A football kicker is attempting a field goal from 44m out. The ball is kicked and just clears the lower bar with a time of flight of 2.9 s. If the angle of the kick was 45 degrees, what was the initial speed of the ball?

Can you please explain the steps on how to obtain this answer, as well as, how to know which equation should be used .

Thank you so much!!! I've done it many times however, cannot obtain the correct answer

4 Answers

  • gp4rts
    Lv 7
    7 years ago
    Favorite Answer

    If the ball just clears the bar, this means that the maximum height of the trajectory is reached when the ball reaches the bar.

    The horizontal movement is

    x = V0x*t

    If the ball is kicked at an angle of 45º, then V0x = V0*cos(45º)

    The time to reach the goal @44m is

    t = 44/[V0*cos(45º)]

    if the time given means the time for the ball to reach the goal, then t = 2.9 s and

    2.9 = 44/V0x = 44/[V0*cos(45º)]

    V0 = 44/[2.9*cos(45º)] = 21.5 m/s

    If the time given is the total time the ball is in the air, then the time to reach max height is ½ the total time and is 1.45 s and V0 is 43 m/s

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  • 7 years ago

    Hmmm maybe answer is 20.5 m/s

    as this question looks to may be a question of PROJECTILE..

    Use the equation T=[2u(sinTHETA)]/g

    g is acceleration due to gravity

    u can take it 10 or 9.8

    sin theta is 45 degrees

    u is initial speed

    t is time taken

    so your ans is 20 m/s by taking g as 9.8

    hope this will help u if this question is of projectile motion...

    Source(s): My lost childhood
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  • Evelyn
    Lv 4
    4 years ago

    I'll assume your talking in grams. The formula for this equation is W= F + T W = Weight (usually SI Kilograms) F = Force (Newtons) T = Tension You will also need suvat equations to solve this (to solve the speed issues).

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  • 7 years ago

    I am not from the USA, so I don't know how high the crossbar on those poles are, but it isn't mentioned here, so I imagine that is what you are missing.

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