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Motion - Overtaking Vehicles question

  1. Mar 24, 2013 #1
    1. The problem statement, all variables and given/known data

    A car is travelling 15m behind a 15m long truck. The speed limit is 90km/hr. But the truck is travelling at 60 km/hr. the car wants to overtake the truck, and when it does, it reaches speed of 90km/hr and has to be 15m in front of the truck in order to do this. The car will be parallel with the truck (I think it means beside it in a 2 lane road). However an oncoming vehicle travelling at 90km/hr is 400m away from the vehicle. Should the vehicle overtaking overtake or not?

    2. Relevant equations

    L / (Vb - Va)

    Where L is the distance, and Vb is the velocity of the vehicle trying to overtake, and Va is the velocity of the car that is being overtaken (in this instance the truck).

    3. The attempt at a solution

    I began with:

    60 km/h = 16.67 m/s
    90 km/h = 25 m/s

    Therefore:
    Time to overtake = L / (Vb - Va)
    = (15 + 15 + 15) / (25 - 16.67)
    = 5.4 seconds

    That's all I could do. Sorry this topic is new to me and my exam is tomorrow. The teacher handed us practice questions without solutions on our last lesson. All help would greatly be appreciated.
     
  2. jcsd
  3. Mar 24, 2013 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    What is the distance the car travels in those 5.4 seconds? What is the distance the other car travels in that time?
     
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