PhysicsEveryday Phenomena I
PhysicsEveryday Phenomena I PHYS 103
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This 9 page Class Notes was uploaded by Sonny Breitenberg on Monday September 28, 2015. The Class Notes belongs to PHYS 103 at George Mason University taught by Staff in Fall. Since its upload, it has received 17 views. For similar materials see /class/215196/phys-103-george-mason-university in Physics 2 at George Mason University.
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Date Created: 09/28/15
PHYSICS 103 Lecture 18 Agmda fur Tuday Archmedes Pnnnple Example Pm lems Amhmedes Pnncxple An amen xmersed m 2 am Experiences an Llde buyunt fume equal m the waght nf m n msplaces An Object m a mm The dznmyafanydqmg ls Thls means um m msscmbe wn zn mpv Smce an mm dls aces m m whim af mdd1s means um n an mm 15 lass dams thaan mad 5 s nmzxgedm m bunyumcyfaxce ls gnatznhanns wugh Th2 mm w 1152 mm mm PHYSICS 103 Lecture 13 Agenda for Today Review of HW Momentum Impulse Conservation ofMomentum Collisions Momentum 39 Momentum is the product of mass times velocity of an object P m v 39 Momentum is a vector quantity same direction as v Units kg ms NEWTON S LAWS OF MOTION Second LAW The fence on an nbect ls equal to the product of at object39s mass times Its cceeato h acceleration Is In the same directoh as the fence 0 Fm a aAVAt IE Fm AVAt a F Atm Av Impuls At Apm Av Changein momentum NEWTON S LAWS OF MOTION Third LAW For every mroe that one object exets on a second ooeot there Is an equal but oppositey 39 oted oroe that the second ooect exets on the st ooeot g E For every action there is an equal but opposite reaction F At rri Av Ifthsextsmalfomsaw39nganasystsmofabjsctsbm the mlmonmmlsoonserwd CONSERVATION OF MOMENTUM Dun39ng a collision there are no external forces so momentum is ConSeW d This means total momentum before collision total momentum after collision Types of Collisions J quot Elastic 39 39 things bounce off each other Partially some kinetic energy is lost during Inelastic collisions Perfectly objects stick together Inelastic Example Collision Total momentum before collison Total momentum after collision v10ms VOmS Before After m39 10 mSkeme 2m 39 V Ltte This is an example ofan indas 39c collision Test your understanding A lkg can and a 2kg can roll tomrd the center of a straight tmk from opposite ends ofthe tmk each with a speed ofl ms A n e E 1 5 ms 1 ms 1 ms Before 2 kg 1 ms 1kg lmshetm 3 kg Weeds V V3 ms Example Problems Done in Class These are examples covering the topic speed 1 Elena has a one hour commute to school and she lives 20 miles away What is her average speed distance traveled 20 miles Average Speed 20 mph elaspsed time lhour 2 How fast does the moon go around the Earth The distance from the surface of the Earth to the moon is 238800 miles and the radius ofthe Earth is 6367 km The average speed is the total distance traveled divided by the time it takes to travel that distance We know that the moon takes one month 27 days to be precise to make one full circle around the earth The distance it travels is the circumference of the circle defined by its orbit If we call the radius of the orbit R then 2 238800 miles 39 161 Average Speed W E mlle m 2350mph elaspsed time t 27 days 24 houry day 3 How fast does the space shuttle go around the Earth The altitude of the space shuttle in orbit is about 200 miles ans 17 500 mph try working this one out 4 Practice for graphing motion Let us follow Erica s morning to school today i Erica gets in her car and goes 30 mph for 5 minutes to the nearest stop sign ii She realizes she forgets something makes an immediate U tum and goes 30 mph in the opposite direction back home for 5 minutes iii She searches for her textbook for 10 minutes in her house iv She then speeds at a constant speed of 100 mph for half an hour to make in time for class Draw a graph of velocity vs time Draw a graph of distance vs time How far away does Erica live What was her average velocity Erica s velocity vs time graph would look like this Velocity vs time for Erica39s Morning Velocity mph 1 o Time minutes To nd how far away she lives we would just nd the area under the graph For this we would need to calculate the areas of the three shaded rectangles Velocity vs time forMegan39s Morning Veloclty mph E Tlme minutes Which is 30 mph 5 minutes 30 mph 5minutes 100mph hours 50 miles PHYSICS 103 Lecture 3 Agenda for Today Motion unoler uniform acceleration Freely falling objects Acceleration due to gravity Hacking a falling object Description of Motion with Uniform Accleration Remember from last class that accelemtiorl is change in Velocity 7 AV elapsed time t 5 Average accelerati on If a is constant Where v final velocity vu initial velocity Example of Uniform Accleration A car accelerates at 3 rn from rest what is the final velocity a er 20 seconds We know vn0 ms a3 ms2 t20 s VWa 3 v03r 20560ms How far didit travel in this time Remember from last class that distance is distance traveled d time of travel t Average velocity rfaccelantton a is constant then 3 Va V If acceleration a IS constant then the final velocity v 15 given by v v at 1 vvnat so dvtjtvnt3atz Motion with Uniform Acceleration acceleration al velocity n Flnzl velarquot In Value alt lnmal v2 elncny at inter ream a e n v 1 aiii39m mquot Example Problems for Uniform Accleration 1 A car starts out at a velocity on ms Lfit39s acceleration is 3 msz how fast will it be going in 20 s 2 A car starts out at a velocity on ms Lfit39s acceleration is 3 msz how long will it take before it will be going oz m s 3 In the problem above how far will it have traveled 4A car starts out at a velocity on ms Ifits acceleration is 3 mi how long will it take the car to travel 540 m Fredy falhng am 215 WNW uname mwmumnm swank mm m zwmtmm mtmxmmmmm gm my 39I p f xmamx l wimvumwihmm mm Ab drvpyedfmmzzh bu dug u sure