Calculating the Height of a Building Using Free Fall Time

[Medgirl314]

Homework Statement

A stone dropped from the top of a building hits the ground in 2.9 s. How high is the building?

a=9.8 m/s^2
yinitial=0
vinital=0
y=?

Homework Equations

y=1/2at^2

The Attempt at a Solution

y=1/2at^2

Plugging in what I know:
y=1/2(9.8m/s^2)(2.9s)^2
Simplifying:y=1/2(82.4) m
Answer: y=41.2 m

Is this correct? Thanks in advance for confirming! :-)

 

[Yosty22]

Looks correct to me. That is, assuming it is dropped from rest. It doesn't explicitly say, but I think it this case it is a safe assumption.

 

[Medgirl314]

Thank you! I believe it is, my physics teacher usually assumes so.