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Homework Help: Kinematics Car acceleration Problem

  1. Aug 7, 2015 #1
    1. The problem statement, all variables and given/known data
    In the figure here, a red car and a green car move toward each other in adjacent lanes and parallel to an x axis. At time t = 0, the red car is at xr = 0 and the green car is at xg = 223 m. If the red car has a constant velocity of 20.0 km/h, the cars pass each other at x = 43.1 m. On the other hand, if the red car has a constant velocity of 40.0 km/h, they pass each other atx = 76.9 m. What are (a) the initial velocity and (b) the (constant) acceleration of the green car? Include the signs.

    2. Relevant equations

    Thank you and more power to physics forum!
  2. jcsd
  3. Aug 7, 2015 #2
    So you have one car moving with uniform velocity , and the other with constant acceleration .

    What have you tried until now ?
  4. Aug 7, 2015 #3


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    Can you find the time until passing in each case?
    Then you've gleaned all the info required from the red car and can focus on the green only..
  5. Aug 7, 2015 #4
    At the moment sir we haven't tackled this lesson but the prof gave us this problem for advance studying so I'm just posting it here in physics forum in helping tackled this problem atm I thinking if I can use the 3rd formula then I'll plug values to get equation 1? Just my 2 cents
  6. Aug 7, 2015 #5


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  7. Aug 7, 2015 #6
    Consider the initial velocity of the green car as u , and it's acceleration as a .

    So you have two unknowns . Do you know the distance that the car travels in the first and second case ? Use equation 3 .

    Hope this helps .
  8. Aug 7, 2015 #7
  9. Aug 7, 2015 #8
    Will update you sir if I can find any shed of light in this problem thankyou!
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