1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Physics 12 Kinematics

  1. Sep 20, 2009 #1
    1. The problem statement, all variables and given/known data
    A person driving her car at 50km/h approaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2s before turning red, and she is 30m away from the near side of the intersection. Should she try to stop, or should she make a run for it? The intersection is 12m wide, and her car's max. deceleration is -6m/s^2. Also her car takes 7s to accelerate from 50km/h to 70km/h. Ignore the length of the car and her reaction time.

    2. Relevant equations
    I don't know.

    3. The attempt at a solution
    I don't know. Please help.
  2. jcsd
  3. Sep 21, 2009 #2
    First, how much is the acceleration, when we say: if you hit the gas pedal in that car, you can accelerate from 50 to 70 km/h in 7 seconds?

    You approach an intersection with a given initial velocity, and you have to cover a given distance, with a certain amount of acceleration. Will 2 seconds be enough time? Look for a formula that includes those variables.
    Last edited: Sep 21, 2009
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook