A rock takes 2.1 s to hit ground when it is thrown straigh up from a cliff with initial velocity of 7.5 m/s.

I need help figuringg out how yo solve this problem.

A rock takes 2.1 s to hit ground when it is thrown straigh up from a cliff with initial velocity of 7.5 m/s. Calculate height of the cliff in m & length it would take to reach the ground if thrown down with same speed.

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