Finding acceleration from 2 m fall taking 8.0 s

[imy786]

Homework Statement

density, ρ of the rock is 4000 kg m−3 and that this density is uniform throughout. You have equipment that enables you to measure the time it takes for a small object to fall from rest through a distance of 2.00 m. Your measurement is 8.0 s.

(a) Calculate the acceleration due to gravity ga at the surface of the rock.
ga is constant for the drop in the experiment

Homework Equations

t=8
ρ=4000
s=2
a=?

s=ut+1/2 at2

The Attempt at a Solution

well i can't work out the acceleration as i don't know the velocity.
Need help on this...

 

[Dick]

It says "fall from rest". What does this tell you about the initial velocity?

 

[imy786]

t=8
ρ=4000
s=2
a=?
u=0

s=ut+1/2 at2
2= 32 a
a=0.0625 m/s2

 

[Dick]

Sure, looks fine.

 

[imy786]

to how many significant figues should i give the answer to...
if i have been given time and distance to 3.s.f...should i also give the final answer to s.3.f?