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Math Help - Projectile Problems ?

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    Projectile Problems ?

    A boy is at the window of his flat and throws a ball to his friend 24 m below. The ball is thrown with speed 10ms at an angle elevation alpha where tan alpha=5/12
    i) If the friend is standing 8m from the wall of the flat, will he be able to catch the ball without moving ?
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  2. #2
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    Quote Originally Posted by moesizlak View Post
    A boy is at the window of his flat and throws a ball to his friend 24 m below. The ball is thrown with speed 10ms at an angle elevation alpha where tan alpha=5/12
    i) If the friend is standing 8m from the wall of the flat, will he be able to catch the ball without moving ?
    My suggestion is to find out where the ball will land on the ground. If it hits the ground at x = 8 m, then the ball can be caught.

    So, I am setting an origin at the base of the building, with +x to the right and +y upward. The ball is being thrown at an angle above the +x axis.

    Let's settle the question of the angle first. We can always find tan^{-1}( 5/12) or we can simply note that sin( \alpha ) = 5/13 and cos( \alpha ) = 12/13.

    Table of x "information"
    x0 = 0 m
    v0x = 10*cos(alpha)
    x = ? (This is what we are looking for)
    vx = v0x = 10*cos(alpha)
    ax = 0 m/s^2

    Table of y "information"
    y0 = 24 m
    v0y = 10*sin(alpha)
    v = 0 m
    vy = ?
    ay = -g = -9.8 m/s^2

    The time, t, it takes for the ball to hit the ground is unknown.

    My suggestion is to find t from the y information, then use that value of t to find x.

    Can you finish it from here?

    -Dan
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