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A change in position relative to some reference point during a period of time. Motion

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Rate at which an object moves Speed = distance/time Units: m/sec, km/hr, mi/hr. Speed d s t

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Instantaneous Speed – speed at a given instant. Average Speed = distance/ time. Describes speed of motion when speed is changing. Constant Speed – speed that doesnt change. Types of Speed

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Speed Problems What is the speed of a cyclist who travels 50 meters in 25 seconds? S = d/t You are in a car traveling an average speed of 60 km/hr. The total trip is 240 km. How long does the trip take? t = d/s 50 m/25 s2 m/s 240 km/60 km/hr 4 hrs.

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Distance -Time Graphs Distance (m) Time (sec) Distance (m)

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Speed in a given direction. Uses: Navigation (airplanes, ships), weather, etc. Vector quantity – represented graphically by arrows ( ). –Length = magnitude –Arrowhead = Velocity direction

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If you row a boat upstream at 10 km/hr and the river has a downstream velocity of 5 km/hr, you are actually moving at what velocity? Velocity Problem 10 km/hr upstream 5 km/hr downstream 5 km/hr upstream =

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Rate of change in velocity. Really a description of how fast you can go in a certain amount of time. Good acceleration is being quick to change. Acceleration

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Examples: speeding up (+ acc.), slowing down (- acc.), or changing direction. Acc. = final velocity – original velocity/time. Units: m/sec/sec Represented by a Velocity – Time Graph Acceleration

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Velocity vs. Time Graphs Time (sec) Velocity (m/s) Time (sec) Velocity (m/s) Time (sec) Velocity (m/s) Time (sec) Velocity (m/s)

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A car increases its speed from 60 km/hr to 80 km/hr in 4 seconds. What is the cars acceleration? Acceleration Problem 80 km/hr – 60 km/hr 4 sec. 1 st second – 65 km/hr 2 nd second – 70 km/hr 3 rd second – 75 km/hr 4 th second – 80 km/hr 5 km/hr/sec. Acc = Δ velocity time

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Rates of Motion Table RatesDefinitionEquationUnitGraph Speed Velocity Acceleration

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Acceleration on an object caused by gravity. Gravitational Acceleration

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Falling Objects Free fall – considers only gravity & neglects air resistance. All falling objects accelerate at the same rate, regardless of their masses m/sec/sec or 32 ft./sec/sec. on earth. - velocity increases 9.8 m/s each second. - distance fallen – increases mathematically

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Instantaneous speed v f = v i + at Distance fallen d = v i t + ½at 2 Average speed v = v i + v f Uniform Motion Equations 2

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Objects Thrown Straight Up

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Graphing Free Fall Distance (m) Time (sec) velocity (m) Time (sec)

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Air resistance noticeably alters the motion of things like falling feathers or pieces of paper. Less noticeably on more compact objects. e.g. stones, balls Air Resistance on Falling Objects

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