Presentation Transcript
Acceleration :Acceleration Change in velocity
Can be change in speed or direction
Acceleration = ∆V/ ∆T
∆V
a t
Acceleration problem :Acceleration problem A roller coaster’s velocity at the top of a hill is 10m/s. Two seconds later it reaches the bottom of the hill with a velocity of 26m/s. What is the acceleration of the roller coaster?
Answer :Answer Acceleration = ∆V/ ∆T
a = 26m/s – 10m/s
2 s
a = 16m/s
2s
a = 8m/s/s or 8m/s2
More acceleration problems :More acceleration problems 1. A car accelerates at a rate of 20mi/hr/s. How long does it take to reach a speed of 80 mi/hr?
2. A car travels at 60 miles per hour around a curve. Is the car accelerating?
3. A car travels in a straight line at 60mi/hr. Is the car accelerating?
Answers: :Answers: 1. ∆V 80mi/hr
a t 20mi/hr/s t
4sec = t
2. yes! Because it’s changing direction!
3. no! It’s not changing speed or direction!
Deceleration :Deceleration Negative acceleration
Example: A car slows from 60mi/hr to 20mi/hr in 4 seconds. What is its acceleration?
Answer: :Answer: Acceleration = ∆V/ ∆T
Acceleration = Vf – Vi
t
a = 20mi/hr – 60mi/hr
4 s
a = -40mi/hr
4s
a = -10mi/hr/s
Review: Distance-time graph of acceleration :Review: Distance-time graph of acceleration
Distance-time graph of deceleration :Distance-time graph of deceleration
Review:Speed-time graph of acceleration :Review:Speed-time graph of acceleration
Review: Speed-time graph of deceleration :Review: Speed-time graph of deceleration
Review: Distance-time graph of constant speed :Review: Distance-time graph of constant speed