A ball is thrown vertically upward in the air from the top of a cliff. Its height above the ground is approximated by the
relation h = -4t2 +32t + 80, where h is the height in metres above the ground level and t is the time in seconds. Include
a labelled diagram showing your answer. 
a) How long is the ball above 80 m? Show/Explain how you know.

b) How long is the ball in the air? Show/Explain how you know.

 Nov 5, 2020
edited by sim51  Nov 5, 2020

To find how long the ball ia bove 80 m set h = 80 and solve for t.


To find how long it is in the air set h = 0 and solve for t.


In both cases there will be two values for t, only one of which will make sense in the context of the question.

 Nov 5, 2020

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