Question

A rock is thrown down with an initial speed of 25.3 m/s from a bridge to the water below. It takes 2.29 s for the rock to hit the water. How high is the bridge above the water in meters?

Answer 1

Height of bridge is 83.66 m

Explanation:

We have equation of motion s = ut + 0.5 at²

        Initial velocity, u = 25.3 m/s

        Acceleration, a = 9.81 m/s²  

        Time, t = 2.29 s      

     Substituting

                      s = ut + 0.5 at²

                      s = 25.3 x 2.29 + 0.5 x 9.81 x 2.29²

                      s = 83.66 m

      Height of bridge is 83.66 m