Answer:
h = 78.4 m
Explanation:
Given that,
A stone takes 4s for the stone to touch the river's water surface.
We need to find the height of the bridge from the water level.
Let the height be h. We can use the second equation of motion to find h. So,
[tex]h=ut+\dfrac{1}{2}gt^2\\\\ \because u=0\\\\So,\\\\h=\dfrac{1}{2}\times 9.8\times 4^2\\\\h=78.4\ m[/tex]
So, the height of the bridge from the water level is 78.4 m.
