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Notes September , 2013
How do you know when something is in motion??
Motion: The state in which one object‛s distance from another is changing based on a reference point. An object is only in motion when its distance is changing.
Reference Point: A place or object used for comparison to determine if something is in motion.
Distance: the total length between two points traveled.
Vector: a physical quantity that is specified by a size and direction. Ex.
Displacement: a vector that refers to "how far out of place an object is"; how far an object is from its starting position.
Distance vs. Displacement
Ex.Walk 1 mile to the movies and continue to walk 1/2 mile for ice cream in the same direction (east).
Distance = ___________Displacement = ___________
After ice cream you walk 1 mile to your friends house (west).
Distance = ___________Dispacement = ___________
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Reference PointsExample...How fast are you moving sitting at your desk relative to the floor?
Relative to the Sun?
Sitting in your car at a stop light... next to a big vehicle...
Being on a cruise ship...
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Speed - a measure of an object's distance covered over an amount of time.
**FORMULA**
**UNITS**
Speed = Distance ÷ Time
m/s <-- Used most often (Whatever the distance unit is / what the time unit is)
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Speed
Distance
Time
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Acceleration: The rate at which speed/velocity changes.
• Increasing Speed- (Positive Acceleration)A car moving from a stopped position
• Decreasing Speed (Negative Acceleration OR Deceleration) A ball decelerates when rolling to a stop, a jetlanding on a runway
• Changing Direction A car moving around a curve at constant speed (still accelerating because the car is changing direction)
Velocity: The speed of an object and the direction of its motion. (Velocity is a vector)Ex. The hurricane is moving at a speed of 10 km/h East.
Notes October 2013
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Acceleration FormulaAcceleration = Final Speed - Beginning Speed
Time
Units = m/s2
Shorter Version -->
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While drag racing out of our school parking lot, I time myself at a speed of 40 m/s 7 seconds after starting.
What was my acceleration?