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: Adding two lines, what is the equation of the new line?

  1. Apr 8, 2007 #1
    1. The problem statement, all variables and given/known data

    Basically I was given a table displaying speed of a vehicle, thinking distance (distance it takes for driver to react) and braking distance. I am told to find an equation relating speed of vehicle and overall distance (overall distance = thinking distance + braking distance).

    3. The attempt at a solution

    Using graphing software, I've managed to find an approximate equation relating speed and thinking distance, as well as an equation relating speed and braking distance.

    The equations are :

    For speed vs thinking dist., y = (16/3)x, where y is speed of vehicle and x is thinking distance
    For speed vs braking dist., y = 13(x^0.5), where y is the speed of vehicle and x is braking distance

    Is there any way I can find an equation for speed versus overall distance using these 2 equations that I've obtained?
  2. jcsd
  3. Apr 8, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Sure. It might be more obvious if you didn't use the same letter to denote thinking distance and braking distance.

    (And shouldn't those constants have some units on them?)
  4. Apr 8, 2007 #3
    Could anyone show me how?

    @Hurkyl: I used subscripts to distinguish the distances
  5. Apr 8, 2007 #4


    User Avatar
    Science Advisor

    You are talking about the TOTAL distance aren't you?

    (And you titled this "ADDING two lines"!)
  6. Apr 8, 2007 #5
    yeah what is wrong with that?
  7. Apr 8, 2007 #6
    Err It's ok, I've solved it. Thanks to all who read
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook