Question

PLEASE HELP!!! I only have a limited amount of time left to answer these questions and I do not understand any of them.

Answer 1

Her vertical position is described by y(t). She reach the ground when y(t) = 0 so:

$y(t)=0\\\\-16t^2+100=0\quad|-16t^2\\\\100=16t^2\quad|:16\\\\t^2=6.25\quad|\sqrt{(\dots)}\\\\\boxed{t=2.5}$

She reach the ground after 2.5 seconds and she will be:

$x(2.5)=8\cdot2.5=\boxed{20}$ (meters) from the cliff.