PHY 102 1nd Edition Lecture 7 Outline of Last Lecture I Blue Book Problems Outline of Current Lecture I II III Motion Uniformly Accelerated Motion UAM Blue Book 3 1 Current Lecture I Motion Rectilinear a The simplest kind of motion takes place on a straight line b Three quantities that describe this motion i Distance displacement ii Speed velocity 1 meters second m s iii Acceleration Quantities in bold can be positive or negative c The simplest kind of rectilinear motion is uniform motion in which velocity does not change i x vt ii speed distance time 1 v x t iii 1 mile per hour 1 mile 1 hr 1610 m 3600 s 0 4472 m s 1 Example IL speed limit 70 mph 70 0 4472 31 3 m s iv The best way to learn rectilinear motion is graphs 1 Plot velocity versus time on a graph 2 Distance velocity and acceleration can be easily identified on such a graph 3 Uniform motion velocity as a function of time 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 II a How do you represent the distance on such a graph How do you find the distance covered in 15s 8 15 geometry height width AREA 4 Area as distance is not limited to uniform motion It can be used in general a Of course you can t multiply velocity by time because velocity keeps changing in a general motion b But if your time interval is very short velocity is almost constant during that time and you can use the distance as area idea i Break up the large time interval into a lot of very short small intervals ii Calculate the distance for each short interval and add them all together 5 So far we have learned how to find the velocity and distance for a moving object a For velocity read off the plot value For distance measure the area under the v t curve 6 What about acceleration a acceleration change in velocity time a v t Unit meters second2 m ss b Instantaneous acceleration a v t t is very small c Remember v can be either positive or negative i a 0 means velocity increases speeding up ii a 0 means velocity decreases slowing down d Graphically tangent line is the time Uniformly Accelerated Motion UAM III a Acceleration does not change b Slope does not change straight line i y mx b c v at vo d distance area of trapezoid area of rectangle area of triangle i area of rectangle tvo vot ii area of triangle t v vo at2 e x vot at2 i a can be either positive or negative Blue Book 3 1