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Kinematics question on brakes

  1. Aug 29, 2006 #1
    Hi, can someone please check if this is right?

    A driver applies brakes on seeing a traffic signal 400m ahead. At the time of applying the brakes, the vehicle was moving with 15m/s and retarding with 0.3m/s^2. What is the distance of the vehicle from the traffic light after 1 minute?

    x = 15(60) - 1/2(0.3)(60)^2
    x = 360m

    Therefore the distance from the traffic light is 40m. Correct?
    My book says the answer is 25m. Is it wrong? Any help will be appreciated.Thanks!
  2. jcsd
  3. Aug 29, 2006 #2
    I can't see anything wrong with your work. Either the book is wrong or we're both reading the question wrong (ie: the driver starts breaking after 1 second and then breaks for a minute)
  4. Oct 28, 2009 #3
    hey BOY,
    SEE the driver has applied brakes so just calculate the time the car ll take to stop by the eq. v=u+at.Then just calc the dis by eq s=ut+1/2at^2....the dis ll be 375m.so dis from traffic light is 400-375 i.e 25 m dear.
    PARAS sir
    for further assistance contact:09810855099
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