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Acceleration problem 15

  1. Jan 30, 2007 #1
    a rock is thrown vertically with a velocity of 20m/s from the edge of a bridge 42m above the river. how long does the rock stay in the air.


    Atempt at solution:
    I've actually had a couple of attempts and i came up with a bunch of crazy things. I just need a hint, or to know if im using the correct formula.
  2. jcsd
  3. Jan 31, 2007 #2


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    Staff Emeritus
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    Iceclover, please post in the homework forums in future.

    Your equation for this question is correct. Please show your work, and we will be able to help.
  4. Jan 31, 2007 #3
    A few good helpful hints is to do this first; label what you have and what you don't have and what you're trying to find. Then look at the equations you have; use algebra to isolate a variable and these types of problems will come a lot more easily.

    Using Y's since this is acting in the Y direction, not the X direction. Also, since it's acting in the Y direction there's a force at work here =). Think about it.

    Y (final position):
    Yo (initial position):
    Vy (final velocity):
    Vyo (initial velocity):
    a (acceleration):
    t (time):

    Hint: Your starting position will usually be 0 m. Unless told otherwise through the problem. Also, you can use a string of equations to solve for things =). Such as isolate the t, and then use that t for another equation =).
    Last edited: Jan 31, 2007
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