How Does Throwing an Object Downward Affect Its Fall Time from a Tower?

[caller]

Homework Statement

An object is dropped from a tower. if it had been thrown down at 60m/s, it would have taken half the time. What is the height of the tower? (Use gravity as 10m/s²)

Givens
Acceleration = 10m/s²
v₁ = 0m/s (not sure)
v² = 60m/s
time = t/2

Homework Equations

d=v₁*t+(1/2)*a*t²

The Attempt at a Solution

I tried doing the questions, but i don't understand.

The correct answer is 320m, but i don't know how to get to it.

Any help is appreciated.

Thanks

 

[Mindscrape]

Well, how much time does it take for an object at rest to fall and how much time does it take for an object thrown down to fall?