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On the average, a blink lasts about 100ms

  1. Aug 30, 2003 #1
    on the average, a blink lasts about 100ms. how far does a MiG-25 foxbat fighter travels during a pilot blink if the plane average velocity is 2500mi/h. my answer is 69.4

    what is the acceleration of a car that moves at a steady velocity of 115 km/h for 115 seconds? my answer is 115km/h. the explanation of this answer is b/c the steady velocity of the acceleration of the car is going in the same of 115km/h as it is in 115 sec.

    a car takes 14s to go from v=0 to v=30m/s at approximately constant acceleration. if you wish to find the distance traveled using the equation d = 1/2at^2, what value should you use for a?
     
    Last edited by a moderator: Feb 5, 2013
  2. jcsd
  3. Aug 30, 2003 #2
    2500 mph / 3600 (seconds per hour) = .6944444
    one tenth of that is about 1/16 of a mile in a tenth of a second.


    Steady velocity means no acceleration, (it would have to be traveling straight technically speaking)


    a= (v2-v1)/(t2-t1)

    or, the change in velocity over the change in time
     
  4. Aug 31, 2003 #3

    HallsofIvy

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    "my answer is 69.4"
    69.4 WHAT? Your answer doesn't make sense without units: miles?, feet?, meters? and thinking about how the units match up might help you see how to get the answer.

    "what is the acceleration of a car that moves at a steady velocity of 115 km/h for 115 seconds?"
    Are you sure you have copied the question correctly? At a minimum you should know that "acceleration" MEANS the rate at which velocity is CHANGING. If the car "moves at a steady velocity" then the acceleration is 0.

    "my answer is 115km/h. the explanation of this answer is b/c the steady velocity of the acceleration of the car is going in the same of 115km/h as it is in 115 sec."
    Once again, check your units. Acceleration is km/h2, not km/h. Understanding that may help. By the way, "the steady velocity of the acceleration" makes no sense at all!

    "a car takes 14s to go from v=0 to v=30m/s at approximately constant acceleration. if you wish to find the distance traveled using the equation d = 1/2at^2, what value should you use for a?"
    WHY should you use that formula. It is NEVER a good idea to use a formula that you don't understand. When you learned the formula you should have learned what "d", "a", and "t" MEANT. Knowing that, the answer is easy.
     
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