Question

A ball rows off a table with a horizontal velocity of four (ms/s). If it is 0.5 seconds for the ball to reach the floor, how high above the floor is the table top? Using g=10(m/s2)

Answer 1

Since the velocity roll off the table with a horizontal velocity this means that the vertical initial velocity is zero. Now, while the ball is falling, the vertical motion is a free fall motion, which means that we can use the following equation:

$y=y_0+v_0t-\frac{1}{2}gt^2$

In this case we know that:

• The final height, y, is zero (the ground).

,

• The initial velocity is zero.

,

• The time it takes to hit the ground is 0.5 s.

,

• The acceleration of gravity is 10.

Plugging these and solving for the initial height, y0, we have:

$\begin{gathered} 0=y_0+(0)(0.5)-\frac{1}{2}(10)(0.5^2) \\ y_0=(5)(0.25) \\ y_0=1.25 \end{gathered}$

Therefore, the initial height is 1.25 m