Question

a lazy 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?

Answer 1

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

So here we know that

$\Delta y = v_i t + \frac{1}{2}at^2$

here we have

$v_i = 0$

$a = 9.8 m/s^2$

now we have

$8 = 0 + \frac{1}{2}(9.8)t^2$

$t^2 = 1.63$

$t = 1.28 s$

so it will take 1.28 s to hit the water