We can calculate the time it takes for the ball to fall to the floor.
y = (1/2) a t^2
t = sqrt { 2y / g }
t = sqrt { (2) (0.70 m) / (9.80 m/s^2) }
t = 0.378 seconds
In a time of 0.378 seconds, the ball traveled a horizontal distance of 0.25 meters. We can find the horizontal speed when the ball was rolling on the desk.
v = d / t
v = 0.25 m / 0.378 s
v = 0.66 m/s
The ball was rolling at a speed of 0.66 m/s when it was rolling on the desk.
