Class Note for NATS 101 at UA 3
Class Note for NATS 101 at UA 3
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Date Created: 02/06/15
Topic 7 Overview of Newton s Laws of Motion amp Momentum QUOTE FOR TODAY Mathematical and mechanical principles are the alphabet in which God wrote the world Robert Boyle STUDENT S FAVORITE QUOTES 10 00 w m w 2 D O a D q C L a Q E 2 p N 1 2 3 4 5 6 7 8 91011121314151617181920212223 Quotes MOST INTRIGUING or SURPRISING QUOTES Flat out winner was Quote 13 It is like nding the handwriting of God Trend The majority of students found it interesting that scientists who base their work on fact believe in something that has no proof ANOTHER QUOTE FOR TODAY If I ha ve seen farther than other men it is by standing on the shoulders of giants Sir Isaac Newton 16421 727 U 39 gLf Scholar 7 Advance 1 Sch c ar 332 a rch h nlar Preferences Stand on the ZSI39IC LJIFj39EIS of Eli m fza Granule Hume bum 13001159 Abram EBUMHE Schiller mat539 Go gle SCIENCE IS A CUMULATIVE ENTERPRISE A f x d Ex M1 g H mm ITquot We mam THE MQST Emil WILLS EVERCHANGING HE V I geehg mmn NATURE OF SCIENTIFIC HULLFT m Mini E AgarET rij 1F US u Father of Experimental science Isaac Newton 16421727 Newton later expressed many of Galileo s ideas observations and theories as formal laws which we know as THE LAWS OF MOTION SOME DEFINITIONS WE NEED Force F any influence that can cause a body to be accelerated The common force unit is the newton A force is an action not a thing Every force is similar to a push or a pull Net force the total overall force on an object If acting in the in the SAME direction the vector sum of the two forces gt gt gt If acting in the OPPOSITE direction the vector difference between the two forces gt lt gt Net force acts in the direction of the stronger force SOME DEFINITIONS WE NEED Inertia The tendency of a body to resist a change in motion or a body s ability to stay at rest or to maintain an unchanging velocity A body s INERTIA is its degree of resistance to acceleration in other words its MASS Mass the quantity of matter in a body a measurement of the inertia or sluggishness that a body p45 SOME DEFINITIONS WE NEED Mass vs weight Mass the quantity of matter in a body a measurement of the inertia or sluggishness that a body Weight The force due to gravity upon a body More specifically the net gravitational force exerted on it by all other bodies p45 The astronaut in space depicted at right finds itjust as difficult to shake the weightless anvil as it would be on earth Q1 If the anvil is more massive than the astronaut which shakes more anvil yafufr ANSWER 2 the astronaut Explain your answer using the terms mass and inertia Both the anvil and astronaut are weightless but the anvil as more hence the anvil has mere i inegrtia shea less p 39 1 st Law of Motion Law of Inertia A moving object will continue moving in a straight line at a constant speed and a stationary object will remain at rest unless acted on by an unbalanced force Other ways of stating Law 1 Every body continues in its state of rest or of uniform motion in a straight line unless it is compelled to change that state by forces impressed upon it MH text 0 All bodies have inertia Newton s Laws in everyday life Wise 8 Lance Aldrich Mar 539sz HON I 60739 4 QO ICK GUMUse CJF THE GROCERIES As 7H6 P455517 M6quot AND SMMMED mm THC DA SH 0016 74626 6055 77 cums om Every so often Newton39s Laws of Motion rear their ugiy heads EASY WA Yof remembering the 13 Law The key word is quotcontinuequot If a body is at rest it continues to stay at rest if moving it continues to move in a straight line It can t start or stop moving on its own without some external force ie quota body does not accelerate itselfquot p45 2nd Law of Motion Newton s Law of Motion The acceleration a produced on a body by a force F is proportional to the magnitude of the force F and inversely proportional to the mass m of the object aFlm or Fma 2Incl Law F ma Acceleration 0C net force mass 0C quotis proportional toquot or a oc Fm a Fm with appropriate units of m32 for a ne wtons for F kilograms for m FORCE OF HAND ACCELERATES THE BECK TWICE AS MUCH RJRCE PRODUCES macs AS MUCH AmELERATION THE SAME FORCE ACCELERATE S 2 BRICKS AS MUCH TWICE THE FORCE 0N TWICE THE MASS ENES THE SAME FORCE 3 BRICKSAS ACCE LERATE s 2 BRICKS MUCH ACCELERATION CHOICES FOR ABOVE CHOICES FOR ABOVE A1m D3 nms 18 tWice E39 6 tim IGw3 F1B THE SAME FORCE 3 BRICKSAS ACCE LERATE s 2 BRICKS MUCH ACCELERATION CHOICES FOR ABOVE CHOICES FOR ABOVE A 12 1 s D 339 times 18 tWice E39 6 tim 13 F 3rd Law of Motion Law of Force Pairs For every action there is an equal and opposite reaction 3rd Law Law of Force Pairs Forces always occur in pairs an action and a reaction 39I39o every action force there is an equal and opposite reaction force whenever one body exerts a force on a second body the second body exerts an equal and opposite force on the rst body The two forces are equal in strength but opposite in direction There is never only a single force in any situation p46 ACTION Man pulls on spring REACTION pulls on String pulls on man p46 2quotCI law reminds that mass is involved Remember this quote Newton 39s passage from a falling apple to a falling moon was an act of the prepared imagination 39quot7 V5 L xii x u John Tyndall 1820 1893 Inspiration emerges from a wellinformed mind Isaac Newton s Apple Tree in Lincolnshire England NEWTON S INSPIRATION apple amp moon Earth pulls on apple gravity but THE APPLE ALSO PULLS ON THE EARTH Force by so small it cannot be applet arth measured but it is there 9 Newton likened the force pairs amp One more concept Momentum inertia in motion or more specifically the product of mass of an object and its velocity Momentum mass x velocity or Pmv To change the momentum of something requires force and time How LONG THE FORCE ACTS Force time interval IMPULSE IMPULSE Ft changes momentum Force time interval change in mass X velocity Ft change in mv an external force is required to change the momentum of a body Take notes Principle of Conservation of Momentum When m external net force acts on an object or a system of objects no change of momentum takes place No external net force no change in momentum Hence the momentum BEFORE the event involving internal forces is equal to the momentum AFTER the event Quick Review Forms of Energy Kinetic KE or KinE energy of motion the ability of a mass to do work KE 12 mass x velocity2 or KinE 12 ms 2 Potential PE energy a system possess if it is capable of doing work but is not doing work now Includes gravitational elastic chemical electrical and magnetic Understanding Car Crashes It s Basic Physics As you watch the video fill in the blanks on pp 4748 in CLASS NOTES G3 YOUR CAR amp GLOBAL CHANGE Part 1 SAFETY vs ENVIRONMENT What kind of car do you drive Dr H and her hummer 99999999999 Wow Six SUVs in a row Is this a ski resort or hunting lodge Noit39s a suburban apartment complex in FLORIDA Spud quotHIM A Widening Gap The fatality rates for occupants Fatality Rates for ei all vehicles involved in occupants of a crashes have declined in recent years but the gap between the vehicles involved in topselling categories sport crashes utility vehicles and cars has I L increased deaths per 100000 vehicles 39 39 Figums rs deaths for each 100000 reglstarad vehicles t l l 94 3995 96 9 98 3999 DD 01 3902 03 SaumNaifanaJHiighway W aff c Safer Admhfsl mtfon GLOBAL CHANGE LINK For every gallon of gas you use you add 22 pounds of CO2 to the atmosphere Recall Newton s 1st and 2nd Laws Now consider the mass and acceleration capabilities of a large SUV sport utility vehicle vs a small sedan and answer the following Q3 An SUV and a small sedan are both at rest at a stop light Which vehicle has a greater inertia Q3 Choices 1 The SUV has a greater inertia because it has a greater mass and resistance to acceleration 2 The sedan has a greater inertia because it has a greater ability to accelerate 3 Since both are at rest their inertia is the same Q3 An SUV and a small sedan are both at rest at a stop light Which vehicle has a greater inertia 1 The SUV has a greater inertia because it has a greater mass and resistance to acceleration 2 The sedan has a greater inertia because it has a greater ability to accelerate 3 Since both are at rest their inertia is the same Q4 If the mass of the SUV is three times that of the sedan the same amount of force via consumption of gasoline will accelerate the SUV as much as the sedan all other things being equal in the two engine designs Q4 Choices 1 3 times 2 13 4 3 nine times Now imagine that the two vehicles are moving down the freeway side by side at equal velocities of 75 mph Suddenly after rounding a curve the drivers encounter a large semitruck at a standstill that has jacknifed across both lanes If the two vehicles have comparable brakes which one is most in danger of smashing into the truck ahead Explain why using the term momentum CLASS DISCUSSION BACKGROUND Many people own SUVs because they feel safer in them and personal safety for oneself and one s family is clearly an extremely important consideration when buying a vehicle At the same time some SUV s have notoriously low gas mileage and hence contribute much more CO2 to the atmosphere than smaller and more fuel efficient cars For years SUV s pickups amp minivans were held to less stringent emissions controls than regular passenger cars In March 2006 the government finalized new regulations for SUVs minivans and pickup trucks calling for modest improvements in fuel efficiency in SUVs pickups and minivans CAFE Corporate Average Fuel Economy 1975 Energy Policy and Conservation Act of 1975 established Corporate Average Fuel Economy CAFE standards for passenger cars and light trucks passed in response to the 197374 Arab oil embargo stated nearterm goal was to double new car fuel economy by 1985 passenger cars amp light trucks required to meet CAFE standards standards applies on a fleetwide basis for each manufacturer entire line of passenger cars avg 275 mpg light trucks including vans amp SUVs avg 207 mpg 200304 manufacturers earn quotcreditsquot for exceeding CAFE standards can be used to offset fuel economy shortfalls over 3 model yrs Total fleet fuel economy peaked in 1987 at 262 mpg when light trucks made up a mere 281 percent of the market In 2004 light trucks made up more than 50 percent of new vehicle sales A1 pi tug 14x AM i rt 1 f 1quotquotiquot39ll I l 39739 tit114quot y 1 l39 3939 quot I quotI I F 0 quot Ll39 Passenger Cars 0 Domestic 1 Import I PASSENGER CAR CAFE I llJVIIJ 9C 92 94 9E 95 2000 2002 2004 91 93 95 97 3999 2001 2003 MODEL YEAR k 11 A I l liI l i itlfl 1 I IlliI I I Il I I l39 LIGHT TRUCK CAFE l Light Trucks 0 Other 39t Captive Import l l J l J 1 l I 39 I l 86 BB 90 92 94 BE 98 2000 2002 2004 39 95 97 99 2001 2093 April 2003 National Highway Traffic Safety Administration promulgated a final rule establishing the average fuel economy standards for light trucks that will be manufactured in the 20052007 model years MYs The 2003 standards for all light trucks manufactured were set at 210 mpg for MY 2005 216 mpg for MY 2006 222 mpg for MY 2007 See httpwwwfueleconomygovl New Reformed standards put forward in Mar 2006 httplwwwnhtsadotqovportallsitelnhtsalmenuitemd0b5a45b55bfbe58i 2f57529cdba046a0 MY 2008 From 268 mpg for the smallest vehicles to 204 mpg for the largest MY 2009 From 274 mpg for the smallest vehicles to 2l0 mpg for the largest MY 2010 From 278 mpg for the smallest vehicles to 208 mpg for the largest IVIY 2011 From 284 mpg for the smallest vehicles to 2l3 111pg for the largest Claimed Differences Between the Proposed and Final CAFE Light Truck Rule Proposed CAFE Light Truck Rule August 2005 Final CAFE Light Truck Rule March 2006 quotSixquot Size Categories With Their Own Miles Per Gallon Target Stronger Miles Per Gallon Target for All Light Trucks Largest SUVs Not Included Largest SUVs Included Average Miles Per Gallon 24 Average Miles Per Gallon 241 24 with Largest SUVs included 9 Billion Gallons of Fuel Saved 107 Billion Gallons of Fuel Saved QUESTION Is it environmentally irresponsible to own an SUV or pickup truck that gets mileage of LESS than 2021 mpg t Tony Cl39ft Blan kley John McLauthn 1 Mort Buchanan Zuckennan McLaughlin s Question Suppose the traffic accident mortality rate goes up because cars are made smaller to preserve fuel Is that a good tradeoff bodies for barrels 63 Part A will take place in your groups after the GROUP TEST on Thursday Sept 14 GO McLaughlin Group DISCUSSION QUESTION 1 Is it environmentally irresponsible to own an SUV or pickup truck that gets mileage of LESS than 20 mpg Yes or No amp whywhy not QUESTION 2 Suppose the traf c accident mortality rate goes up because cars are made smaller to preserve fuel Is that a good tradeoff Yes or No amp whywhy not QUESTION 3 Frame your group39s OWN Question answer it amp discuss it
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