Assuming you're dealing with constant acceleration, the formula is:
distance = (initial_velocity * time) + (acceleration * time * time) / 2
where
distance is the distance traveled
initial_velocity is the initial velocity (zero if the body is intially at rest, so you can drop this term in that case)
time is the time
acceleration is the (constant) acceleration
Make sure to use the proper units when calculating, i.e. meters, seconds and so on.
A very good book on the topic is Physics for Game Developers.
