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Published byLoren Dott Modified about 1 year ago

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Motion

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Motion: The change in position of an object as compared with a reference point Reference point: System of objects that are not moving (stationary) in respect to one another

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Length of path between 2 points May not be straight line (shortest path) Units: meters (m), km, miles, cm, etc. Ex: Roads/streets we drive

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The direction and length in a straight line from start to end ALWAYS includes direction from start point Ex: walk 5 blocks north from McDonald’s Ex: roller coaster ride displacement = 0

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How fast in a given amount of time 1. Distance traveled by object 2. Time to travel that distance Units: ◦ m/s ◦ mi/hr or mph ◦ km/hr

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Average Speed - Calculated speed for trip Ex) Ran marathon at 6 mi/hr Instantaneous Speed - speed at exact moment Ex) speedometer reading = 55 mi/hr Object going an equal distance in equal amounts of time = Constant speed (not speeding up or slowing down)

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Doesn't tell the direction 45 mph 4 m/s

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Expressed in m/s Speed = Distance/Time Or S = d/t Ex: A car traveling at a constant speed and it goes and distance of 645 m in 25 s. What is the car’s speed? S = d/t S = 645m/25s S = 25.8 m/s

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Graphs show speed/velocity Time (independent variable) -> x-axis Distance (dependent variable) -> y-axis

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Slope of line = speed or velocity Straight line = constant speed (cruise control) Steeper slope = faster speed

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Horizontal (flat) line = object not moving Exs: stopped at red light, parked, at store

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Negative slope = went backwards (neg. displacement) Ex: went to store, shopped, and back home

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Measurements: Speed: m/s, km/h, or m/h Direction: N (NE, NW), S (SE, SW), East, and West Describes both speed and direction of motion Must give how “fast” and direction the object is going Ex: 45 km going South

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Can be described as changes in speed, direction, or changes in both Small value = increasing gradually Larger value = speeding up more rapidly The slope of a speed-time graph is acceleration

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Positive Acceleration – velocity increases or speeds up (gives a positive slope ) Negative Acceleration – velocity decreases or slows down (gives a negative slope ) Horizontal line – on a velocity-time graph; stays constant, velocity does not change (--- --)

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Any change in how fast or change in direction Speed up Slow down Turn a corner Go around a curve

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Acceleration = change in velocity/time a = (final velocity – initial velocity)/time Measured in meters/second/second a = vf - vi/t

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Calculating positive acceleration = pos. # (speeding up) Ex: a = (80m/s – 0m/s)/20s = 4m/s Calculating negative acceleration = neg. # (slowing down) Ex: a = (0m/s – 3m/s)/2s = 1.5 m/s

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Causes velocity change Unit = Newton (N) Net Force - combo of all forces acting on object Net force = 0 Either stopped or constant speed

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2 Types of forces: 1. Balanced Forces - net force = 0 Forces cancel out Ex) Fair tug of war 2. Unbalanced Forces - net force not = 0 One force is stronger Car vs Train

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Physicist who described relationship between force & motion 3 Laws: Newton’s Laws of Motion

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AKA – Law of Inertia “An object at rest stays at rest, and an object in motion stays in motion, unless acted upon by an unbalanced force.” Inertia = tendency of object to stay at rest Exs: car crashes, magician table cloth trick

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1 st Law

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