Question

A ball rolls horizontally off a table of height 0.6 m with a speed of 9 m/s .How long does it take the ball to reach the ground?

Answer 1

.35 s

Step-by-step explanation:

x = v(i)t + 1/2at^2

gravity = 9.81 m/s^2 = a

.6 m = 1/2at^2

(.6 m) * 2 = (1/2at^2)*2

1.2 m = at^2

(1.2 m)/a = (at^2)/a

0.12 s^2 = t^2

sqrt(.12 s^2) = sqrt(t^2)

.35 s = t

Answer 2

The distance an object falls from rest is

D = (1/2) (gravity) (time)² .

If the ball falls 0.9 meter, then

0.9 m = (1/2) (9.8 m/s²) (time)²

Divide each side
by 4.9 m/s² : 0.9 m / 4.9 m/s² = time²

Take the square root
of each side: time = √(0.9/4.9) sec²

= 0.43 second .

The horizontal motion of the ball makes no difference.
It doesn't matter whether the ball rolls off of a table,
gets dropped from a hand, or shot horizontally from
a gun. It still hits the floor or the ground 0.43 sec later.