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Homework Help: Find Velocity and acceleration

  1. Sep 18, 2010 #1
    A particle starts from the origin at t = 0 and moves along the positive x axis. A graph of the velocity of the particle as a function of the time is shown in Fig. 2-43;

    144302b2-a5d9-4a80-a60b-3143ed308917.png

    the v-axis scale is set by vs = 7.00 m/s. (a) What is the coordinate of the particle at t = 5.0 s? (b) What is the velocity of the particle at t = 5.0 s? (c) What is the acceleration of the particle at t = 5.0 s? (d) What is the average velocity of the particle between t = 1.0 s and t = 5.0 s? (e) What is the average acceleration of the particle between t = 1.0 s and t = 5.0 s?

    2. Relevant equations
    Vf= Vi+at
    Vavg = (Vf+Vi)/2
    a avg= change in v/change in time


    3. The attempt at a solution

    I think all my answers are wrong!
    a) (2,5) --> Looking at the graph

    b) t =5s, v=2 m/s

    c) Vf= Vi+at
    (4-2)/1 = a
    a = 2 m/s

    d) Vavg = (Vf+Vi)/2
    (2=2)/2
    = 2 m/s

    e) a avg= change in v/change in time
    =0 m/s
     
  2. jcsd
  3. Sep 18, 2010 #2
    you cannot calculate the coordinate by just looking at the graph. You have to use x=at^2/2
    for b.) its just v_s/2 from the graph

    c, how much the velocity decrease from t=4 to t=5? i.e. in one second?

    d.) the formula is right but u read it wrong from the graph.

    e,) correct.
     
  4. Sep 18, 2010 #3
    for A, x=at^2/2
    how do I find a??

    Thanks though :D
     
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