calculus

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an object is fired upward at the end of the burn it has an upward velocity of 245m/s and is 14.7 m high
a) find the maximum height and when it is attained
b) when it reaches the ground

i know that i have to use the quadratic function s= -4.9t²+Vot+h

but for what i have the 4.9t² how can i use it and can help me with the problem please

  • calculus -

    For the max height, energy thinking
    top PEnergy = intial PE + Initial Kenergy
    mgh=mg*14.7 + 1/2 m 245^2
    solve for h, the maximum height.

    when is it attained?
    h=14.5+245t -1/2 g t^2 for h max, solve for time t.
    when it reaches the ground?
    h=0 solve for time.

  • calculus -

    The 4.9 is a fixed constant and deals with the force of gravity on earth.

    Your equation would be
    s = -4.9t^2 + 245t + 14.7

    take the derivative set it equal to zero and solve for t
    put that t back into the equation to find the maximum height

    b) when it hits the ground, s = 0
    so solve 0 = -4.9t^2 + 245t + 14.7 for t

  • calculus -

    great job

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