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Distance golf ball travels

  1. Jan 2, 2015 #1
    1. The problem statement, all variables and given/known data
    Golfer hits a golf ball so that it goes with initial velocity of 40 m/s at angle of 45 degrees. 100 m away is a lake that is 50 m wide. The ball will not bounce or roll when it lands. Where does the ball land?
    Before, in, or after the lake.


    2. Relevant equations
    Vertical: a = (v-v0)/t
    Horizontal: Δx = v0t+1/2at2

    3. The attempt at a solution
    I found the time as 2.8 s using the first equation by setting v = 0 (midway in flight), and v0 = 40sin45
    Then I substituted the time into the second equation along with 0 for the acceleration since there is no horizontal acceleration and v0 = 40cos45. And got 79 m, so the ball lands before the lake.
    But apparently the answer is that it lands after the lake.
    What did I do wrong?
     
  2. jcsd
  3. Jan 2, 2015 #2

    Bystander

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    This is the time for what?
     
  4. Jan 2, 2015 #3
    The time to travel halfway.
    Oh... I should've used twice that to get the total time. I get 160 m now.
    Thanks, my mistake.
     
  5. Jan 2, 2015 #4

    Bystander

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    Always try to keep in mind what information you get from a calculation, and what information you've been asked to find.
     
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