Alazy physics student is made to walk the plank. the plank is 8m above the water. if the plank is pulled out from under the student and he falls straight down, how long will it take him to hit the water?

As we know that it is the condition of free fall when we remove the plank below the student

So here we know that

here we have

now we have

so it will take 1.28 s to hit the water

diagram is missing, but i will try to explain your doubt.

answer:

amplitude is the maximum displacement or distance moved on a point of a vibrating body or wave measured from its equilibrium position.it is equal to half the length of vibration path.

a longitudinal wave moves energy that is to the direction of the wave’s movement. - true