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MOTION Unit 9, Chapter 11

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I. Describing Motion Frame of reference: A. Frame of reference: what motion is compared against. relative B. Motion is relative or dependant on the frame of reference. (Einstein) The car moves left in reference to the Earth The most common frame of Reference is the Earth.

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Now lets get tricky! The corvette will be going forward and backward! - forward in relation to the Earth - backward in relation to the Indy car

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Distance and displacement II. Measuring Motion Distance: A. Distance: the length of a path between two points. Direction- B. Direction- relative to a F.O.R. Time C. Time needed to complete the motion. The above items are known as: They have magnitude only.

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Displacement Displacement:distanceand D. Displacement: The distance and direction direction from the starting point, to the ending point in a straight line (As the crow flies) Go to map.

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vectors III. Vectors A. Are arrows that show magnitude and direction. B. Displacement can be displayed as a vector. 4 miles 2 miles C. Vectors can be combined. 4 miles2 miles + = + 4 miles = Like this

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Pythagorean Or this

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speed IV. Speed A. What are some examples of speed? B. Speed is measured by the distance traveled in a certain amount of time. C. Calculated as: D. Units: mi/hr, m/s, km/hr (a scalar) Speed = Distance = d Time t

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Instantaneous speed V. Instantaneous Speed A. Your speed the moment you look down at the speedometer. B. Calculated by: speed ( V ) = distance (d) time (t) C. Example:

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Instantaneous speed VI. Average Speed A. Calculated by: avg. speed = total distance total time B. Symbol Equation:

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Instantaneous speed C. Example: What is the avg. speed if a car travels 2 miles in 4 minutes, stops for 1 minute and travels 3 miles in 3 minutes?

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velocity VII. Velocity Velocity is speed with an indicated direction. Examples: 65 mi/hr North, 12 m/s Up Indicated by the use of a Vector 10 meters / second The arrow = direction Magnitude (length) tells how much 10 meters/second

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VIII. Acceleration A. Acceleration is any change in velocity. B. Acceleration is any change in speed or direction. C. We calculate acceleration with the following equation: Acceleration = Final Velocity Initial Velocity Change in Time

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Acceleration example D. Example: A car traveling at 30 mi/hr increases speed to 60 mi/hr in 6 sec. What is the cars acceleration? a = = vv tt v f - v i t v f = 60 mi/hr v i = 30 mi/hr t = 6 sec a = = 60 mi/hr 30 mi/hr 6 sec 30 mi/hr 6 sec 5 mi/hr/s = 5 mi/hr/s What does this answer mean? For each second that passes the car is traveling 5 mi/hr faster than before.

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Acceleration continued E. A positive acceleration means speeding up. F. A negative acceleration means slowing down. G. Acceleration can be expressed as a vector since it includes direction.