Initial speed of 10 g ball thrown down from 2 m height

[Fanatic]

Homework Statement

Bill throws a 10.0-g ball straight down from a height of 2.0m. The ball strikes the floor at a speed of 7.5m/s. What was the initial speed of the ball.

Homework Equations

Can you provide the proper formula and solution to solve this problem?

The Attempt at a Solution

I tried using the following formula, but realized it was probably wrong.
vf2= vi2 +2gd
Vf and vi are to the second power
g= gravity acceleration 9.8
d- displacement

 

[Doc Al]

I tried using the following formula, but realized it was probably wrong.
vf2= vi2 +2gd

That's an excellent way to solve this problem. Give it a shot. (Careful with signs.)