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# Acceleration

## on Sep 22, 2011

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## AccelerationPresentation Transcript

• 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.
• 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 brakes to
avoid hitting a deer. The car comes to a safe stop
6 seconds after applying the brakes. 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
• 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
• Balloon Racers
What will happen if I let go of the blown up balloon?
Why did that happen?
How can we measure the speed, distance or acceleration of the balloon?
A track?
Attach the balloon to something?