Transcript Acceleration

Acceleration
Movie Galileo
First 1 min 15 sec
http://app.discoveryeducation.com/player
/view/assetGuid/683BF288-CEF9-442D9BD5-2AE2BFC7608C
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
Galileo
t=0
t = 1 second
t = 2 seconds
t = 3 seconds
Acceleration

Acceleration is the rate at which velocity
(speed or direction) changes.

Rate = time

So,

acceleration is change in velocity per time.
3 Types of acceleration
1. Increasing Speed
2. Decreasing speed
3. Changing
Direction
Because of
velocity
Calculating Acceleration
A= change in velocity
time
Change in velocity = final – starting
velocity velocity
A= FV - IV
time
A car traveling at 60 mph accelerates to
90 mph in 3 seconds. What is the
car’s acceleration?
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?
Acceleration
=
Velocity(final) - Velocity(original)
time
=
=
90 mph - 60 mph
3 seconds
30 mph
3 seconds
= 10 mph/second
A car traveling at 60 mph accelerates to
90 mph in 3 seconds. What is the
car’s acceleration?
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?
Acceleration =
Velocity(final) - Velocity(original)
time
=
=
0 mph - 60 mph
6 seconds
- 60 mph
6 seconds
= - 10 miles per hour per second
A car at rest can go 90 km/h in 9
seconds. What is the acceleration?
A person was running down a ramp.
They started going 4 m/s down and
then ended up going 22 m/s at the
bottom. What was the persons
acceleration down the ramp.
???
????????
Positive
acceleration
Negative
acceleration
- A constant acceleration
produces a straight line or
linear slope (rise/run).
- The slope of a nonlinear velocity-time graph
(rise/run) will predict an
objects instantaneous
acceleration.
a = v/t
Galileo
Back
to Galileo
When things fall they get faster and
faster.
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
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.

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