Answer:
The answer to your question is: t = 3.54 s
Step-by-step explanation:
data
vo = 21 m/s
height of the cliff = 44 m
t= ? when the rock be 5 meters from the water.
Process
First, calculate the distance the rock reach in its way up.
h max = vo² /2g = (21)² / 2(9.81) = 22.5 m
total height = 44 m + 22.5 m = 66.5 m
but we need to calculate the time when the rock be 5 m from the water so,
height = 66.5 - 5 m
height = 61.5 m
Now, use free fall formulas to calculate time
h = gt² / 2
61.5 = (9.81)t² / 2
solve for t
2(61.5) = 9.81t²
123 = 9,81t²
t² = 123 / 9.81
t² = 12.53
t = 3.54 s
