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Applications of the Equations of Kinematics

  1. Jun 10, 2008 #1
    1. The problem statement, all variables and given/known data
    Please help me with this problem. If you could at least give me the formula I could probably figure it out. I have worked out all of my homework but this one.

    Please type out the formula in word form. I have a hard time figuring out what is squared and what all is under the division symbol, ex. (x= v^2 - vo^2 / 2a) displacement equals (final velocity squared minus initial velocity squared) divided by (2 times acceleration). Thanks I greatly appreciate it.

    Question:
    The left ventricle of the heart accelerates blood from rest to a velocity of +27 cm/s.

    (a) If the displacement of the blood during the acceleration is +1.9 cm, determine its acceleration (in cm/s2).

    (b) How much time does it take for the blood to reach its final velocity? (in seconds)




    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Jun 10, 2008 #2
    Work Energy theorem. Work done equals energy. (Force)x(Distance)= 1/2 (mass)(velocity)^2.

    Take mass out of each side of the equation. You have this written already, just apply it.

    Under constant acceleration, Velocity equals acceleration x time.
     
  4. Jun 11, 2008 #3
    Thanks,

    I got 192 cm/s^2 for answer to A. And 14 s for answer to B. Seems like they would have asked for time first since I used it to figure out the acceleration.

    Thanks again
     
  5. Jul 15, 2011 #4
    Actually, the time should be 0.14 s, I'm pretty sure. Here is the equation I used to calculate time: v = vo + at (final velocity is equal to initial velocity plus acceleration times time). Therefore, t = v - vo/a, which yields 0.14 s.
     
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