Dismiss Notice
Last chance to give your feedback! Fill out the 2019 SDN Member Survey to let us know what's important to you (and win prizes!)

question regarding kinematics

Discussion in 'MCAT Study Question Q&A' started by ssjsike, Jul 25, 2011.

  1. ssjsike

    5+ Year Member

    Joined:
    May 17, 2010
    Messages:
    26
    Likes Received:
    2
    Status:
    Pre-Medical
    Hi guys, I realize that this is a silly question, but here goes:

    How long would it take an object starting from rest and accelerating uniformly at 1.5 m/s^2 to travel 3 m?

    The answer is 2 seconds.

    I understand the method of using a big 5 kinematics equation (x=vit+.5at^2), but why is this methodology wrong:?

    a=v/t
    d=vt --> v = d/t

    a = (d/t)/t --> a = d/t^2 ---> t = 1.4 seconds

    Thanks for the help everyone!
     
  2. Temperature101

    Temperature101 Membership Revoked
    Removed 2+ Year Member

    Joined:
    May 27, 2011
    Messages:
    3,487
    Likes Received:
    78
    Status:
    Medical Student
    I think you fail to realize that the d= vt is that they using the average velocity. Since the initial velocity is zero, the average velocity is v/2. Then d = (v/2)*t , which is the same as v = 2d/t; replace that in the a= v/t will yield a = 2d/t^2 and t^2= 2d/a....t^2 = 6/1.5 and t = 2. Hope it makes sense...
     
    #2 Temperature101, Jul 25, 2011
    Last edited: Jul 25, 2011
  3. OP
    OP
    ssjsike

    5+ Year Member

    Joined:
    May 17, 2010
    Messages:
    26
    Likes Received:
    2
    Status:
    Pre-Medical
    Thank you Temperature101! This definitely makes sense.
     

Share This Page