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Homework Help: Finding velocity using given angle

  1. Jul 28, 2015 #1
    1. The problem statement, all variables and given/known data:
    A body is projected with 50m/sec at an angle of 53 degree with the horizontal. After what time velocity makes an angle 33.7 degree with horizontal. (tan 33.7 = 2/3)

    2. Relevant equations: Mostly from 2-Dimension and maybe calculus.

    3. The attempt at a solution: I've first picked up the second part of the question and tried to find out the height at 33.7 degree angle by using h = uSinθt - 1/2gt but in this, I can't decide that what u should I put because 50m/sec is at the ground level. Moreover, I also don't know the time, t. And thus this method can not be used. What could be the other way? Please guide me in layman's term.
  2. jcsd
  3. Jul 28, 2015 #2
    Take into consideration that the motion consists of both x and y components (x=vcosθ and y=vsinθ). Perhaps you could try calculating what the initial speed and final speeds are for the y component. Then try calculating how much time it would take for that change in speed using your other kinematics formulas.
  4. Jul 28, 2015 #3
    Yep, that worked! I've got 2 seconds as the answer and hopefully it must be correct. Thanks :-)
  5. Jul 28, 2015 #4


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    I confirm 2 sec. (More precisely, 2.03, using 9.8 for g.)
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