1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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: 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..
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted