Midterm Exam 100 90 A 89 80 B 79 70 C 69 60 D 59 or less 5 12 15 13 F High score 70 out of 76 Every score divided by 70 for the percent marked on your exam Average is 72 You can raise your score by doing Part I problems outside class and turning it in at the beginning of class on Tuesday February 21 on separate page turn in both original and new work go see a tutor If you feel I marked an answer wrong in error see me in my office during office hours with documentation of correct answer Study of Motion Aristotle Tutor of Alexander Student of Plato Ignored friction Motion ceased when objects in their proper place Influential for 2000 years Study of Motion Galileo Studied Copernicus work of 1543 Defined inertia keep moving in same direction and speed without outside influences Noted that gravity increased speed of falling objects decrease speed of rising objects Study of Motion Speed how fast Velocity how fast and what direction Acceleration how fast it is changing how fast Speed distance speed time 320km 4h 80km h Distance equation Rate time distance Keep units with numbers so you know you have set up the problems correctly Example of speed calculation 80km 4h 320km h Notice that hours cancels because it is above and below the fraction bar Common units of speed Miles per hour mph mi h Kilometers per hour km h Meters per second m s Speed of cheetah 100m 4s 50m 2s 25m s Car traveling 60 km h for 4 h 60km 4h 240km h 60 km h for 10 h 60km 10h h 600km Acceleration Change in velocity Acceleration Time interval CHANGE of speed over time not the RATE of speed RATE OF CHANGE Examples of acceleration Driving on Monmouth Avenue 20 mi h Increase to 45 mi h in 25 seconds change in speed is Divide by time to change speed 45mi 20mi h h 25mi h 25mi h 1mi h s 25s Rate of change of speed 45mi 20mi h h 25mi h Find how much you change then divide by amount of time over which the change occurs 25mi h 1mi h s 25s Rate of change of speed Car can go from stopped to 90 km h in 10 seconds Be sure to REDUCE to lowest terms 90km h 9km h s 10 s Rate of change of speed Car goes from 60 km h to 65 km h in 2 5 seconds First find amount of change 5km h 2km h s 2 5s Rate of change of speed Bicycle goes from rest to 5 km h in 2 5 seconds 5km h 2km h s 2 5s Acceleration Neglect air resistance for these equations a v t v at acceleration is velocity divided by time velocity acquired is acceleration multiplied by time Acceleration of Gravity 9 8 m s2 Round off to 10 m s2 Acceleration of Gravity Free fall of object Time elapsed Speed increases seconds 10 m s for every second of fall 0 10 m s 10m 1 s s2 2 Speed meters second 0 10 20 3 30 4 40 Problems If a rock is rock is pried loose from a cliff by frost wedging what is its speed 3 5 seconds after it starts falling After 6 seconds After 100 seconds Solution 1 v at 10m v 2 3 5s s a 10m s 2 t 3 5s v 35m s Solution 2 v at 10m v 2 6 s s a 10m s 2 t 6s v 60m s Solution 3 v at 10m v 2 100 s s a 10m s 2 t 100s v 1000m s Acceleration Rate of increase of a rate d t t Increases rate for each increment in time that has passed So there is an increased of distance for each successive time interval Distance g acceleration of gravity a 10m s2 t lower case for time T upper case means Temperature 1 2 1 10m 2 d gt d 2 t 2 s 2 Distance Traveled Time elapsed Speed Distance Total traveled in Distance 1 second traveled 0 0 m s 0 0m 1 10 m s 5m 5m 2 20 m s 15 m 20 m 3 30 m s 25 m 45 m 4 40 m s 35 m 80 m Problem Cat steps off ledge and reaches ground after second How fast was she going when she touched the ground What is the height of the ledge v gt 1 2 d gt 2 Equations How fast How far v gt 1 2 d gt 2 Cat s jump how fast 10m v 2 0 5s s 10m v 2 0 5s 5m s s Cat s jump how far 1 10m 2 d 2 0 5s 2 s 1 10m 2 d 2 0 5s 2 5m 2 s
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