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Motion in 1 dimension

  1. Sep 12, 2005 #1
    You are driving your new sports car at a velocity of 90km/hr, when you suddenly see a dog step into the road 50m ahead. You hit the brakes hard to get maximum deceleration of 7.5m/s^2. How far will you go before stopping? Can you avoid hitting the dog?

    I got 540m, which I know is wrong. V=0; Vi=90; a= -7.5; d=? I plugged those values into this formula: V^2= Vi^2 + 2ad. What have I done wrong? Anyone? :redface:
  2. jcsd
  3. Sep 12, 2005 #2

    Tom Mattson

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    Right here:

    Check your units. The given value of vi is 90 km/h, but you plugged it in as though it were 90 m/s. Convert the units and re-calculate. It should work.
  4. Sep 12, 2005 #3
    Okay, got it...thanks for your help!
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