Phys 201 1nd Edition Lecture 1 Outline of Current Lecture I. MotionA. How to describe itII. SpeedIII. DisplacementA. Difference between distance and displacementIV. VelocityA. Average and InstantaneousB. Graphical RepresentationV. Acceleration Current LectureMotion: Can be described in textual forms as moving in a given direction, a given distance, in a given amount of time. Physics uses graphs and diagrams to replicate motion, while using equations to make quantitative predictions about the motion.Speed: defined as the distance traveled by an object, divided by the time it took to travel that distance (S= d/t). Because distance and time are always a positive value, speed is also always a positive value.Example: If I walk 20 feet in 10 seconds, then my speed can be determined as S=20f/10s = 2f/s. Displacement: defined as the quantitative change in position. Displacement is the distance an object is from its original starting point. However, displacement and distance are not the same. Displacement is based on position, and therefore can be positive or negative. The easiest way tocalculate displacement is to subtract the distance traveled in one direction, from the distance traveled in the opposite direction. To determine if the distance is positive or negative, imagine your starting point as a 0 on a number line. Whether your displacement is positive or negative depends on whether you end up in front of the 0 on the number line, or behind it.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Example: If you travel two feet North, then three feet South, you have traveled a distance of 5 feet, but your displacement would be -1 feet (+2 - 3= -1). On the other hand, if you traveled 4 feet West, then traveled 6 feet east, your displacement would be 2 feet(-4 + 6= 2).Velocity: defined as a change in distance(or displacement) over a change in time(V= Δx/Δt). Unlike speed, velocity is directional, and can be positive or negative depending on whether the displacement is positive or negative. Average velocity occurs over a time interval and is the overall displacement of an object divided by the overall change in time. Example: If I walk 5meters North in 1 minute, turn around and walk 5 meters South in 1 minute, stand perfectly still for 2 minutes, then walk 2 meters North in 1 minute, my average velocity can be determined as (Δx= +5 - 5 + 0 + 2= 2meters)/(Δt= 1 + 1 + 2 + 1= 5minutes)= 0.2 m/min.Instantaneous velocity is the velocity at a very particular point in time, and can be found using a graphical representation. Graphical Velocity:On any given graph, the equation for a straight line is y=mx + b where m= the slope of the line and b= the y-intercept. In a graphical representation of velocity(when the direction and speed are constant), the slope of the line equals the velocity. The equation for this line then becomes Xf = v(t)+ X0 where Xf = final position, v=velocity, t= time,and X0 = starting position.Example: Consider the graph below;For this graph, Xf = 40m, t= 4-1= 3s, and X0= 10m. Therefore, v=(40m - 10m)/3sPosition (x)in metersTime (t) in secondsVelocity= 10m/sIf velocity is not constant, the graphical representation will form a curve instead of a straight line. In this case, to find an object’s instantaneous velocity at a specific point in time you would find the slope of the line tangent to the point in time you are looking at.Example: Consider the graph below; In this graph, the average velocity is represented by the curved line. If we were looking for the instantaneous velocity at t=3s, we would look at the tangent line and figure out the slope of that line using the same formula as the previous graph. Acceleration: defined as a change in velocity over a change in time (a = Δv/Δt). In a graphical representation of acceleration, v=a(t) where acceleration(a) is determined by the slope. Acceleration on a graph typically results in curvature. The tighter or steeper the curve is, the greater the acceleration. Because velocity can be positive or negative, acceleration can also be positive or negative, depending on the direction of the curve. Example; Position (x) in metersTime (t) in secondsPositive Acceleration CurveNegative