Physics 207 Lecture 10

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Phyic 07 Lecure 0 MidTer I Phyic 07, Lecure 0, Oc. 9 Ex will be reurned in your nex dicuion ecion Regrde: Wrie down, on epre hee, wh you wn regrded nd why. Men: 64.6 Medin: 67 Sd. De.: 9.

1 Phyic 07 Lecure 0 MidTer I Phyic 07, Lecure 0, Oc. 9 Ex will be reurned in your nex dicuion ecion Regrde: Wrie down, on epre hee, wh you wn regrded nd why. Men: 64.6 Medin: 67 Sd. De.: 9.0 Rnge: High 00 Low 5 Soluion poed on hp://y.wic.edu Noinl cure (conerie): A B or A/B C or B/C rginl 5-35 D Below 5 Phyic 07: Lecure 0, Pg Phyic 07, Lecure 0, Oc. 9 Agend: Chper 7, Work nd Energy Trnfer Definiion of Work ( clr quniy) Vrible force deice (e.g., Hooke Lw pring) Work/Energy Theore W K Kineic Energy K / Power (on Wednedy) P dw / d Aignen: or Wednedy red Chper 8 WebAign Proble Se 4 due Tuedy nex week (r now) Phyic 07: Lecure 0, Pg Work & Energy One of he o iporn concep in phyic. Alernie pproch o echnic. Mny pplicion beyond echnic. Therodynic (oeen of he or pricle). Qunu echnic... Very ueful ool. You will lern copleenry pproch (ofen uch eier) wy o ole proble. Bu here i no free lunch.eier bu here re fewer deil h re explicily known. Energy Conerion Energy cnno be deroyed or creed. Ju chnged fro one for o noher. We y energy i conered! True for ny ioled ye. Doing work on n oherwie ioled ye will chnge i energy... Phyic 07: Lecure 0, Pg 3 Phyic 07: Lecure 0, Pg 4 Definiion of Work, The bic Ingredien: orce ( ), diplceen ( r ) Work, W, of conn force cing hrough diplceen r i: W r (Work i clr) Sclr or Do Produc r diplceen Work ell you oehing bou wh hppened on he ph! Did oehing do work on you? Did you do work on oehing? Siple ce (no fricionl force nd no non-conc force) Did your peed chnge? ( wh hppened o!!!) Phyic 07: Lecure 0, Pg 5 Reeber h ph eole wih ie nd ccelerion iplie force cing on n objec ph + nd ie 0 Two poible opion: Chnge in he gniude of Chnge in he direcion of ng + rdil ng + rdil 0 0 A ngeil force i he iporn one for work! How long (ie dependence) gie he kineic The dince oer which hi force Tng i pplied: Work Phyic 07: Lecure 0, Pg 6 Pge

2 Phyic 07 Lecure 0 Definiion of Work... Only he coponen of long he ph (i.e. diplceen ) doe work. The ecor do produc doe h uoiclly. Exple: Trin on rck. r co If we know he ngle he force ke wih he rck, he do produc gie u co nd r Phyic 07: Lecure 0, Pg 7 Reiew: Sclr Produc (or Do Produc) 7.3 Ueful for perforing projecion. A î A x Clculion i iple in er of coponen. A î A x A B (A x )(B x ) + (A y )(B y ) + (A z )(B z ) Clculion lo in er of gniude nd relie ngle. A B A B co You chooe he wy h work be for you! A y Phyic 07: Lecure 0, Pg 8 Work: -D D Exple (conn force) A force 0 N puhe box cro fricionle floor for dince 5. inih 0 Uni: orce x Dince Work Newon x Meer Joule [M][L] / [T] [L] [M][L] / [T] k cg Oher Work i A B A B co 0 x 5 N 50 J N i defined o be Joule nd hi i uni of energy Work reflec energy rnfer N- (Joule) Dyne-c (erg) 0-7 J BTU 054 J clorie 4.84 J foo-lb.356 J ev.6x0-9 J See exple 7-: Puhing runk. Phyic 07: Lecure 0, Pg 9 Phyic 07: Lecure 0, Pg 0 Work: -D D nd Exple (conn force) A force 0 N puhe box cro fricionle floor for dince 5. inih 80 Work: -D D 3 rd Exple (conn force) A force 0 N puhe box cro fricionle floor for dince 5. inih -45 Work i A B A B co (-) -0 x 5 N -50 J Work reflec energy rnfer Work i A B A B co x 0.7 N 35 J Work reflec energy rnfer See exple 7-: Puhing runk. Phyic 07: Lecure 0, Pg See exple 7-: Puhing runk. Phyic 07: Lecure 0, Pg Pge

3 Phyic 07 Lecure 0 Work nd Vrying orce Conider rying force (x) x x Tex : 7.3 Are x i increing Here W r becoe dw dx W inih ( x) dx 0 Lecure 0, Exercie Work in he preence of fricion nd non-conc force A box i pulled up rough (µ > 0) incline by ropepulley-weigh rrngeen hown below. How ny force re doing work on he box? Of hee which re poiie nd which re negie? Ue orce Body Digr Copre force nd ph (A) (B) 3 (C) 4 Work i clr, he cch i h here i no ie/poiion info on hnd Phyic 07: Lecure 0, Pg 3 Phyic 07: Lecure 0, Pg 4 Tex : 7.3 A rible force deice: A Hooke Lw Spring Spring re eerywhere, (probe icrocope, DNA, n effecie inercion beween o) Re or equilibriu poiion (work done on pring) In hi pring, he gniude of he force incree he pring i furher copreed ( diplceen). Hooke Lw, Acie igure S - k i he oun he pring i reched or copreed fro i reing poiion. Phyic 07: Lecure 0, Pg 5 Lecure 0, Exercie Hooke Lw Reeber Hooke Lw, x -k Wh re he uni for he conn k? kg kg kg kg (A) (B) (C) (D) i in kg / nd diiding by gie kg/ or N/ Phyic 07: Lecure 0, Pg 6 Lecure 0, Exercie 3 Hooke Lw Lecure 0, Exercie 3 Hooke Lw 8 c 8 c 9 c 9 c 0.50 kg Wh i he pring conn k? 0.50 kg pring Wh i he pring conn k? Σ 0 g k - g Ue k g/ 5 N / 0.0 (A) 50 N/ (B) 00 N/ (C) 400 N/ (D) 500 N/ Phyic 07: Lecure 0, Pg 7 (A) 50 N/ (B) 00 N/ (C) 400 N/ (D) 500 N/ g Phyic 07: Lecure 0, Pg 8 Pge 3

Phyic 07 Lecure 0 -x x relion for foo rch: -x x relion for ingle DNA olecule orce (N) Diplceen () Phyic 07: Lecure 0, Pg 9 Phyic 07: Lecure 0, Pg 0 Meureen echnique: opicl weezer Work & Kineic

4 Phyic 07 Lecure 0 -x x relion for foo rch: -x x relion for ingle DNA olecule orce (N) Diplceen () Phyic 07: Lecure 0, Pg 9 Phyic 07: Lecure 0, Pg 0 Meureen echnique: opicl weezer Work & Kineic Energy: Energy rnfer inoling chnge in peed A force, 0 N, puhe box cro fricionle floor for dince 5. The peed of he box i before he puh, nd fer he puh. Conider only hi force nd he box Rele he work o he kineic energy of he box i Phyic 07: Lecure 0, Pg Phyic 07: Lecure 0, Pg Work Kineic-Energy Theore: {Ne Work done on objec} {chnge in kineic energy of objec} W ne K K K See ex: 7-4 (finl iniil) Phyic 07: Lecure 0, Pg 3 Exple: Work Kineic-Energy Theore How uch will he pring copre (i.e. ) o bring he objec o op (i.e., 0 ) if he objec i oing iniilly conn elociy ( o ) on fricionle urfce hown below? o o pring n equilibriu poiion V0 pring copreed Noice h he pring force i oppoie o he diplcen. or he, work i negie or he pring, work i poiie Phyic 07: Lecure 0, Pg 4 Pge 4

5 Phyic 07 Lecure 0 Exple: Work Kineic-Energy Theore How uch will he pring copre (i.e. x f - x ) i o bring he objec o op (i.e., 0 ) if he objec i oing iniilly conn elociy ( o ) on fricionle urfce hown below? o o W box ( x) dx W box kx dx pring n equilibriu poiion W box - kx V0 pring copreed W box - k K - k 0 0 Phyic 07: Lecure 0, Pg 5 Lecure 0, Exercie 4 Kineic Energy To prcice your piching you ue wo bebll. The fir ie you hrow low cure nd clock he peed 50 ph (~5 /). The econd ie you go wih high he nd he rdr gun clock he pich 00 ph. Wh i he rio of he kineic energy of he f bll eru he cure bll? (A) /4 (B) / (C) (D) (E) 4 Phyic 07: Lecure 0, Pg 6 Lecure 0, Exercie 5 Work & ricion Two block hing nd where >. They re liding on fricionle floor nd he he e kineic energy when hey encouner long rough rech (i.e. µ > 0) which low he down o op. Which one will go frher before opping? Hin: How uch work doe fricion do on ech block? (A) (B) (C) They will go he e dince Phyic 07, Lecure 0, Recp Agend: Chper 7, Work nd Energy Trnfer Definiion of Work ( clr quniy) Vrible force deice (e.g., Hooke Lw pring) Work/Energy Theore W K Kineic Energy K / Power (on Wednedy) P dw / d Aignen: or Wednedy red Chper 8 WebAign Proble Se 4 due Tuedy nex week (r now) Phyic 07: Lecure 0, Pg 7 Phyic 07: Lecure 0, Pg 8 Pge 5

Forms of Energy. Mass = Energy. Page 1. SPH4U: Introduction to Work. Work & Energy. Particle Physics:

Forms of Energy. Mass = Energy. Page 1. SPH4U: Introduction to Work. Work & Energy. Particle Physics: SPH4U: Inroducion o ork ork & Energy ork & Energy Discussion Definiion Do Produc ork of consn force ork/kineic energy heore ork of uliple consn forces Coens One of he os iporn conceps in physics Alernive