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Principles of Physics motion along a straight line path, motion in one dimension Which way are you headed? How far did you go? How fast are you going? Is your speed changing? Acceleration Rate at which speed changes In other words, speeding up or slowing down Measured in meters per second2 More commonly stated as “the object goes from 0 to 40 m/s in 8 s” Acceleration is calculated 2) a = acceleration (m/s vf vi a vf = final velocity (m/s) t vi = initial velocity (m/s) v f v i at t = time (s) Acceleration is a vector quantity + when speeding up - when slowing down (deceleration) Blue and green cars accelerate, the red car travels with a constant velocity. At rest Starting from rest → vi =0 Initially at rest Comes to rest → vf = 0 1. A particle has a constant acceleration of 2.0 m/s2. Calculate the time required for the particle to accelerate from 8.0 m/s to 28 m/s. Givens: a = 2.0 m/s2 vf = 28 m/s vi = 8.0 m/s t=? vf = vi +at 28 m/s = 8.0 m/s + 2.0 m/s2 (t) 28 m/s - 8.0 m/s = t 2.0 m/s2 10 s = t 2. A car travelling at 32 m/s comes to rest in 30 s. Calculate the acceleration of the car. Givens: a=? vf = 0 m/s vi = 32 m/s t = 30 s vf vi a t 0 32m / s a 30s a 1.07m / s 2 If you do not know the final velocity of an object, but do know the displacement of the object you can calculate the acceleration using: d = vit + ½ at2 d = displacement (m) vi = initial velocity (m/s) t = time (s) a = acceleration (m/s2) 3. A car starting from rest accelerates at 4 m/s2 for 6 s. Calculate the car’s displacement. Givens: vi = 0 m/s a = 4 m/s2 t= 6 s d=? d = vit + ½ at2 d = 0m/s (6s) + ½(4 m/s2 )(6s)2 d = 72 m