1. Acceleration

2. Change in Velocity
Each time you take a step you are changing the velocity of your body.
You are probably most familiar with the velocity changes of a moving bus or car.
The rate at which velocity (speed or direction) changes occur is called acceleration.

3. Change in velocity = final – starting velocity velocity
Acceleration= final velocity- starting velocity
time
Change in velocity = final – starting velocity velocity
Acceleration= change in velocity

4. A car traveling at 60 mph accelerates to
90 mph in 3 seconds. What is the
car’s acceleration?
Velocity(final) - Velocity(original)
Acceleration =
time
90 mph - 60 mph =
3 seconds
30 mph =
3 seconds =
10 mph/second

5. Positive acceleration Negative acceleration

6. A car traveling at 60 mph slams on the breaks to
avoid hitting a deer. The car comes to a safe stop
6 seconds after applying the breaks. What is the
car’s acceleration?
Velocity(final) - Velocity(original)
Acceleration =
time
0 mph - 60 mph =
6 seconds
- 60 mph =
6 seconds =
- 10 miles per hour per second

7. - A constant acceleration produces a straight line or linear slope (rise/run). - The slope of a non-linear velocity-time graph (rise/run) will predict an objects instantaneous acceleration. a = v/t

8. Free fall
The constant acceleration of an object moving only under the force of gravity is "g".
The acceleration caused by gravity is 10 m/s2
If there was no air, all objects would fall at the same speed
Doesn’t depend on mass
After 1 second falling at 10 m/s
After 2 seconds 20 m/s
3 seconds 30 m/s

9. Galileo 1600’s Studied how things fell Didn’t have a good clock
Rolled balls down an inclined plane
Found that the speed increased as it rolled down the ramp

10. Galileo Acceleration= change in velocity time t = 0 t = 1 second
t = 2 seconds
t = 3 seconds

11. Galileo Same things happen when things fall
Didn’t drop things from Tower of Pisa

12. A final velocity can be calculated over a vertical displacement “dy" during free fall using the equation:
v2final = 2gdy

13. The vertical displacement “dy" that occurs during a specific time of free fall can be determined using the equation:
dy = 1/2 gt2
Or a time interval can also be determined over a specified distance of freefall using the equation:
t2 = 2dy /g

14. Falling Air resistance will increase as it falls faster
An upward force on the object
Eventually gravity will balance with air resistance
Reaches terminal velocity - highest speed reached by a falling object.

15. Terminal velocity Force of gravity is constant
air resistance increases as you speed up
until the force is equal
Equal forces, no acceleration
constant velocity terminal velocity