posted by Rachel .
A small ball rolls horizontally off the edge of a tabletop of height h. It strikes the floor a distance x horizontally away from the edge of the table. (Use any variable or symbol stated above along with the following as necessary: g.)
(a) How long is the ball in the air?
(b) What is its speed at the instant it leaves the table?
The answer is:
(b) (x/ SQRT(2h/g)
It's explain in this link by someone.
"A) You don't know anything about your final velocity, so you can't try to use that in the answer. The only things we have available to use in our equations are acceleration, height (distance), and initial velocity (zero, in the y direction).
We use the kinematic equation h = Vot+0.5gt2. Since Vo=0, this rearranges to t = (2h/g)1/2
B) In the first instant of the freefall, there will be no y component to the velocity, so we say that Vx=Vtotal. Next, we recall that horizontal velocity remains constant in a free fall.
So, we use the definition of velocity, displacement/time, and just plug in so that v=x/t, where t is the result you got in part A."