1、Motion in One DimensionKey TerminologyDistance SpeedTime*These are all scalar quantities-only magnitudeDisplacementVelocityAcceleration *These are all vector quantities-magnitude and directionDistance vs. Displacement DISTANCETotal traveledPath dependentScalar quantity Both use the same variable and
2、 unitsVariable: d (sometimes: x,r,)Units: mDISPLACEMENTChange in positionPath independentVector quantityCheck your understandingAn odometer in your car shows:Distance ExampleThe following is a list of gains and loses of a Bears possession First down: gain 8 yardsPenalty lose 10 yardsSecond down: gai
3、n 11 yardsThird down: lose 1 yardWhat is the total distance?What is the total displacement?Speed vs. Velocity DIFFERENCESSpeed: how fast (scalar)Always positiveExample: 25 m/sVelocity: how fast in a certain direction (vector)Can be positive or negativeExample: 25 m/s NorthSIMILARITIESVariable: vUnit
4、s: m/sCheck your UnderstandingA speedometer in your car shows:SpeedCheck your understandingJim travels from Palatine to Chicago at 65 mph. Susie travels from Chicago to Palatine at 65 mph. Are the velocities equal?No, different directionsFirst Equation!v=(df-di)/(tf-ti)OR commonly written asv=d/ t*
5、means changeAverage Speed/VelocitySample ProblemIn gym, you have to run the 100 m dash. If you run it in 18 s, what was your velocity?Sample ProblemA freaky fast Jimmy Johns delivery man makes a delivery that is 2.2 miles away and it takes him 9 min. What is his average velocity in mi/hr? Technical
6、difference between calculating speed and velocity:SPEED (AVERAGE)Total distance traveled divided by the total time elapsed*Example: Round trip drive to schoolVELOCITYTotal displacement divided by total timeA change in velocity Vector quantity Positive vs. Negative Acceleration+ velocity and + accele
7、ration = _+ velocity and - acceleration = _ - velocity and - acceleration = _- velocity and + acceleration = _Variable: aUnits: m/s/s or m/s2Equation:a=(vf-vi)/(tf-ti)OR commonly written as:a= v/ tAccelerationCheck your understandingName 3 ways to accelerate your car:Step on gas pedalStep on brake p
8、edalTurn steering wheelSample ProblemA car accelerates from a stop sign up to a speed of 11 m/s. If it takes 4 to do so, what is the cars acceleration?Velocity and Acceleration Sample ProblemsProblem 1:How long does it take a turtle to travel 1,000 m if it can travel at a pace of 1.3 m/s?Problems 2:
9、What is the change in velocity if an object accelerates at 2 m/s2 for 4.5 seconds? If the object started at 3 m/s, what is its final speed?Motion GraphsDISTANCE VS. TIME GRAPHSVELOCITY VS. TIME GRAPHSSlope is accelerationSlope = rise/run = velocity/time = ACCELERATION Area under graph is distance tr
10、aveledArea = base*height = velocity*time = DistanceSlope is velocitySlope = rise/run = distance/time = VelocityGeneral Graph TrendsStraight Lines CONSTANTCurving Lines CHANGINGFlat Line - ZEROSteeper the slope, the higher the valueWhat can you tell me about acceleration on these graphs?Big 5 Equatio
11、nsDefinition of average velocity: (vi + vf)/2Distance = rate * time: d=vavg*tDefinition of acceleration (final velocity): vf=vi + atTimeless: vf2=vi2 +2adPosition: d=vit +1/2at2Checklist for SuccessEquationxvivftaDefinition of average velocity: vavg=(vi + vf)/2Distance = rate * time:x=vavg*tDefiniti
12、on of acceleration (final velocity): vf=vi + atTimeless:vf2=vi2 +2axPosition:x=vit +1/2at2Problem Solving Strategies Identify givensLook for hidden givensIdentify unknown(s)Compare givens and unknowns to equationsIn the beginning: chartRe-read problem if stuck*always show your work (G.U.E.S.S.)Sampl
13、e ProblemWhat is Starlin Castros acceleration as he runs toward first base if he reaches the base with a speed of 6.5 m/s? The distance between the plates is 27.432 meters .Sample Problem #2An airplane can accelerate at a rate of 4.9m/s2. If it takes 45 s for the plane to start to elevate and the pl
14、ane starts from rest, what is the minimum length of runway required?Stopping Distance SampleSeeing a stop sign ahead, a person begins to brake as they drive lawfully on Cunningham. If their reaction time is 1 s, what is the total distance they need to stop if they can accelerate at -8 m/s2?谢谢你的阅读v知识就是财富v丰富你的人生
