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Physics 11 Advanced Mr. Jean February 6 th, 2012

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The plan: Introduction to kinematics Commonly used variables Scalars & Vectors Speed Average speed Velocity Quantum Futures

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Kinematics: That branch of physics which deals with the motion of objects without reference to the forces which act on the system

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x i = starting location “initial position” (m) x f = ending location “final position” (m) v i = final velocity (m/s) v f = initial velocity (m/s) a = acceleration (m/s 2 ) θ = angle in degrees t = time (s) Important Variables:

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Vectors & Scalars: Scalars are quantities we measure in everyday life. (Mass, time, energy etc…) In physics we normally describe motion in terms of vector. We have a quantity, but also a direction the quantity is travelling in. Distance and speed are scalars; however positive displacement, velocity, and acceleration are vectors.

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Scalars vs. Vectors: Scalar QuantitiesVector Quantities Distance – 15kmDisplacement – 15km [N45 0 E] Speed – 30 m/sVelocity – 30m/s [S]

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The basics of measuring motion: Speed is measured in meters per second (m/s) x i = starting location (meters) x f = final location (meters) t i = starting time (seconds) t f = end time (seconds) Speed: Speed = x f – x i t f - t i

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The basics of measuring motion: Average Speed: Average Speed = Total distance (m) Total time (s) –Always measured in meters per second (m/s) for physics class.

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The basics of measuring motion: Velocity is a vector, thus you must give it a direction. The international SI unit for velocity is meters per second (m/s). x i = starting location (meters) x f = final location (meters) t i = starting time (seconds) t f = end time (seconds) Velocity: v = x f – x i t f - t i

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The basics of measuring motion: a = acceleration (m/s 2 ) v i = initial velocity (m/s) v f = final velocity (m/s) t i = Starting time (s) t f = End time (s) Acceleration: Acceleration [Direction] = v f – v i t f - t i

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Constant acceleration equation #1: v f = v i + at v f = Final velocity in m/s v i = Initial velocity in m/s a = acceleration in m/s 2 t = time in seconds

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Constant acceleration equation #1: Other Notation: Means the same thing, just different subscripts. v = v o + at v = Final velocity in m/s v o = Initial velocity in m/s a = acceleration in m/s 2 t = time in seconds

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Example #1 A slip and slide uses gravity to accelerate people down a hill. On Ron’s awesome slip and slide people accelerate from 0m/s to 20m/s in 4 seconds. Find the acceleration in this situation.

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Example #2: Hailey’s ball is rolling away from her at 2m/s. It start to accelerate down a steep hill at the rate of 4m/s 2 and continues to do so for 4 seconds. What is the balls final velocity?

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x - x o = v o t + ½ (a) (t 2 ) x = Final distance (m) x o = Initial distance (m) v o = Initial velocity (m/s) t = time (s) a = acceleration (m/s 2 ) Constant acceleration equation #2:

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x f - x i = v i t + ½ (a) (t 2 ) x f = Final distance (m) x i = Initial distance (m) v i = Initial velocity (m/s) t = time (s) a = acceleration (m/s 2 ) Constant acceleration equation #2:

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Examples for this tomorrow:

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Quantum Futures: Finish watching Quantum Futures. Once this is complete the remaining few minutes is in class time to complete worksheet #1. Remember there is a homework check tomorrow!

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