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Homework Help: A baseball is thrown

  1. Sep 25, 2006 #1
    a baseball thrown from rest, leaves a pitcher's hand at v1 m/s. If the average force exerted by the pitcher is doubled, all else remained the same, with what speed will the ball leave the pitcher's hand given v1.

    just looking for some direction, I haven't done problems like this in a long while and was trying to offer a friend some help. I was thinking that I needed to use kinematics to solve this problem but I was having problems relating constant acceleration to velocity without incorporating an equation using time.

    v=v0+at=> a=v-v0/t

    f=ma===> f=m(v-v0/t)...

    any help would be appreciated.
  2. jcsd
  3. Sep 25, 2006 #2
    You cannot use the kinematical relations because nothing has been specified about the accelaration, and in particular, whether it is a constant.

    The average force exerted during a time interval [tex]\Delta t[/tex] is, [tex]\left<\vec{F}\right> = \frac{\Delta\vec{p}}{\Delta t}[/tex], where [tex]\Delta\vec{p}[/tex] is the change is momentum.
    Last edited: Sep 25, 2006
  4. Sep 25, 2006 #3


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    'F = ma' is a dynamical relation.
  5. Sep 25, 2006 #4
    I was referring to "v=v0+at=> a=v-v0/t," which was then used in F = ma.
  6. Sep 25, 2006 #5


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    Sorry, I misunderstood your post. :smile:
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