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    A ball is thrown from a point at ground level with velocity 20ms-1 at 30 degrees to the horizontal. The ground is level and horizontal and you should ignore air resistance. Take g to be 10ms-2.

    Find the horizontal distance travelled by the ball before its first bounce.
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    (Original post by Mark Scicluna)
    A ball is thrown from a point at ground level with velocity 20ms-1 at 30 degrees to the horizontal. The ground is level and horizontal and you should ignore air resistance. Take g to be 10ms-2.

    Find the horizontal distance travelled by the ball before its first bounce.
    Resolve the velocity into it's horizontal and vertical components and use SUVAT.
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    I tried that. I got 20cos30 as the horizontal component and 20sin30 as the vertical component. I tried using s = ut + 1/2at^2, but i dont have s or t.

    Btw, the answer is 35.3.
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    (Original post by Mark Scicluna)
    I tried that. I got 20cos30 as the horizontal component and 20sin30 as the vertical component. I tried using s = ut + 1/2at^2, but i dont have s or t.

    Btw, the answer is 35.3.
    You only get 35.3 if you take g to be 9.8, not 10. So that shouldn't be the right answer given the parameters of the question.

    You know that for the vertical component, you can work out how long the ball is in the air, right? So take:
    u = 20cos30
    a = -10 (assuming + is the upwards direction)
    v = 0
    t = ?

    Now you need to use v = u + at and DOUBLE that answer, because if you don't, it only gives you the time from the ground to the air.

    Then you using the horizontal component, you know there is no horizontal acceleration, but you know how long the ball is in the air for, so take

    s = ?
    u = 20cos30
    a = 0
    t = what you got from the vertical calculation

    then distance = speed * time because acceleration is 0 here, and you should get 34.6, which is the answer if you take g to be 10
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    thnx so much i got the answer now.
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    (Original post by Mark Scicluna)
    thnx so much i got the answer now.
    You're welcome.

    The best thing to do with these questions is to draw a diagram and do things slowly. I have a mechanical engineering module in my degree and I still do things step by step slowly.
 
 
 
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