Question 558158
{{{h(t) = -16t^2+v[0]t+h[0]}}} Initial velocity, {{{v[0] = 0}}} and initial height, {{{h[0] = 400}}}ft.
When the camera hits the water, h = 0, so...
{{{-16t^2+400 = 0}}} 
{{{16t^2 = 400}}} Divide by 16.
{{{t^2 = 25}}} Take the square root.
{{{t = 5}}}seconds, neglecting the time it takes for the sound of the splash to travel the 400 feet to Susan's ears.