerval beween he wo poins Record his new value in a column o he righ of he velociies Wih his able you now have a record of he posiion, velociy, and acceleraion of he objec as a funcion of ime Noice ha each calculaed quaniy has one less enry han he column before i SCIENCE FIRST Gene Lasserre Blvd, Yulee, FL wwwsciencefirscom info@sciencefirscom

3 TABLE FOR DATA COLLECTION For recording and analyzing daa from Recording Timer apes (See noes on nex page) Time Posiion Velociy ( = +1 - ) NO VALUE Acceleraion 0 =0 x 0 = NO VALUE v 1 =(x 1 -x 0 )/ 1 =n/60 x 1 = a 1 =(v 2 -v 1 )/ v 2 =(x 2 -x 1 )/ 2 =2n/60 x 2 = a 2 =(v 3 -v 2 )/ v 3 =(x 3 -x 2 )/ 3 =3n/60 x 3 = a 3 =(v 4 -v 3 )/ v 4 =(x 4 -x 3 )/ 4 =4n/60 x 4 = a 4 =(v 5 -v 4 )/ v 5 =(x 5 -x 4 )/ 5 =5n/60 x 5 = a 5 =(v 6 -v 5 )/ v 6 =(x 6 -x 5 )/ 6 =6n/60 x 6 = a 6 =(v 7 -v 6 )/ v 7 =(x 7 -x 6 )/ 7 =7n/60 x 7 = a 7 =(v 8 -v 7 )/ v 8 =(x 8 -x 7 )/ 8 =8n/60 x 8 = a 8 =(v 9 -v 8 )/ v 9 =(x 9 -x 8 )/ 9 =9n/60 x 9 = SCIENCE FIRST Gene Lasserre Blvd, Yulee, FL wwwsciencefirscom info@sciencefirscom

4 SUGGESTIONS FOR USE: DATA TABLE For he recording imer, he inerval beween srikes is 1/60 of a second, so ime is he number of spaces divided by 60 (Using 1/50 of a second in counries which use 50 Hz AC elecriciy, change each 60 in he Time column o a 50 ) In he Time column, n is a muliplier for he number of inervals beween srikes ha you choose o coun For example, if you coun displacemen on your icker ape as a span of five inervals beween srikes, hen n = 5 for your paricular daa se The saring poin for measuring displacemen (x 0 = 0) is a any do which can be clearly disinguished from he smudge of dos made by saring he imer, or any arbirary saring posiion on he ape ha is useful for your experimen In he Posiion column, record he disance of he do on he icker ape measured from he saring poin (a x 0 = 0) Speed is a change in displacemen divided by a change in ime (v = Δx/Δ) You mus have a leas wo posiion erms o calculae a velociy If you find i useful, you can noe he changes in displacemen, Δx, in he exra space under each Posiion value recorded as x 0, x 1, x 2, x 3, ec Noe ha speeds (velociies) ha are recorded are he average speeds calculaed for he ime inervals beween each lised ime We have no way o calculae speed before he firs change in displacemen, so NO VALUE is shown prior o v 1 Acceleraion is a change in velociy divided by a change in ime (a = Δv/Δ) You mus have a leas wo velociy erms o calculae an acceleraion If you find i useful, you can noe he changes in velociy, Δv, in he exra space under each Velociy value recorded as v 1, v 2, v 3, ec Acceleraions ha are recorded are average acceleraions calculaed for approximaely each of he lised imes We have no way o calculae acceleraion before he firs change in velociy, so NO VALUE is shown prior o a 1 PROCEDURE A (MEASURING CONSTANT VELOCITY) Preparaion and Procedure (1) Clamp a recording imer o a able or bench Feed a paper ape hrough he recording imer, and aach his paper ape o a Consan Speed Vehicle (CSV), or a similar device ha moves wih consan velociy Eliminae any possibiliy of obsrucing he paper ape (see Assembly and Operaion secion of his handou) Turn on he recording imer and sar he CSV Sop he vehicle when i approaches he end of he bench Afer sopping he CSV, rerieve and analyze your ape Q1 Does he paper ape indicae uniform speed for he vehicle? Explain To deermine he speed of he vehicle, find a segmen of seven dos ha show clearly uniform speed Measure he oal lengh of hese spaces Then, divide his measuremen by he ime inerval Q2 Wha ime inerval does his lengh represen? Q3 Wha is he speed of he vehicle? Preparaion and Procedure (2) The CSV can operae a wo differen speeds, depending on he number of baeries powering he vehicle If using he CSV, change he number of baeries used o power he Vehicle If you are no using he CSV, find a way o change he operaing speed of he apparaus you used in he previous segmen Se up he recording imer, paper ape, and vehicle as you did in he previous segmen Once you are ready o record daa, sar he recording imer and he CSV Sop he vehicle when necessary Afer sopping he CSV, rerieve and analyze your ape Q4 Does he paper ape show uniform speed for he vehicle? Wha is ha speed? Q5 How can you accoun for he difference in speed? SCIENCE FIRST Gene Lasserre Blvd, Yulee, FL wwwsciencefirscom info@sciencefirscom

5 PROCEDURE B (MEASURING ACCELERATION DUE TO GRAVITY) Suggesed Grade Level: Grades 5-12 Conen Area Focus: Velociy and Acceleraion (Linear Kinemaics) Preparaion and Procedure Clamp a recording imer o a suppor, and hang he recording imer over he edge of a bench or able When conducing his experimen, he paper ape mus fall verically hrough he guides Feed a piece of icker ape one meer long hrough he imer Aach a large mass (250 grams or more) o he icker ape, and hold he icker ape so ha he mass hangs jus below he recording imer Be sure ha he ape will fall hrough he imer wih lile fricion Sar he imer, and drop he mass Sop he imer once he objec reaches he floor and he ape has fallen hrough Examine he ape If any dos appear o be missing, repea his procedure If your daa appears o have no missing poins, measure he posiions of each of he dos, and calculae he velociy and acceleraion of he falling objec Q1 Does he objec appear o fall wih consan speed or wih acceleraion? How can you ell? Q2 If he objec acceleraed as i fell o he ground, wha is he value of ha acceleraion? If he objec fell wih consan speed, wha is ha speed? SCIENCE FIRST Gene Lasserre Blvd, Yulee, FL wwwsciencefirscom info@sciencefirscom