Initial velocity question

[petal5]

The question is as follows:

A man stands at the edge of the roof of a building 20.0m above the ground.He throws a ball vertically straight upwards(it just misses the edge of the building as it falls back down).If the total time taken for the ball to travel from his hand to the ground is 5.5seconds what is the initial velocity of the ball?

My question is,is it correct to use the following formula to solve the problem: x=xo + vot + 1/2at^2

Thanks!

 

[gunblaze]

Yes, it is. However, do be careful when dealing with the directions. Define ur +ve and -ve directions first.