Question #8b7fa

1 Answer
Sep 6, 2015

The object is at a height of 3/4 * h34h from ground level.

Explanation:

So, you know that your object is being released from a height hh and that it reaches the ground in a time tt.

This means that you can write

h = underbrace(v_0)_(color(blue)(=0)) * t + 1/2 * g * t^2

Now, let's assume that we can stop this object's motion at t/2 and see how far it fell from its initial position h. This distance, let's say h_1, will be

h_1 = underbrace(v_0)_(color(blue)(=0)) * t/2 + 1/2 * g * (t/2)^2

h_1 = 1/2 * g * t^2/4

Notice that h_1 is actually equal to

h_1 = underbrace(1/2 * g * t^2)_(color(blue)(=h)) * 1/4 = 1/4 * h

Well, if the object travelled h/4 in t/2, then its distance from the ground is

h_"from ground" = h - h_1

h_"from ground" = h - h * 1/4 = color(green)(3/4 * h)