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

3. Acceleration=Acceleration= final velocity- starting velocityfinal velocity- starting velocity
timetime
Change in velocity = finalChange in velocity = final
–– startingstarting
velocity velocityvelocity velocity
Acceleration=Acceleration= change in velocitychange in velocity
timetime

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

5. PositivePositive
accelerationacceleration
NegativeNegative
accelerationacceleration

6. Acceleration =
Velocity(final) - Velocity(original)
time
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?
=
0 mph - 60 mph
6 seconds
=
- 60 mph
6 seconds
= - 10 miles per hour per second

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

8. Free fallFree fall
 The constant acceleration of anThe constant acceleration of an
object moving only under theobject moving only under the
force of gravity is "g".force of gravity is "g".
 The acceleration caused byThe acceleration caused by
gravity is 10 m/sgravity is 10 m/s22
 If there was no air, all objectsIf there was no air, all objects
would fall at the same speedwould fall at the same speed
 Doesn’t depend on massDoesn’t depend on mass
 After 1 second falling at 10 m/sAfter 1 second falling at 10 m/s
 After 2 seconds 20 m/sAfter 2 seconds 20 m/s
 3 seconds 30 m/s3 seconds 30 m/s

9. GalileoGalileo
 1600’s1600’s
 Studied how things fellStudied how things fell
 Didn’t have a good clockDidn’t have a good clock
 Rolled balls down anRolled balls down an
inclined planeinclined plane
 Found that the speedFound that the speed
increased as it rolledincreased as it rolled
down the rampdown the ramp

10. GalileoGalileo
t = 0
t = 1 second
t = 2 seconds
t = 3 seconds
Acceleration=Acceleration= change in velocitychange in velocity
timetime

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

12. vv22
finalfinal = 2gd= 2gdyy
 A final velocity can be calculatedA final velocity can be calculated
over a vertical displacement “dover a vertical displacement “dyy""
during free fall using the equation:during free fall using the equation:

13. ddyy = 1/2 gt= 1/2 gt22
 The vertical displacement “dThe vertical displacement “dyy" that" that
occurs during a specific time of free falloccurs during a specific time of free fall
can be determined using the equation:can be determined using the equation:
 Or a time interval can also beOr a time interval can also be
determined over a specified distancedetermined over a specified distance
of freefall using the equation:of freefall using the equation:
tt22
= 2d= 2dyy /g/g

14. FallingFalling
 Air resistance willAir resistance will
increase as it falls fasterincrease as it falls faster
 An upward force on theAn upward force on the
objectobject
 Eventually gravity willEventually gravity will
balance with airbalance with air
resistanceresistance
 Reaches terminal velocityReaches terminal velocity
- highest speed reached- highest speed reached
by a falling object.by a falling object.

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