Wednesday, September 16, 2009

wednesday 9-14-09 daily blog

1 comment:

  1. In class today Mr. Lane showed us a powerpoint on old and new terms. The things covered were distance, displacement, speed, the equation triangle, velocity, and acceleration.


    Stuff to know


    1. displacement only looks from beginning to end
    (Avg- average)
    Speed/velocity- avg V=d
    ----
    t
    avg V= x (horizontal)
    ----
    t
    avg V=y (vertical)
    ---
    t
    2. X and Y are still distances but they tell us which direction.
    3. Velocity can be negative or positive which is just saying that positive is the first direction, then the opposite of that direction is negative.

    4. Average velocity: avg v= (V0+ Vf)
    ---------
    2
    (just like in math, the average velocity is all the velocities added together then divided by how many there are.
    5. Acceleration: can only have acceleration if velocity changes.
    A= delta V
    ------
    t
    D= 1/2 t+ 1/2 a t(squared)
    Delta: looks like a triangle, means "the change in"
    Vf-Vi
    -----
    t

    Vf= Vo+ at


    Application:
    First equation:

    A car is moving at 10m/s and 4 seconds later it is moving 30 m/s. What is its average acceleration in this 4 second time period?

    1. Identify the concepts.
    acceleration (a)
    Time (t)

    2. identify units.
    10 m/s - Speed
    4 seconds- Time 2 speeds! so one is initial and one is final
    30 m/s- Speed

    3. Identify all symbols.
    a
    t
    V0
    VF

    4. Identify the correct tool/equation
    A= Vf-Vo
    ------
    t
    5. Plug and chug

    (figure out what to plug in and where

    A= (30m/s-10m/s)
    --------------
    4s
    A=5 m/s




    Second equation:
    A car traveled 100 meters in 5 seconds. Its final velocity was measured to be 25 m/s. What was its initial velocity in the 5 second time interval?

    1. Identify the concepts.
    Velocity (Vf)
    Time (t)
    Velocity (Vi)

    2. Identify the units
    100 meters- distance
    5 seconds-Time
    25 m/s- Velocity final

    3. Identify all symbols.
    V0
    Vf
    t
    d

    4. Identify the correct tool/equation
    D (Vf+V0)
    --= -------
    t 2


    5. Plug in

    100m (25m/s + ????)
    -----= ------------
    5s 2

    V0= 15 m/s

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