Acceleration

1 / 15

# Acceleration - PowerPoint PPT Presentation

Acceleration. 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.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
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.
Acceleration= final velocity- starting velocity

time

Change in velocity = final – starting velocity velocity

Acceleration= change in velocity

time

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

Positive acceleration

Negative acceleration

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

- 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
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
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

t = 0

t = 1 second

t = 2 seconds

t = 3 seconds

Galileo

Acceleration= change in velocity

time

Galileo
• Same things happen when things fall
• Didn’t drop things from Tower of Pisa
v2final = 2gdy
• A final velocity can be calculated over a vertical displacement “dy" during free fall using the equation:
dy = 1/2 gt2
• The vertical displacement “dy" that occurs during a specific time of free fall can be determined using the equation:
• Or a time interval can also be determined over a specified distance of freefall using the equation:

t2 = 2dy /g

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