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Projectile Motion - Time in Air

  1. Nov 6, 2014 #1
    1. The problem statement, all variables and given/known data
    What angles should an arrow be launched if it leaves the bow @ speed of 60 m/s and is trying to hit a target that is 150 m away? Assume target is same height as bow.
    Suppose the arrow is fired at an angle of 30 degrees & misses the target & hits the ground 1.8 m below from where it started. How much time was it in the air?

    2. Relevant equations
    1. t = 2vsinθ/g
    2. t = √2y/g
    3. Δy = (vsinθ)^2/2g

    3. The attempt at a solution
    I have attempted this the bold section of this problem a few different ways, but I am not convinced that any of them are correct. Could someone please tell me if any of them are correct, and if not, explain to me how to do it.

    Attempt 1: t = 2(60)sin30/9.8
    t = 6.1s

    Attempt 2: t = √2(1.8)/9.8
    t = .61s

    Attempt 3: 1.8 = (vsin30)^2/2(9.8)
    v = 8.4 m/s
    t = 2(8.4)sin30/9.8
    t = .86s
     
  2. jcsd
  3. Nov 6, 2014 #2
    Have you remembered to take into account the fact that the arrow lands 1.8m below it's original launch height?
     
  4. Nov 6, 2014 #3
    Wouldn't that be Δy, which I tried using in attempts 2 and 3?
     
  5. Nov 6, 2014 #4
    Now that you have edited your solution I believe that you are correct..
     
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