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# 09

## on Oct 27, 2009

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## 09Presentation Transcript

• Warm-up, 09.08.2009
Name one important physicist and any of their achievements. Why is physics something we should all be aware of?
Nombre un físico importante y a cualquiera de sus logros. ¿Por qué está la física algo que nosotros deben toda ser consciente de?
Nommez un physicien important et n&apos;importe lequel de leurs accomplissements. Pourquoi la physique quelque chose que nous est-elle devrait tout se rendre compte de ?
• Motion Ch. 3 S 2 - Acceleration
• Acceleration – The change in velocity divided by the time it took for that change to occur
Review: What is Velocity?
Basically, this means the change in speeds divided by the time…..-OR –
Average acceleration =
(Vf-Vi)/(Time)
Ex: Lamborghini’s are known for their speed and record setting acceleration. These lamborghini’s accel to 60 miles per hour (100km/h) in 3.4 seconds!!
Can you calculate their average acceleration in METERS/second?
• Incredible Hulk Vs. A LAMBO!
The Incredible Hulk accelerates to 40 miles per hour ( 62 km/h) in 2 seconds.
What is its average acceleration?
Compare this with the lamborghini’s acceleration and tell me who has the faster acceleration.
• Calculating Positive and Negative Acceleration
If the slope is Negative, then the acceleration is decreasing. This means the object is slowing down.
If the slope is positive, then the acceleration is positive. This means the object is speeding up.
If the slope is zero, then the speed is not changing. The object is going at a constant speed
Distance (Meters)
40
20
10
40
20
30
Time (minutes)
• Calculations =( Sorry for all the math…….
Ex: Calculating NEGATIVE acceleration (A.K.A. DEcelleration:
Mr.B is skateboarding down a ramp and she is cruising at a cool 14 miles per hour. Then, when he goes up the ramp, he falls over and comes to a stop in 2 seconds. What is his Deceleration?
• Chapter 3 Section 3
Forces!!!
• What are forces?
(I am not talking about shoes =)
A force is a push or pull that one object exerts on another.
Net Force – The TOTAL amount of force on an object.
Balanced Vs. Unbalanced Forces
Balanced - when the net force is equal to zero
Unbalanced – when the net force is NOT equal to zero.
See this stuff is EEEAASSSYYYY!
• To Recap:
Acceleration: (final velocity in meters per second) - (initial velocity in meters per second) / (final time - initial time)
(Vf-Vi)/(Time)
An accelerating object is a POSITIVE number
Deceleration: The same equation as acceleration, but the result will be a NEGATIVE number.
Force: a push or pull.
Two or more forces acting on an object create a Net Force.
Balanced forces: net force is = 0
Unbalanced force: net force is NOT = 0
• To recap:
Friction: the force that slows down, stops, or prevents two objects in contact from sliding forever.
Static friction: When friction &gt; the force trying to move it.
Sliding friction: the force of friction moving in the opposite direction of the object moving.
Air Resistance: Friction caused by air on falling objects.