1. Aim: How do we explain accelerated motion?

2. Uniform and Non-Uniform Motion
Uniform motion- object moves at constant velocity
Non-uniform motion-object does not move at constant velocity
Which object is moving uniformly?
A body thrown off an airplane.
A train moving in a straight line at constant speed.
A person on a merry go round.

3. Uniform vs. Non-uniform Motion
1) Describe the motion of this car.
2) What is the car’s average velocity?
3) Is the car always traveling at this velocity?

4. Average Velocity vs. Instantaneous Velocity
Instantaneous velocity- the velocity at any given instant of time Average velocity- the average of all instantaneous velocities (v = d/t)

5. Acceleration
When an object’s velocity changes, we say it undergoes acceleration. a= ∆v/∆t ∆v = vf – vi

6. Example
Lady Gaga accelerates from rest to a velocity of 10 m/s in 5s. Calculate her acceleration.
a = ∆v/∆t

7. Which object accelerates?
Which car(s) are accelerating?
Which car experiences the greatest acceleration?
Is acceleration a vector or scalar quantity?

8. The four cases problem
Calculate the acceleration in each of the following cases:
∆t = 3s for each case
vi = 12 m/s and vf = 24 m/s
vi = 24 m/s and vf = 12 m/s
vi = -12 m/s and vf = -24 m/s
vi= -24 m/s and vf = -12 m/s

9. Problem
A roller coaster car rapidly picks up speed as it rolls down a slope. As it starts down the slope, its speed is 4 m/s. But 3 seconds later, at the bottom of the slope, its speed is 22 m/s. What is its average acceleration?