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Homework Help: Unclear Format and Instruction

  1. Jul 21, 2011 #1
    1. The problem statement, all variables and given/known data
    You are on the highway travelling at 110 Km / Hr and are trying to overtake a big truck in front of you (travelling at 100Km/hr). From the opposite direction at 100Km/hour, another car is coming. Assume that you need 50 metres to overtake the truck. Approximately how far should the opposite vehicle be to allow you to safely overtake the truck in front. Calculate the relative velocities and the distances.

    2. Relevant equations
    t = d/v
    a = (v^2 - u^2) / 2d
    d = ut + 1/2at^2

    3. The attempt at a solution
    I am not sure how to go about this, so I am trying to find time, then acceleration, then distance. The way this is formatted will be greatly appreciated as I am not able to attempt it without getting confused. Thanks.
  2. jcsd
  3. Jul 21, 2011 #2
    Presumably what you are supposed to find in this problem is the distance which will prevent a collision between the overtaking car and the approaching car. So you need to figure out the time for the overtaking car to overtake the truck, and use that to find the minimum distance for the overtaking car.
  4. Jul 21, 2011 #3
    Thanks for the reply. I am not sure what equation to use since I am only given velocities, is there any other I am missing because I need another value besides velocity to calculate time. I was thinking t=d/v but I do not have distance unless I use the 50m apart that I need between me and the driver.
  5. Jul 21, 2011 #4
    ignore the other car

    how long will take you to overtake the truck?

    (If you are familiar with relative velocity concept, use it. it will be very helpful in this case)
  6. Jul 21, 2011 #5
    I see, so there are two velocities to use in the one equation, not separate and the other is car excluded from the question. Is its velocity used later or not at all? Thanks.
    Last edited: Jul 21, 2011
  7. Jul 21, 2011 #6
    to find how far that other car should be to avoid any accident :yuck: you need its velocity. :surprised
  8. Jul 21, 2011 #7
    All information given in the question is relevant. Firstly, you need to figure out the time required for the overtaking car to reach the truck. For this you need to use the velocity of the car and the truck, as well as the distance between them. Once you get this time, you need to use it to figure the required distance by using the velocities of the truck and opposite car.
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