Physic 231 Lecture 4. Mi it ftd l t. Main points of today s lecture: Example: addition of velocities Trajectories of objects in 2 = =

Size: px

Start display at page:

Download "Physic 231 Lecture 4. Mi it ftd l t. Main points of today s lecture: Example: addition of velocities Trajectories of objects in 2 = ="

Rosanna Foster
5 years ago
Views:

1 Mi i fd l Phsic 3 Lecure 4 Min poins of od s lecure: Emple: ddiion of elociies Trjecories of objecs in dimensions: dimensions: g 9.8m/s downwrds ( ) g o g g

2 Emple: A foobll pler runs he pern gien in he drwing b he hree displcemen ecors A, B nd C. The mgniudes of hese ecors re A5 m, B5 m, nd C8 m. Using he componen mehod, find he mgniude nd direcion of he resuln ecor ABC. lbel -comp -comp A 5 m B 5 m C m R 9.7m -5.3,m 53 R C 8m cos(35 ) 4.7m; C 8msin(35 ).3m; R m n( θ ) 5.3/9.7 θ.

3 quiz Bob rels 3 km due es nd hen rels 4 km due norh. Relie o his sring posiion wh is he mgniude of his ol displcemen nd he ngle wih respec o due es? ) )7k km, 35degrees o he souh of fdue es. b) 7 km, 53 degrees o he norh of due es c) 5 km, 35 degrees o he souh of due es d) 5 km, 53 degrees o he norh of due es ecor comp. comp. R B A 3 km B 4 km A R 3k km 4k km R R R 3 4 5km nθ R R o , norh of due es

4 relie eloci problems Lbl Lbel ech objec b leer l h hreminds id ou of wh hii is (for emple p for pper, g for ground, for ruck). Look for phses such s "he eloci of he pper relie o ruck" nd wrie he eloci s: pper _ relie _ o _ ruck p Tke he hree elociies nd ssemble hem ino n equion such s; pg g p S l f h l i N h h l ii d b Sole for he eloci ou wn. Noe h hese elociies need no be prllel. You m need o sole wo equions, one in he direcion nd noher in he direcion.

5 eercise Chuck looks hed nd sees Grndp Hrper. He hrows him newspper oer he op of he hood o him. The ruck is moing 4 km/hr due Wes. Relie o he ruck, he newspper lso moes Wes wih eloci of 4 km/hr. Wh is he eloci of he newspper relie o Grndp Hrper? ) km/hr pper _ relie _ o _ ground b) 8 km/hr due wes c) 8 km/hr due es ruck pper _ relie _ o _ ruck d) don know pper pp _ relie _ o _ ground km/hr Wes ruck pper relie o ruck 4 km/hr Wes 4 km/hr Wes pper relie o ground?

6 Emple norh Af ferr bo is reling in direcion o norh of es wih speed of 5. m/s relie o he wer. A pssenger is wlking wih eloci of.7 m/s due es relie o he bo. Wh is he eloci (mgniude nd direcion) of he pssenger wih respec o he wer? pb.7 m/s pw pb bw bw, ( ) es 5.cos(35. ) 4.9m / s bw, 5.sin(35. ).94m / s mg θ pb.7.7 bw pw pw m / s θ 35. o ( 94 ) θ n.94 3 norh of es pb.7 m/s 6.9

7 Projecile moion in wo dimensions g ( ) g o ( ) o g g hi h h f h l i i h This mens h he -componen of he eloci remins consn. The -componen reflecs he griionl ccelerion. This is rue; conrr o he presenion of Json below:

8 Projecile Moion The horizonl moion is consn; he ericl moion is free fll: The horizonl nd ericl componens of he moion re independen. Slide 3-37

9 emple A bulle is fired from rifle h is held.6 m boe he ground in horizonl posiion. The iniil speed of he bulle is m/s. Find () he ime i kes for he bulle o srike he ground nd (b) he horizonl disnce reled b he bulle. If upwrd is he direcion of posiie : m/s -.6 m

10 clicker quesion The digrm below shows wo successie posiions of pricle; i's segmen of full moion digrm. Which of he following ecors bes represens he ccelerion beween nd i f ) b) c) d)

11 emple A smll cn is hnging from he ceiling. A rifle is imed direcl he cn, s he figure illusres. A he insn he gun if fired, he cn is relesed. Ignore ir resisnce nd show h he bulle will lws srike he cn, regrdless of he iniil speed of he bulle. Assume h he bulle srikes he cn before he cn reches he ground. gri cn θ

12 Reding Quiz. The ccelerion ecor of pricle in projecile moion A. poins long he ph of he pricle. B. is direced horizonll. C. nishes ih he pricle s il highes hih poin. i D. is direced down ll imes. E. is zero. Slide 3-9

13 emple A moorccle dredeil is emping o jump cross s mn buses s possible (see he drwing). The keoff rmp mkes n ngle of 8. boe he horizonl, nd he lnding rmp is idenicl o he keoff rmp. Thebuses re prked side b side, nd ech bus is.74 m wide. The cclis lees he rmp wih speed of 33.5 m/s. Wh is he mimum number of buses oer which he cclis cn jump? 33.5 m/s.74m 33.5 m/s ) g θ 8 ( ) o b) o c) d) Which equion o use? g g 33.5sin(8 ).35m / s g g.s g 33.5cos(8 )(.s) 67.5m 67.5m Nbuses 4.5 4buses w.74m bus

14 Concep problem A bleship simulneousl fires wo shells enem ships. If he shells follow he prbolic rjecories shown, which ship ges hi firs? ) A b) boh he sme ime c). B d) need more informion iniil ericl eloci for A eceeds he iniil ericl eloci for B :, op o gh gh; h A > h B, A > o go o compring he wo rjecories : > >, A, B o, A o, B, B g

2D Motion WS. A horizontally launched projectile s initial vertical velocity is zero. Solve the following problems with this information.

2D Motion WS. A horizontally launched projectile s initial vertical velocity is zero. Solve the following problems with this information. Nme D Moion WS The equions of moion h rele o projeciles were discussed in he Projecile Moion Anlsis Acii. ou found h projecile moes wih consn eloci in he horizonl direcion nd consn ccelerion in he ericl