Peer Led Team Learning Motion Chapter 1 Pages 14 31 Review Questions 3 8 10 22 24 26 28 Textbook website access www physicsplace com Login GreatWOUstudent Password Aplus2009 Notice which letters are capital and small No spaces in either code I will write this inside the cover of the library copy Or you can set up your own login and pass word with your own access code Course Schedule Note do review question in prologue for Jan 6 not the ones in Ch 1 PLTL ES105x CRN 21433 Monday or Wednesday 5 45 7 45 Library room HL 101 Teresa Trump Study of Motion Galileo Aristotle 4th century BC Student of Plato Tutor of Alexander Used logic to describe natural world collected classified Motion ceased when objects in their proper place Thought speed of falling objects depended on their weight Ignored friction air resistance Influential for 2000 years Aristotle marble portrait bust Roman copy 2nd century BC of a Greek original c 325 BC in the Museo Nazionale Romano Rome Studied Copernicus work of 1543 Use experiment to test logical ideas Discovered speed not dependent on weight only on amount of time for falling http airandspace si edu etp discovery disc galileo html Study of Motion Defined inertia keep moving in same direction and speed without outside influences resistance to change of motion Speed not dependent on weight only on amount of time for falling Noted that gravity increased speed of falling objects decrease speed of rising objects Galileo s inclined planes Balls roll down faster and faster Roll up slower and slower Weight not a factor Galileo s investigation of motion Used inclined planes to slow the descent of objects because he didn t have a precise timer 1 Galileo s inclined planes Rises to same height as it is released Height not dependent on incline Mass Measure of inertia How much matter is there Corresponds to weight the influence of the acceleration of gravity on the mass They are proportional Inertia vs weight Weight is the force due to gravity pulling iron ball down Inertia is resistance to change of movement ball is not moving Pull slowly you increase force and break string that is holding the ball up Rapid jerk will break string below ball because it has large mass that is not moving has inertia Objects not moving Force Mass Measured in kilograms Influence of gravity gives weight Pounds Newtons lb N On Earth 1 kg 9 8 N Not a measure of volume Applied forces Weight is a force due to gravity Force is VECTOR QUANTITY Vectors have magnitude and direction Multiple vectors add up Objects not moving Force of weight is equal to force of string holding it up The sum of the forces is zero There is mechanical equilibrium In equilibrium Support Force Weight acts downward Atoms push back upward Forces equal in equilibrium 2 Dynamic Equilibrium Can be moving At a constant speed in a straight line Net forces are zero Speed speed Miles per hour mph Means miles per hour Don t use this abbreviation of the words Use mi h 80km h Speed of cheetah 100m 4s Force that acts to resist motion Always in opposite direction to applied force When you are pushing something and it moves at a constant speed the frictional force is the same as the pushing force Common units of speed distance time 320km 4h Friction 25m s Kilometers per hour Meters per second km h m s Distance equation Rate time distance Keep units with numbers so you know you have set up the problems correctly Study of Motion Speed how fast Velocity how fast and what direction Acceleration how fast it is changing how fast How to Convert mi h to m s 25mi 1h 60 sec 1610m h 60 min min mi 25mi 1h 1 min 1610m 11 2m h 60 min 60 sec mi s Example of rt d calculation 80km 4h 320km h Notice that hours cancels because it is above and below the fraction bar 3 Car traveling Speed and Velocity 60 km h for 4 h Acceleration 60km 4h 240km h Change in velocity Time interval CHANGE of speed over time not the RATE of speed 60 km h for 10 h 60km 10h h Acceleration RATE OF CHANGE 600km Delta Examples of acceleration Acceleration of gravity is the fourth letter in the Greek alphabet Used in equations to represent change v change in velocity 45mi 20mi Driving on Monmouth Avenue at 20 mi h h h Increase to 45 mi h in 25mi 25 seconds change h in speed is 25mi h Divide change of a 1mi h s speed by time 25s 9 81 m s2 at sea level Round off to 10 m s2 for ease of calculation unless you are trying to launch a rocket to space etc Find final velocity find initial velocity and subtract t change in time or time interval from beginning to end Units of time appear twice in denominator 25mi 11 2m s h 11 2m s 0 44 m 25s s2 4
View Full Document
Unlocking...