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Reading assignment before next class : To finish the entire Chapter 2 (see Syllabus) Help session Today: Math and HW 1a1b
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Accelerations is vectors! They have directions.
Which cars are speeding up and which ones are slowing down?
When acceleration & velocity are both positive or both negative, speed increases. When acceleration and velocity have opposite directions, speed decreases.
Does positive acceleration mean speeding up? Does negative acceleration mean slowing down?
When a>0, v<0, acceleration is opposite to velocity. (velocity change is opposite to velocity), Speed decreases (decelerating).
When a<0, v<0, speed increases, moves faster and faster toward negative direction
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Position and velocity change all the time, but the rate of velocity change stay constant. a=aav= constant
a= slope of the v vs. t plot.
Constant Acceleration Motion
Initial: x0 v0 a
Final: (at time t) x = xf v = vf a=a
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If upward is chosen to be the positive x direction, v= v0 – 9.81 t Dx=v0t – ½ (9.81 t2)
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