1. Physics Section 2.2 Apply acceleration to motion
Acceleration is the rate of change of velocity with respect to time.
Acceleration has both magnitude and direction.
Average acceleration = change in velocity
change in time
aav = Δv = vf – vi
Δt tf - ti
aav = average acceleration (m/s2)
vf = final velocity (m/s)
vi = initial velocity (m/s)
tf = final time (s)
ti = initial time (s)
Motion of a car with an acceleration of -5 m/s2
Time (s) velocity (m/s) acceleration (m/s2)

2. Practice problems
1. As a shuttle bus comes to a sudden stop to avoid hitting a dog, it accelerates uniformly at -4.1 m/s2 as it slows from 9.0 m/s to 0.0 m/s. Find the time interval of the acceleration.
2. Brooke’s treadmill runs with a velocity of -1.2 m/s and speeds up at regular intervals during a half-hour workout. After 25 minutes, the treadmill has a velocity of -6.5 m/s. What is the average acceleration during this period?

3. Acceleration is the slope of the velocity-time graph
Constant acceleration
Variable acceleration

4. Constant acceleration formulas for straight line motion
Object with initial velocity
Object starting from rest
∆x = ½ (vi + vf) ∆t
vf = vi + a(∆t)
∆x = vi (∆t) + ½ a(∆t)2
(vf)2 = (vi)2 + 2a(∆x)
∆x = displacement(m)
vi = initial velocity (m/s)
vf = final velocity (m/s)
a = acceleration (m/s2)
∆t = time (s)
∆x = ½ vf (∆t)
vf = a(∆t)
∆x = ½ a(∆t)2
(vf)2 = 2a(∆x)

5. problems
Cole’s car has an initial speed of 6.5 m/s and accelerates at a uniform rate of .92 m/s2 for 3.6 s. Find the final speed and the displacement of his car during this time.
Stutterheim’s scooter is traveling at 15.0 m/s when he applies the brakes causing it to decelerate at m/s2 . How long does it take for the scooter to reach a speed of 10.0 m/s? How far has the scooter traveled during the braking period?

6. Problems
A car traveling initially at 7.0 m/s accelerates at a rate of .80 m/s2 for a distance of 245 m. What is its velocity at the end of the acceleration?
An aircraft has a liftoff speed of 33 m/s. What is the minimum acceleration required if the aircraft has a runway of 240 m?

7. assignment
Page 59
Problems 1,2,3,5,6