Physics problem involving a falling woman...?

Question

I'm an absolute amateur when it comes to physics, and I'm failing my online assignment miserably. Could you please give me some pointers on how to solve the following problem?

"A woman is reported to have fallen 149 ft from a bulding, landing on a metal ventilator box, which she crushed to a depth of 23 inches. She suffered only minor injuries."

(A) Neglecting air resistance, calculate the speed of the woman just before she collided with the box.

(B) Calculate the magnitude of her average acceleration while in contact with the box.

(C) Calculate the time it took to crush the box.

Answer 1

A)

a = - 10 m/s^2

v0 =0;

d = -149 m;

vf^2=vi^2+2ad

vf^2 = 2 ( -10 ) ( -149)

vf^2 = 3000;

vf = 54.77 m/s

B) doing it backward for ease

vf=54.77 m/s

vi=0;

d=23 m;

vf^2=vi^2+2ad

3000=2a (-23)

3000/-46 = a

a=-65.22m/s^2

C)

a = (vf -vi ) / t

65.22 = 54.77 / t

t= 54.77 / 65.22

t = .84s