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kinematics - find the initial velocity

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    Could anyone please explain how to get the answer for the following question:

    A ball is thrown vertically upwards and travels freely under gravity. Three seconds later it has a speed of 4.4ms^-1 but its direction has changed. Find the initial velocity of the particle.

    S = -
    U = -
    V = 4.4 ms^-1
    A = -9.8ms^-2
    T = 3 seconds

    Keep getting -0.15 but the actual answer is 25?
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    If we break down the question into parts, it might be more useful

    (Original post by u.sha)
    A ball is thrown vertically upwards and travels freely under gravity.
    This tells us that acceleration (a) = acceleration due to gravity in the opposite direction (-9.8ms^{-1})

    (Original post by u.sha)
    Three seconds later
    This tells us that time (t) is equal to three seconds.

    (Original post by u.sha)
    Three seconds later it has a speed of 4.4ms^-1 but its direction has changed.
    As the final velocity is in the opposite direction to the initial velocity; The final velocity (v) = -4.4ms^{-1}

    (Original post by u.sha)
    Find the initial velocity of the particle.
    This means that the question wants us to find out our initial velocity (u).

    Jotting down all we know:

    s = -
    u = ?
    v = -4.4ms^{-1}
    a = -9.8ms^{-1}
    t = 3 s

    Using the constant acceleration formula v = u + at, we rearrange to make u the subject.

    v - at = u

    Then we input our values to get:  (-4.4) - (-9.8 \times 3) = 25

    Therefore, the initial velocity is equal to 25ms^{-1}
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    (Original post by u.sha)
    Could anyone please explain how to get the answer for the following question:

    A ball is thrown vertically upwards and travels freely under gravity. Three seconds later it has a speed of 4.4ms^-1 but its direction has changed. Find the initial velocity of the particle.

    S = -
    U = -
    V = 4.4 ms^-1
    A = -9.8ms^-2
    T = 3 seconds

    Keep getting -0.15 but the actual answer is 25?
    i love norogami
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    (Original post by drinktheoceans)
    If we break down the question into parts, it might be more useful



    This tells us that acceleration (a) = acceleration due to gravity in the opposite direction (-9.8ms^{-1})



    This tells us that time (t) is equal to three seconds.



    As the final velocity is in the opposite direction to the initial velocity; The final velocity (v) = -4.4ms^{-1}



    This means that the question wants us to find out our initial velocity (u).

    Jotting down all we know:

    s = -
    u = ?
    v = -4.4ms^{-1}
    a = -9.8ms^{-1}
    t = 3 s

    Using the constant acceleration formula v = u + at, we rearrange to make u the subject.

    v - at = u

    Then we input our values to get:  (-4.4) - (-9.8 \times 3) = 25

    Therefore, the initial velocity is equal to 25ms^{-1}
    omg yes yes yes this makes sense now thank you!!
 
 
 
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